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> 1974 1.8L engine fast idle then stalls, Fuel injection issues
wonkipop
post Mar 12 2023, 12:39 PM
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QUOTE(tshih914 @ Mar 12 2023, 09:26 AM) *

My fuel is OK as I have been very mindful as a chemist and have used fuel preservatives like Marine Stabil and I've replaced the plastic lines with stainless steel ones and installed all new fuel hoses. It is very possible my injectors are not working will have to pull them and test.

As far as our future use of fossil fuels and fuel quality concerns, those farking A-holes in power around the world (especially in USA) have been bought and corrupted and compromised by China CCP to force everyone to join the cult of Climate change and Marxism.

The new breed of electric cars are soulless and boring would much rather play with our old toys.

I have posted a short video on my channel showing the current resting state of my AFM showing a slight gap at the door which I was closing using a flat blade screwdriver. Is that gap (2-3mm) supposed to be completely closed in a correctly adjusted AFM?


dunno.
i have not been poking around in my AFM for at least 4 years.
i'd have to get the air cleaner off to have a look.

-----
re injectors and question of where fuel is coming from the engine runs on at present.
there is a very quick test you can do with the state the car is in.
bypass the cold start injector.
it should be in line in the circuit between the right and left banks of injectors.
undo the fuel hoses to it. then join them together. sleeve it and clamp or if you have nothing to sleeve them together maybe a piece of leftover fuel hose from your replumbing. use that to join the left and right hand banks and by pass the cold start injector.

fire it up. see if anything changes. like does it go.

---

you will be taking the injectors out to do the seals soon.
will be an opportunity to observe the injectors.
get them all out but leave them connected to fuel circuit.
stick the nozzles into 4 small bottles.
those really small plastic bottles that water comes in are handy.
they seem the right size to perch down there in the engine bay and then you can usually get the injector nozzles to nicely fit into them to spray.
that will tell you if they are all spraying.
just crank the starter. they should all fire if they are any good.
you can crank it for a bit. say 20 seconds or so.
see if the same amount of fuel is in each bottle.
see if they are spraying equally.
its a kind of rudimentary test.
but it will at least tell you if they are working.


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technicalninja
post Mar 12 2023, 12:55 PM
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Smoke test is a good idea at this point.

I had one last year that threw me for a loop.

550K 2000 Toyota T100 Tacoma, 4-cylinder 5 speed.
1 owner from new. No engine problems ever. On original clutch.

Had 1 injector go bad 20K in past, lost another 3 weeks before the problem.
Changed all 4 with real OEM Densos (hard to find).
Injection was L-Jetronic style with upgrades that happened due to 25 years of technology changes.
L-Jet with MAF, waste spark, real potentiometer TPS, O2 sensors, OBD2 but still simple batch fire injection.

Truck is run 150 miles per day from Granbury to Southlake for work. Owner has been doing this forever.
Truck runs fine on freeway but anything below 40 mph it's a sick chicken. Bucking, snorting, an absolute bitch to use stop and go. NO Idle at all. Seemed possessed.
Fuel pressure 5 psi below normal. Changed regulator. Fuel pressure normal but didn't help the issue. No check engine lights or codes in memory.
Did a bunch of diagnosis to no avail. Figured out that a brand-new $4K Snap-On Solis scan tool could not see live data actually live. It had a 5 second delay in reporting data.

Decided I didn't have a scan tool that was quick enough to actually see what was going on in "real time" or maybe I'm a moron and cannot diagnose FI problems anymore.
Charged customer for FPR and 1 hour of diag time. Spent 2 days fighting this beast.
Super good customer that brings me ALL of their cars and all of their friends and extended families cars.
"A" class people, the type of customer that keeps your business alive. Horrible to say "I can't fix this" to this type of customer.
Leaning towards bad ECU but I've never had a bad ECU Japanese car that would actually run. Bad ECU=dead puppy in my book.
I "ate" this one big time.

Referred them to Toyota Dealer with the hope that one of the old dogs at the dealership had more direct experience with these than me.
One of the 20+ year techs had two of these himself, shitloads of experience and he could use his two trucks for swap and check diagnosis.

