My 1.8L 914-4 with stock Bosch L?-Jetronic FI after being stored several years started to develop a hard to start problem. When finally started would stall when I give the gas pedal any input to raise the revs. I suspect there was some kind of intake air leak and while fiddling around had a backfire which blew the AF meter which I had Pelicanparts repaired. After replacing the fuel lines with the stainless ones from Tangerine Racing and flushing out the fuel system with Techron the engine started to run normally for a short time. Now the engine can be started and fast idles at 3000 rpm but again any input to rev up the engine results in stalling. The idle adjustment screw at the base of the throttle housing is fully closed. Any suggestions on how to fix?

Check to make sure your AFM is plugged in first.

sort of sounds like its not connected maybe?
moving throttle plate takes throttle position switch off idle position and hands off to AFM.
except AFM might not be there.

check that first.
then troubleshooting step by step can commence.
sounds like this problem was already there before you had unfortunate backfire and wrecked the AFM. kind of pointing at maybe a problem in the harness? or somewhere in the hand off between the TPS and the AFM.
anyway its got to be done methodically.


fast idle is likely a separate problem. maybe.
one step at a time.
save that for later.

what 1.8. 74 or 75?

1+ on the AFM not being connected. Check for vacuum leaked. The intake boot may have a crack.

I assure all that the AFM is plugged in and my fuel pressure gauge reads 28psi. One other piece of info is when the engine is "idling" at 3000 rpm I placed my hand to cover the nozzle of the air box housing feeling for vacuum from the air passing through the air filter into the AFM and felt little air flow! This means that there is an air leak (like when you adjust the idle by opening the screw at the base of the throttle to bypass the AFM). I had replaced the intake boot when the initial problems showed up. When searching for vacuum leaks there are lots of hoses and connections and even the O-ring gasket under the oil filler cap to check. Also is there an auxiliary air flow sensor in the 1974 1.8L FI system?

for the hell of it check the throttle body boot for cracks

Would a vacuum leak down stream of AFM result in a low idle not a high one?

thats been my experience.
air leaks usually mean it won't idle at all or it will have an unsteady idle and hunts around. air leaks won't pull the AFM flap, so usually they lean out.

@tshih914

these are handy if you don't have them.
factory workshop manuals.

http://p914-6info.net/Manuals.htm

you may as well download them all (except 914/6 specific).
fuel injection = group 2.
has all the trouble shooting checks for each L jet component.
its a bit tricky to read as its mixed in the with D Jet stuff.

back to high idle, i suspect this is the decel valve.
its come up before with two other members.
fits the pattern. idle stuck at 3000 rpm.
i'd have to dig up the thread.
but @Van B can probably find it easily, he was the original poster for one of them.
or he can lay out the precise process for testing the decel valve to see if its good,
and also to adjust it. the decel valve is adjustable.
its diaphragm has probably stuck.
the air route through the decel valve will pull the AFM flap and let the ECU know its wanting the fuel to match the air. even though the throttle position switch is letting the ECU know the throttle is closed and at idle position. in other words it is perpetually stuck at halfway down from open throttle to closed throttle.


accurate vacuum hose layouts are here on page 3 of this thread.

http://www.914world.com/bbs2/index.php?sho...57407&st=40

for 74 models.
you can check your vacuum hose set up just to be sure.
but i don't think its going to be an air leak that is causing the high idle.

there is no auxiliary air flow sensor in the L jet.
but there is a cold start aux air flow valve. AAV.
provides extra air to the engine during cold start.
but its connection is in the boot and after the AFM flap.
so it causes the AFM flap to deflect and for the car to receive extra air bypassing the closed throttle. there are two other sensors to measure temp. the main one at a cold start is the cylinder head temp sensor telling the ECU the engine is cold. i doubt the AAV will cause of the 3000 rpm high idle. it will raise the idle if its stuck open but not usually to that extent. not from stone cold anyway.

its a matter of downloading the manual and testing each component methodically 1 by 1.

i'm not sure exactly what is causing the engine to die when you gas it for revs.
apart from the AFM not communicating properly with the ECU.
i've got some other L jet diagnostic manuals. i'll look through them to see if thats a specific fault mentioned. as you mentioned - you had this fault initially before AFM explosion. so its something there you have not found yet despite the rebuilt AFM unit.

i don't want to speculate too far, but one of the components on the check list will the throttle position switch. i'd have to read further on what that might lead to if its faulty or not operating correctly.

You covered the snorkel completely and the car kept running??

Here check this out to help you at least get a baseline on your connections:

https://youtu.be/ToxifurNXXg


https://www.youtube.com/watch?v=ToxifurNXXg

@wonkipop What alerts me is the no change in idle with the snorkel completely covered. I made that video because this thread reminded me that I should post this up for future reference.

Let’s confirm connections first and then see what’s working and whats not.

@tshih914 , the high idle started after you made repairs to the car? You said in your original post that it ran normally for a bit. What happened between then and now?

i read that as feeling around for airflow at snorkel rather than putting his hand over it and closing it off? engine should die if its closed off i agree.

nice little video. all there.
its an EC-B too.
with the vac advance line from distributor to throttle body.
EC-A won't have that. nor a 49 state 75. just the retard vac line in those.

Yeah, I know, but I don’t care about California emissions lol

just in case @tshih914 has got a retarded (nation of california) engine and sees a hose that isn't there thats been holding him back for 50 years.

we need to stick that video over in the 1.8 thread in originality.
its 101 L jet vac hoses for compleate idiots and 100% correct,
for idiots like me 5 years ago.

i noticed you carefully waved your hand in the general direction of the "dreaded"charcoal can!

All the above; L-Jet requires that there are no vacuum leaks. I found the small hoses were first to go, even a T connecting them became brittle and broke.
To test the small hoses, try bending them between your fingers. That’s how I found the leaks.
Subsequently, I placed an in-line Vacuum gauge in one of the larger hoses

@Van B

thinking about his problem there are two tests he can do right now without fiddling with anything or altering things as they stand. given the engine starts and fast idles at 3000 rpm. its obviously getting fuel at crank and at idle. and plenty of air.

1. before starting check the operation of the throttle valve. move it around by hand and make sure it is moving freely and resting right back at closed position.

2. start it up and let it settle at its 3000 rpm.

3. clamp off the vac hose tightly shut between decel valve and intake plenum.
note what happens if anything. does idle change. (make sure you clamp the right hose, its the one that comes out of side of decel valve and goes to intake plenum EDIT - sorry it comes out of end of decel and goes to plenum - it operates the valve off vacuum, but thinking about it you can also clamp off the hose that comes off side as its getting the air from the intake boot, so either of those can be clamped off shut).

4. unclamp hose. let engine return to 3000 rpm if it did change.

5. clamp Aux Air Valve hose tightly shut between end of AAV and intake boot.
(clamp it before it gets to the Y junction into boot as you want to isolate the AAV. - the other hose off Y junction is going to the decel valve).
note what happens if anything. does idle change.

Refer excellent video by prof Van B of hoses posted above to know which hoses referred to.

report results of 3 and 5 back here.

------

Boy does that all sound familiar.

I’d still like to know what changed from when it ran normal.

it does sound a bit familiar, but not completely the same.

he said he left it to sit in storage for a few years.
something in there gave up the ghost during rip van winkle period.

they don't like sitting around.


EDIT - i seem to recall you ( @Van B ) got some weird thing where your 1.8 would run at 3000 rpm and not do anything else when you had something off. but its a couple of years ago and i can't find that thread anymore. maybe its my imagination and false memory? there was something i was asked to do by you and i think it was see if mine would start and run without the AFM plug in. mine would not. but yours would? and it was the way the fuel pump in yours had been wired in after moving to the front. mine is still stock and fuel pump is run off the AFM contacts after cranking phase. i could have this wrong. but yours would run and it ran at 3000 rpm? until you hit the throttle. my memory is not that good.