$1300 later they figured it out.
They swapped everything including my brand-new injectors. Nothing helped it. They swapped all the old stuff back into truck.
They finally did an ethanol test of the fuel and found 42% ethanol...
Not 10 or 15%, they found 42%.

Drain and re-fill gas tank fixed this truck completely. It was the root of the issue.
The gas looked and smelled fine, and it was less than a couple of days old, but it was still bad.

After the diag was complete the customer told me he's been filling up at the same gas station for 20+ years but there was an accident at the gas station that day and he was forced to fill up at a different station just before it did this crap.

I should have questioned the fuel from the start. It was a screw up on my part.

Current fuels cannot be "stabilized" with additives. Unless you can do a full lab analysis you should not trust fuels over 6 months old.

Lots of my customers who own classic cars use race gas in them. This fuel, with no ethanol or "green" additives can last 5 years but it costs over $10 per gallon.

Nest door to me is a big Lawn Mower dealership. They are about to hit their busiest season as spring brings massive fuel issues because the mowers have been stored for the last 4 months not in use. 33% of their yearly business is cleaning out old pump gas from fuel systems.

The OP has not said how old the fuel is, just that it is good.
I don't trust fuel anymore; it has made me look like an idiot too many times...


Watched the videos. The TPS looks fine, my AFM flap does not have the play at rest that the OP's does. Mine is ancient and has not been rebuilt.
One thing, I'm not sure the tach is accurate. It's hard to tell via a YouTube vid but it sounds like 2K when it shows 3.5k. I'd verify the tach is accurate with an old school engine analyzer. I have a 40-year-old Craftsman DIY unit that can give me dwell and RPM readings. I pulled it out from a 30-year hibernation to check dwell on my ignition the other day. I've almost thrown it away a couple of times and I'm glad I kept it now.

From the run vids his injectors are delivering fuel IMO. The 7 min long video kills the idea that he's running on the cold start injector in my book.
After starting the cold start injector could be disconnected to prove this. I think it's running on all 4 injectors now. You can listen to the injectors "click" with a mechanic's stethoscope but I'm betting they all are. You can kill the cold start injector by disconnecting it or by disconnecting the thermo-time switch.

The vid that shows the resistance change via the AFM flap almost looks like that drops out (seeing infinity) at different points in its travel. This would cause major issues and might be the source of his trouble. I use little jumper cables with tiny little alligator clips so I'm not trying to hold the leads on the pins in the AFM when doing a resistance check to verify I don't have a bad spot on the AFM printed circuit board. The resistance change should also be a slope with no dropouts to infinity or direct continuity ever.

Hope this helps.
I am very interested in what the root cause of this problem is.

The info I've posted makes it look like I hate ethanol...
This is far from the case.
E85 or E100 is a super fuel that is dirt cheap. It's equal to 105-110 octane racing fuel when run in modern systems that are designed and mapped for it. The final engine in my current 914 will have modern digital EFI and E85 will be my "preferred" fuel for it.

What I don't like is the addition of 10-15% ethanol in normal pump gas. It doesn't help anti-knock at that level, the corn used for production increases the cost of pretty much everything in the grocery store, and it doesn't clean up the tailpipe emissions at all as the fuel economy drops enough to offset the gains via increased overall mass in the exhaust.

In gasoline it sucks, as a stand-alone fuel it's rocket fuel...
Even at 85-100% its long-term storage life sucks big time. Ethanol needs to be brand new in my book.
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wonkipop
post Mar 12 2023, 01:35 PM
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@technicalninja

i just watched his 7 min film.

hmmmm.

certainly interesting.

fricken weird.

i'd have to think about it.

i note it managed to hit 4K revs at one point there racing away.
and he got it to drop to 1200 clamping off the AAV.
but it seemed a bit all over the place.
not quite consistent.
would have to watch it again and look closely at what revs were at different times he had both hoses on. i guess that could depend on just how tightly a hose was clamped off each time. but it did seem at one point as if it was doing 3000 rpm with both hoses connected and at another point 4000. ?

yes i doubt a cold start injector stuck on with nothing else injecting would deliver 4K revs.
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wonkipop
post Mar 13 2023, 07:33 PM
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@tshih914

i watched your clip again a couple of times.

right just keeping it simple.