EDIT EDIT - can you see where i am going with this @Van B ?
we have to find your thread again and go through it.

BTW @tshih914 - thats not the fuel pressure test for L jets.
you are going to find the correct test in the links to the manuals i posted previous.
you are actually looking for 35ilbs pressure when you operate the AFM flap.
its all in the manual. you can also test flow which is important as well as pressure.
again all the manual. but that is jumping ahead at this stage.
you need those manuals. the fuel pressure regulator is non adjustable in the L jets.

@wonkipop . What he described is exactly what happened when I started the car and forgot to plug in the AFM. Steve tried it and the same thing happened for him. You tried it and it didn’t work. That’s when I realized my fuel pump wiring was wrong as yours was OE and Steve and I had a different setup from the relocation to the front.

yeah -
see my post above where i edited it. memory recall was coming back.
i'm getting old and my ECU is a bit hard to fire up.
but i was remembering you did something exactly like this.

i'm thinking his pump wiring is letting the engine run because it does not need the AFM contacts operating at idle to do it.

and i'm thinking that maybe his EFI plug and harness from AFM to ECU is possibly kaput.
like despite being plugged in its not actually connecting.
so as you gas it its all over. all air and suddenly no fuel.
the ECU is not opening the injectors. no signal?

would pull those plugs out at both ECU and AFM and given them a good clean first of all.
checking for corrosion. then i guess test it all as per factory manual.

@Van B

which is to say as i suspected that high idle at start is not directly connected to his other problem. yeah its running at idle and weird but if it was factory set up it would not run at all. which is his real problem. if i recall correctly what mine did with plug out was fire up into life and then die immediately. as you would expect with original wiring of fuel pump to only run on crank and then hand off to AFM as soon as it fires and moves the flap, just that little bit that opens the fuel pump contacts.

which is why i think its not a vac leak that is his problem. (though never say never completely).

the real symptom to investigate in a trouble shooting manual is --->starts, then immediately dies and will not idle. as is noted in original post as the first sign of trouble some time back--------> before undertaking additional work? on fuel system? etc.

question for @tshih914 did you do anything to fuel pump in your work doing fuel lines after the problem initially presented with difficult start?

Go to Jeff Bowlsby's web site
and get the Ljet fuel injection wire harness diagrams. Get a test light and check the continuity of the wire harnesses.

reckon the only thing that will cause that is a sticking air gate in the AFM,most normal air leaks will cause a high idle of say 1500 but generally not more but not 3000.
I had this with one of my old BMW's after top overhaul and found the AFM was full of crap,run great after a good clean,same system but the 914 AFM is known to suffer issues after backfire of I'am thinking that's happened.
Cheers.

You might also check the quality of the contacts in the harness connector to the AFM. Bent? Gapped? Corroded/dirty? It’s very common for the old original contacts to be worn out by now, negatively affecting connectivity . The contacts are two cantilever springs that separate due to 50 years of metal fatigue, in addition to dirt, corrosion and others contamination causing deteriorated connectivity.

yeah though this is even weirder and its something @Van B discovered.

it could be internal to the AFM like dirt, corrosion.wear on contacts etc.
but @tshih914 does have a new/rebuilt AFM now. i would think its probably pretty ok in those terms.

@Van B is on to this one i think.

if there was ever an argument for preserving a car in original condition - and by this i mean technically, not just aesthetically, it was during his relentless program to get his 1.8 running right. he knew i had a pretty unmolested car. so he kept giving me scenarios to try on mine. we didn't get the same outcomes. eventually between us all we cracked the fuel pump wiring trickery.

it sure is weird. but if that fuel pump is wired to the ignition circuit and it stays on, the car will run with the AFM disconnected from the ECU. but only with the TPS closed in idle position. no other position. and however it does it, it runs it at elevated revs.

and if its factory original wiring to fuel pump it won't run. it will fire, but it won't continue to run.

yes.
and you are the man who would know.