1. cold start problem.
put that aside for the moment.

2. fast "idle" racing problem.
put that aside for the moment.

3. the big one. it won't take applied throttle.
you can overthink this sometimes.
i just watched the video with an open mind.
its not getting fuel.
plain and simple - the fuel just cuts out.

why?

not sure.
but it is most certainly connected to it knowing the throttle has been opened.
two ways that happens.
the TPS sends the signal (or stops sending the signal more accurately) for idle.
the AFM takes over.
(until you hit wide open throttle).

i still think the screw up is in there somewhere.

something is happening where once the car comes off the idle position on the TPS, it goes looking for the info from the AFM and its not there so it just shuts it all down. closes the injectors off. when you take your foot off the throttle immediately the minute it begins to stall the switch comes back on again and so does the fuel. and the engine just manages to come back to life. leave your foot on there too long or double pump it and its a stall.

i don't exactly know how. you have checked the TPS switch. and you have checked the EFI harness for integrity. so ????

but it seems very clear to me that its getting fuel (might be running like a mad banshee) but its getting fuel while the throttle is closed.

and as soon as that switch comes off, no fuel.

i don't think its a fuel mixture problem. like leaning out.
its a absolute mixture problem. its all air? (IMG:style_emoticons/default/biggrin.gif)

like technicalninja says, don't think thats down to blocked injectors.
they seem perfectly capable of propelling things to 4000 rpm.
they could be a bit shitty but not so shitty i think that they would suddenly fall over.


i have not had a chance to run into mike yet to see if he had any clues.

-------


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Van B
post Mar 13 2023, 09:49 PM
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Too be clear fellas, the injectors don’t have to be blocked. If the flow rate increase turn the injector into a stream, it won’t atomize correctly and the car will stall… and also smell very rich.

But I’m not certain thats the issue either, just a theory.

In post #1 he says, car would stall with throttle, then messing around he blew the AFM and had to replace it, then ran normal, then racing idle and stall with throttle again?
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wonkipop
post Mar 14 2023, 03:07 AM
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QUOTE(Van B @ Mar 13 2023, 09:49 PM) *

Too be clear fellas, the injectors don’t have to be blocked. If the flow rate increase turn the injector into a stream, it won’t atomize correctly and the car will stall… and also smell very rich.

But I’m not certain thats the issue either, just a theory.

In post #1 he says, car would stall with throttle, then messing around he blew the AFM and had to replace it, then ran normal, then racing idle and stall with throttle again?


its a good theory.
not discounting it.

the trouble shooting issue i believe condenses down to this.

car will start and idle.
stalls when throttle opens.

subset two of trouble shooting.
car is difficult to cold start.

i believe having watched the video that it may be possible to make this thing idle.
the moment where he crunched the line to the AAV and it dropped to 1200 was an eye opener!. i am still processing how it can run at 3000-4000 off an AAV and a decel. (IMG:style_emoticons/default/biggrin.gif)
and then squeezing one line it dropped to 1200. hmmm.

i'm going to take all this to mike and ask him. casually when i next get to the workshop to continue adventures in 1984 thunderbird land. (i actually like working on the thunderbird because it always make me think of chief crazy horse, my favorite indian warrior when i was a kid. his warpaint was all about the thunderbird. rain on one cheek lightning bolt on the other. the indigenous mob in america were cool cats (IMG:style_emoticons/default/smile.gif) )

like @technicalninja i think i want to know what the root cause of this debacle is.

i still have not interrogated the full history of exactly how this emerged.
when.
and in what sequence.
i mean did @tshih914 wake up one morning and it just had all gone to sh$t when he started it. i don't think so. but we can get to that. what happened along the way to here. (IMG:style_emoticons/default/beerchug.gif)
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wonkipop
post Mar 14 2023, 03:25 AM
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i am actually interested in @tshih914 's car.
same month of production as mine.
about a thousand vins before mine.
same gorgeous brown vinyl.
same brown carpet.
teamed up with green. he has the @StarBear combo.

its a little more worn.
but examining his engine bay photos surprisingly intact.
tune up sticker is still there all in one piece.
i even spied his emission sticker in one post.

i think he needs to tell us more about this car.
where he got it.
his plans for it.
its an L jet.
i know he wants to supersede that and go all fako 2.0 d jet...........but.

all in good time.

and i watched his video having fun at watkins glen.

so ...........happy to try and sort this problem.
the car has my sympathy. (IMG:style_emoticons/default/beerchug.gif)
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wonkipop
post Mar 14 2023, 02:38 PM
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QUOTE(Van B @ Mar 13 2023, 09:49 PM) *

Too be clear fellas, the injectors don’t have to be blocked. If the flow rate increase turn the injector into a stream, it won’t atomize correctly and the car will stall… and also smell very rich.

But I’m not certain thats the issue either, just a theory.

In post #1 he says, car would stall with throttle, then messing around he blew the AFM and had to replace it, then ran normal, then racing idle and stall with throttle again?


ok.
i can see how that can happen.

throttle closed theoretically fuel pressure is down at 28lbs with vacuum from plenum. throttle opened, vac comes off, fuel pressure rises to 35lbs.
he has confirmed he has those two pressures.

with you theory it floods due to injector flow rate changing.
wet plugs would confirm that if he shut it down straight after he induces a stall rather than letting it recover and run. immediately pull the plugs and inspect.
as i note you have previously suggested.

only time injectors do have decreased flow rate is at idle and at deacceleration after throttle closes. so it does fit the scenario. open throttle fuel pressure rises, flow rate increases, spray pattern goes to sh#t. ok.

his only real way to confirm the injector behaviour is to take them to a specialist for testing and with luck cleaning.

this business with high ethanol content in USA fuel could induce pintel corrosion if you lay the car up for long enough. it is hygroscopic. if the pintels are corroded its throw them away time. they never come good even with attempts to clean. any relief is temporary.

fortunately here fuel with ethanol (which is permitted up to 10%) must be labelled E10 and we still have wide availability of petroleum without the blend.
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tshih914
post Mar 14 2023, 04:45 PM
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i think he needs to tell us more about this car.
where he got it.
his plans for it.
its an L jet.
i know he wants to supersede that and go all fako 2.0 d jet...........but.

all in good time.

and i watched his video having fun at watkins glen.

so ...........happy to try and sort this problem.
the car has my sympathy. (IMG:style_emoticons/default/beerchug.gif)
[/quote]

Here's the story of my 1974 914-1.8L. I bought it from a person who lived in Manhattan NYC who advertised in craigslist during circa 2000? He was asking $4000 and the car was not running because the alternator warning light was lit and he thought he needed to get a new alternator. I suspected that it could be that or the belt had broken and I asked him how much it was costing him to keep the car parked at his apartment's garage. He said his monthly garage fee was $350 and that his mechanic said it would costs him about $1000 to replace the alternator. I made him an offer of $2500 for the car and he took it after I told him if he doesn't sell the car in another 3 months he would be worse off than selling it now for $2500.