@wonkipop

When I pinched off either one of the 2 hoses from the decel valve to the intake plenum the idle dropped from 3000 to closer to 1000 rpm. (result of 3)

The idle also dropped when AAV hose was clamped (result of 5.)

Whatever you have back there by the batter near where the decel valve should be is not the correct part. If that thing is opening at idle, it will surely cause a high idle.

Edit: here is a thread of mine about the decel valve.
http://www.914world.com/bbs2/index.php?s=&...t&p=2956383

Leave the Aux Air Regulator/Valve alone for now as it should be open until the engine is warm.
But if what I’m seeing back there on your second picture is the AAV setup, its a hot mess and probably a big part of your problem.

@van B
Lol the hot mess near the battery is indeed not stock. When I replaced the fuel lines I used the braided hoses to connect the steel lines in the tunnel to the non-stock metal fuel filter inline to the remnant plastic line feeding the engine fuel rails (temporary hook up since I intend to stick a 2L rebuilt engine when done in place of the 1.8L currently in place). That mess is not any vacuum hose causing/relating to my high idle issue.

Ok. Glad that thing wasn't some decel valve rip off. So, what you can do next is take off the decel valve and adjust it. I went through that in the thread I posted the link to. You just need a vacuum gauge.

Got rid of all that shit, the decel valve and the charcoal canister.. Just have a hose from the oil fill neck to the throttle body boot and kept the auxiliary air valve.

Keep the decel valve as long as it's functional and you can set it properly. It should help extend the life of the MPS diaphragm.

no mps in a L-jet. so decel is not as critical as it is in D jet.

however agree with you, there is no need to get rid of the decel valve.
@Van B has successfully adjusted one to the correct level.

but this is not his real problem?
his problem is the car only starts and runs at this idle level and dies as soon as he gases it.

the decel valve is elevating the idle level for sure.
if it was adjusted correctly idle would drop.
but.......it would still have the problem of not running once the tps switch comes off idle.

test would appear to indicate that the AAV is working as it should. maybe.
i imagine the engine was still cold when he did this test for us.
eventually it would probably have closed and the 3000 rpm would have dropped slightly. later on he can test his AAV to make sure its closing properly.
but not critical at this stage.
its not his real problem.

he can now move on to the next test which i have described in further post.

Curious. What kind of condition are the oil fill tower gaskets in? Replaced?

ok @tshih914

@Van B (i'm sure) and i would like you to do one more test.

pull the AFM plug out (you can pull it out up at the AFM unit on the aircleaner) and see it if starts and runs at this 3000 rpm. don't touch the gas pedal. just let it start on its own.

if it does start and run do a second thing.

turn if off, restart it without touching the gas pedal or throttle and then once its running again at this steady 3000 open the throttle to give it the gas and see what happens. again with AFM plug out.

report back on the result.
-------


thanks for including the photos.
i am studying them trying to look at area between battery and firewall.
it looks like your ECU is not securely fixed but floating around in there.
its been rotated 90 degrees.
not that its necessarily the cause of your problem,
but @Van B (and i) are thinking of your ECU to AFM connection.
the test i have asked you to do is going to see if this is the problem.


-------

i can see from photos how you have rigged up the fuel lines.
looks fine. i can see most of your vacuum lines and they look right and looks like you have gone over them. i can even see the intake runners appear to have new or good condition woven seals. so all that looks pretty good for being tight and leak free.

its a good idea inserting a full flow high pressure fuel filter in the line like you have.
i have one too which i have installed in almost the same spot.
will save your injectors if you have a newer type fuel pump and it detonates internally.

which leads to the next question.

when this problem of more and more difficult starting first was happening, where was the fuel pump and what was it. original type pump under engine bay on rhs? with original electrical connection?

and did you install a new fuel pump with all your work on the fuel lines.
if you did, where is it, what type and how is it wired in to run?