When the car was towed home to NJ courtesy of AAA I discovered that it was indeed only a broken fan belt which I replaced for $50 and it ran like well without issues. I drove the car as a weekend toy as I had a 1990 Honda Civic base hatchback 4speed manual daily commuter. The body was in very good condition except for the battery tray having been replaced due to acid damage and some minor structural rust along the back lower valance area that I repaired by welding (badly) pieces of steel to cover up any holes and gaps between rust through. The dash has a crack which was covered over by a plastic cover and it looks decent enough to not be a problem. I was not content with its performance compared to my 1st 914 (a 65,000 miles 1974 Signal Orange 914-2.0L w/appearance group) which I had purchased used for $6000 in 1979 while at Caltech getting my PhD in chemistry. I had a desire to perhaps upgrade my 1.8L L-jet to the more reliable and higher output D-jet 2.0L. I searched and found a 1975 2.0L which was F/S because it also was in a state of disrepair (broken fuel lines spraying fuel all over engine bay when attempted to start and the body was very rusty. I bought it for $1000 in 2003(?) and stripped it for the parts (engine with complete F.I., 901 gearbox side shifter, set of anti-sway bars and door handles). I then sold the rolling chassis to some kid who wanted to make 1 good 914 from 2 chassis for $650. The engine after being stripped down to the split case halves and crankshafts in 2008 is finally being reassembled with brand new 2.0L Mahle pistons and cylinders new rod bearings and main bearings, rebuilt heads, new NOS stock Porsche camshaft and modified swivel feet adjusters (valve train).
The interim period where my 1.8L was parked due to lack of attention since I had many other Porsches to drive and enjoy started to develop a hard starting problem. This was indeed due to being parked for over several months with fuel that was going bad due to the switchover to ethanol in place of MTBE. The reason ethanol is bad for cars that run well on pure gasoline is it soaks up water over time and gets oxidized to gummy polymers and wreaks havoc as our friend techninja had described. Being a chemist I am well aware of this problem so I have been careful to make sure the gas in my tank is well preserved with Marine Stabil when stored after my having to rebuilt my blown AFM.

The whole thing about using ethanol in gasoline is the result of complete political capitulation to the corn lobby as it is scientific lunacy to add something that is completely unnecessary for the efficient and clean operations of the internal combustion engine. The idea of adding an oxygenated additive was to aid in the combustion process when carburetors were crudely metering out fuel in the 1970s. Today's ICE can burn all HC fuels completely to CO2 and H2O without the fuel having any oxygenated additives. A gallon of pure gasoline produces the maximum amount of energy and goes the greatest possible distance compared to a gallon of pure ethanol of anything else (E10, E85, etc).

The whole Climate/global warming existential threat is a complete hoax and cult to destroy the American global dominance and cede every advantage to China.

Getting back to my problem I will do the injectors test for flow and spray pattern soon in the upcoming weekends and report back.

P.S @wonkipop The car at Watkins Glen is a 2020GT4 (grandkid to the 914?)
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wonkipop
post Mar 14 2023, 07:56 PM
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@tshih914 .

cal tech man. i'm impressed.
and driving a 914 back then. man of taste.
my business partner is a chemical engineer.

-----

ok i spoke to mike finally.

here is what you do.

now that we have discovered the AAV and decel issue they must now be taken 100% out of the mix for further trouble shooting.

pinching the hoses is not adequate. thats merely a initial test to note that you can lower the revs closing them.

1. pull decel hoses as previous test. plug them at the ports with 100% sealing plugs.
the decel valve is not to be hooked up again while the trouble shooting work is being done. it is not required for this work.
you can reinstall it later if you succeed in adjusting it properly. at the end of everything else. we know this drops the revs 400-500 going off your video.

2. pull and plug the AAV hoses. mike did not think that the huge drop in revs you were getting at times by clamping it was out of order. cold it is wide open. and since we know its stays wide open the warmer the engine gets the faster it can run on the fuel being made available to it.

3. in consideration of the hard starting you could start the engine and warm it with the AAV connected if this helps to start it. then stop the engine. disconnect and plug the AAV at the ports and the hose. probably most convenient where it connects to intake duct.

4. ensure the timing is correct. this can be done statically. it is surpsingly accurate if set this way. so long as you know what you are doing. if the timing is out, setting it statically will get it closer to where it ought to be than where it is now.

5. check the points gap. it is essential that the points are clean and set precisely.

6. check that the accelerator cable is not pulling the throttle plate even open slightly when you have it connected up. ensure that throttle plate is completely back at rest on its stop and not being even cracked open a little bit.

7. what you are going to be doing is manipulating the AFM flap by hand with your fingertips while the engine is running. in the case of a 914 due to the air cleaner design and AFM location you will find it best to unbolt the AFM from the upper aircleaner it is attached to but still connected to the air intake boot. you need to be able to get your hand in a comfortable position to be able to gently manipulate the AFM Flap for what is ahead. it will probably be necessary to get the rest of the air cleaner out of the way/

8. it is essential that the idle is lowered as far as possible for this exercise.
there seemed to be promise that with those hoses effectively plugged and engine fully warmed it might drop as low as 1200 rpm. if its still to high - say 2000 rpm try and bring it down by adjusting the idle screw on the throttle body. do it in small amounts.
and give it time to settle between each small adjustment.

9. play with the throttle in the engine bay. get used to finding a comfortable position where you can manipulate it very gently opening it small amounts and opening it slowly.
do this with out the engine running. just find out how you can position yourself.
what you are going to be doing is manipulating the AFM flap with your left hand and the throttle with the right hand while leaning into the engine bay. so you need to work out where to position the AFM and prop it and where to position yourself and do all this.

------

A after timing is set, points checked, decel definitely out and plugged. start the car with the AAV still connected if you think this will help. let the engine warm for at least 5 minutes. if you want to control it a bit and lower revs pinch the AAV hose shut and just let it run as low as you can get it until its warm. you will feel the engine heat and know its hot enough.

B. switch off. disconnect AAV and plug the hose and port 100%
restart. hopefully it can without AAV assistance once its warm.
if necessary lower the idle further if its still high at say 2000. get it down as low as you can. it might go unstable due to further air leaks we haven't found yet. ie it will lean out. just back it back off again if it does. go for as low as you can get it to be.

C. once its idling at whatever you can it to. hopefully somewhere down there between 1200 and 1500 its time to play with the AFM. push it in very gently and very slowly very small amounts. what you are doing is tricking the ECU to deliver more fuel.
you are changing the mixture. we want to see if the ECU is getting the AFM signal.
the throttle will still be closed and we will have taken the major air leak routes out, so the revs and tone of the engine should change if the AFM is working and also communicating.
remember very small manipulations. you will get the hang of it and can play around a bit with it.
if it does respond we go to D.
i have always been uncertain about this bit as i believed the throttle position switch controls the mixture at idle. and it does. but mike says, like Van, that if the AFM flap moves far enough it will provide info too. usually it does not at idle because it is not being pulled far enough to override the idle circuit in the ECU.

D this is where you are going to crack open the throttle and play with the AFM at the same time. now you don't want to open the throttle wide and suddenly. you want to crack it open and hold it open a little bit. and then if it falters push the air flow flap a small amount as well. see if you are able to keep it running. if you can keep working up the scale. a little more throttle - a little more AFM flap.

-------

why are we doing this.
its to see if in fact @Van B is right.
Van is basically saying this thing has a mixture problem in very crude terms.
its not getting anything like enough fuel out of the injectors once the full pressure comes on. EDIT - more properly Van is saying its not getting its fuel delivered in the correct way as an atomized mist pointed in the right direction as well as possibly not giving the full flow rate at throttle open fuel pressure. but you can trick it to prove this.

mike agrees with Van. he is not saying this is necessarily the cause but the above test will certainly tell you whether it is or not and it will also affirm the AFM is working and communicating.

the problem you have got is you are way up there in revs at the moment at "idle"
and then you are wanting to open the throttle and the AFM is actually at a point lower down the rev mountain (in terms of fuel and air). so we need to be doing this test from a point where we climb the rev mountain if possible with the throttle rather than fall off the cliff if that makes sense.

anyway this test is going to tell you a lot.

it might take you a few attempts to master this given the fickle state of its idle and its cold start problem.


----

as to cold start difficulty.

timing. timing. timing. points gap. points gap. points gap.
and is the cold start injector working.

-----

as to badly spraying injectors.
not just flow rate.
i got a lecture on where the injectors might be pointing whatever spray pattern they make. correctly functioning injectors are pointed directly at the back of the valve where it seats. vaporization in a warmed engine completes the job atomization has done.
if they are spraying anywhere else at other surfaces fuel won't vaporize effectively.
etc etc. unhealthy injectors can produce a whole series of difficulties of which Van B is only hinting at because he knows what it all means just like mike does.

------

see how you go with this.
at least you will be able to feel confident with your AFM after this if it works.
and also your AFM to ECU connections.


-----
As an aside L jet is as reliable as D Jet and far simpler.
Its just a matter of making sure all the components are working to spec.
running well an L jet is real sweet in my humble opinion.
not that there is anything wrong with a D Jet 2.0 either.
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tshih914
post Mar 18 2023, 11:42 AM
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I started to follow your test and have posted some new short video on my pfan12000 youtube channel. I managed to get the idle down to about 1200rpm and at step 7 was about to do the static timing check of the points under the distributor cap and remembered that a while ago I had replaced the mechanical points with a Pertronics electronic ignition system (see photo below). So unfortunatelyafter shutting off the engine I was not able to restart it to get it to idle at 1200 rpm before testing the AFM/throttle position switch. I believe that the electrical ignition system is normal but the problem most likely is going to be localized around the AFM settings. In my attemts to restart the engine I was loosening the idle control screw at the base of the throttle housing and was still not able to get a sustained 1200 rpm idle even with the screw completely out.


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Jason74914
post Mar 18 2023, 03:49 PM
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Are you using factory high pressure fuel pump or something with similar pressure and liters per minute?
Are you sure the input and return lines to the pump are properly installed?
High idle sounds like vacuum leak (smoke test) or bad AFM.
Cutting out over 3k rpm sounds like fuel delivery issue. Not enough pressure and/or flow rate.
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Jason74914
post Mar 18 2023, 03:55 PM
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Just saw your last posted. Inability to restart after it was running could be fuel pressure regulator, which holds fuel pressure for a while after you shut down so that you hav some on restart. But vacuum issues also affect FPR.
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wonkipop
post Mar 18 2023, 04:11 PM
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QUOTE(Jason74914 @ Mar 18 2023, 03:49 PM) *

Are you using factory high pressure fuel pump or something with similar pressure and liters per minute?
Are you sure the input and return lines to the pump are properly installed?
High idle sounds like vacuum leak (smoke test) or bad AFM.
Cutting out over 3k rpm sounds like fuel delivery issue. Not enough pressure and/or flow rate.


thats what we will find out with the test i have given him to do.

he has got good fuel pressure and it is correct (with both vac line to FPR off and on).
but it is an interesting point (re return lines etc). i don't know if he has an original three port fuel pump. all we know from his replies is it has been shifted to the front and it is direct wired in to run when ignition is on, rather than stock set up with fp run off the AFM flapper contacts and dual relay).

it did have big leaks. they were through the decel and the AAV so were metered air that was affecting the AFM flap. these appear to have been the primary leaks.

it may still have other leaks but these will be unmetered leaks.
he has been given suggestions of where they commonly will be and to replace various seals. ie injector seals. etc.

-------

i watched video @tshih914 .
it almost sounded normal. (IMG:style_emoticons/default/beerchug.gif)
so at least we know with that decel and AAV taken out 100% you can get it very close to normal idle. and that these are the major sources of the air leak side of things.

to restart you may have to reconnect the AAV.
warm it if it will start.
disconnect.

points gap and static timing were to be done before you started the engine again.
don't know petronix. someone who has it can comment.
i guess point gap is non issue.
static time it is all you need to do. or check the static timing.
timing sounds like its very close to correct listening to that video.

-------

if you can get it restarted and get it idling like that again then you will be able to get to the point of doing the AFM and throttle manipulation test.

the idea of that test is to tell you if you may well have a fuel delivery problem with the injectors.


EDIT

ii just took a very close look at the photo you posted @tshih914 .
have you noticed that the green vac line hose is disconnected from the back of the distributor retard side of the double vac can.

did you just knock this off getting distributor cap off? or has it been off the whole time?n (IMG:style_emoticons/default/confused24.gif)

this is another air leak. your engine will be pulling in air via the vac port on the throttle body through that hose.

this is unmetered air.

that hose has to be reconnected.

i've seen people disconnect that retard vac line and therefor disconnect vac retard.
not sure thats a good idea, but theoretically it can be done.
but you would have to either plug the hose or plug the port on the throttle body.
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tshih914
post Mar 18 2023, 04:38 PM
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The green hose was connected during the whole time engine was running. It was disconnected when I took the cap off to show you the Pertronic ignition system.

https://www.motortrend.com/how-to/1404-pert...nition-systems/

above website explains the replacement of traditional points and condenser with electronic ignitor
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wonkipop
post Mar 18 2023, 04:43 PM
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QUOTE(tshih914 @ Mar 18 2023, 04:38 PM) *

The green hose was connected during the whole time engine was running. It was disconnected when I took the cap off to show you the Pertronic ignition system.


ok
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wonkipop
post Mar 18 2023, 04:50 PM
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@tshih914 .

the point is you are making progress.
using elimination.
dont get distracted. don't shot gun it.
lots of comments come in here that are well meaning but have not read the whole thread. its 10 pages!

just do the test with the AFM and the throttle - if you can restart it and get it going again.

report the results.

--------

the hard starting issue can be looked at later.

it could be a separate problem or it could be related to the issue of injectors.
we will get to that rationally.

----------

don't assume anything about the AFM yet.
its a new rebuilt unit.
we have to assume its good for now.
given that you report the car did run well for a time with it installed.
but later developed these problems we are addressing one by one.
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wonkipop
post Mar 18 2023, 07:29 PM
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@tshih914

watched a couple of the other films which look like some newer ones you have put up since i last looked.

one in particular.

so looks like you had it down at steady 1200.
so this must have been after you managed to adjust idle with AAV and decel 100% out.

then you must have resumed with AAV clamped off with vice grips.
it was sitting at 1200.
then you were gently applying throttle directly by hand on t/b.
and it was dying as you gently opened up throttle.
correct?
but if you backed off the small amount of throttle quickly it resumed.

and then you unclamped the AAV and it died.

if you can get to that same state again and start manipulating the AFM flap to see what happens it will be interesting.
you need to disassemble the AFM meter from the upper part of plastic aircleaner so you move the flap with your fingers easily and in small amounts. it will be too hard trying to poke a screwdriver at it with any sort of dexterity.

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technicalninja
post Mar 19 2023, 10:16 AM
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I just take the black plastic top off of the afm to manually operate it.

Now, back in my Z car days I ALWAYS kept a known good AFM as a test item. It's buried in 10K lbs. of Z-car stuff right now...

A couple of days back I tried to "slope" my not-proven good 914 AFM.

As the test in the past, it doesn't really slope accurately.

I never see infinity or continuity through it but the resistance values vary back and forth across the range so right now I cannot say that testing an AFM with a DVOM is a good way to verify operation..

Sorry I couldn't be more helpful with bench testing an AFM.
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wonkipop
post Mar 19 2023, 02:53 PM
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QUOTE(technicalninja @ Mar 19 2023, 10:16 AM) *

I just take the black plastic top off of the afm to manually operate it.

Now, back in my Z car days I ALWAYS kept a known good AFM as a test item. It's buried in 10K lbs. of Z-car stuff right now...

A couple of days back I tried to "slope" my not-proven good 914 AFM.

As the test in the past, it doesn't really slope accurately.

I never see infinity or continuity through it but the resistance values vary back and forth across the range so right now I cannot say that testing an AFM with a DVOM is a good way to verify operation..

Sorry I couldn't be more helpful with bench testing an AFM.


this test i have told him to do will tell him enough to zero in on it.

he should not need to open the black plastic top on the AFM.
you can operate it easily once its off the air cleaner.
four bolts. no need to break the AFM seal.
also if the need arises to return the AFM it will also be clear he has not tampered with it.

one of two things are going to happen when he starts manipulating the AFM.

1. nothing.
that means either his AFM, his EFI loom, or his ECU is kaput in some way.
he has tested the loom at the plugs and it seemed to be ok.

2. something. the engine will respond.
which means his problem likely lies somewhere else.

it really is looking to me like there is something wrong in the AFM, the loom, or the ECU having watched his video where he had the revs down to 1200 and very gently opened the throttle. when it comes off that idle switch in the throttle body it really feels as if its a no signal situation.

but the test i have told him to do will point to that if its the case.
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