@wonkipop if the decel valve is full flow, it could still make the car stall as soon as he touches the gas because you're just introducing even more air into an already excessively lean scenario.

that said, I agree that this symptom is way to similar to what we learned about how the engine acts when the AFM is unplugged/dead and the fuel pump is DAPO wired.

yes agree re the decel valve/lean scenario.

test i have suggested is another easy one to do without jiggling or mucking about with anything much.

just methodically ticking it off.

he should definitely go and adjust the decel valve following your instructions in thread you linked to. but before he takes if off and does that, just to run this test.

and tell us how the fuel pump is wired.

it won't exactly nail it down to the ECU connection.
but i'm thinking about how he reported the problem initially arising.
progressively more difficult starting.
then it dying when he gassed it.
to me this is the real problem he has?
that could point to either poor contacts in the AFM unit itself or a dodgy ECU/AFM connection. progressive degeneration of an electrical contact? he has a new AFM now, so its unlikely to be internal to that.
but the other two parts could still be the issue.

he has subsequently done more work on the fuel system.
so now it appears to start ok, but run only at idle.
so something did change.
we both know how that can happen if the fuel pump is not wired OE.
it can and will start easily. with that plug out. when it should not.
but it won't do much else.
i guess i am interested in whether his work in between has resulted in this easier start.
but thats all its resulted in. and its a bit of a smokescreen.

and perhaps most importantly in between these two states of affairs it seems it ran fine for a while!!!

lets see.

i'm also looking at that ECU which is very evident in photos to be in a less than desirable state of affairs. perhaps he has just disconnected its mounting as he undertakes this work. but its not great.

---------

after he reports back we could also get him to run an easy test on the decel to explore your suggestion. even before he adjusts it he could take it out of the equation by pulling the hoses out of it. and plugging the hoses. it should still start i think, even without all that air its getting from the decel - but start and idle lower.
he can then give the throttle a tweak and see what happens. ie does it die once it comes off TPS or will it respond to throttle and not die.

but i am thinking one step at a time.

do test i suggest above in previous post first.

then do the decel valve delete test second.

ok
@Van B and @tshih914

i found Van's topic regarding the way the car will run with the AFM plug out.

link to the page.
goes over next 3 pages.

http://www.914world.com/bbs2/index.php?sho...6678&st=320


mine with OE wiring of fuel pump (runs when cranking and then runs off AFM flap which moves enough at idle to open the fuel pump contacts) would crank and fire and run for about 10 seconds from a cold start. conclusion was it was running off cold start injector.
after that on repeated starts it would crank, fire for a second and die.


starbear's with non OE wiring of fuel pump (pump on whenever ignition on).
good condition AAV. good condition decel.
would crank, fire and run but die after a longer period of time than mine.
repeated starts led to repeat of cycle except it ran at idle on its own for longer each time with revs gradually rising.
eventually getting out to running for 40 seconds.


van's with non OE wiring of fuel pump similar to starbear.
started with high idle (1400). slowly rose to 2000 rpm this was when the car was still suffering from a poor low idle at cold due to the non functioning AAV. but after a non functioning decel valve had been corrected. ran happily at high idle. van blipped throttle and it died. started it a second time and it repeated the effort.
van noticed the next day his AFM plug was out. plugged it back in and car started normally with its usual poor/low idle from cold.

as a result of this accident, wonki and starbear were asked to see if they could repeat what van's car did. see results above.

from this we worked out that if the ignition circuit was running the fuel pump an L jet would start and run in a strange way without the AFM plug. but only if the ignition circuit was running the fuel pump. wonki car with OEM wiring needed the hand off between the cranking circuit running the f p to the AFM flap which kicked forward and opened the contacts to run the fuel pump. no hand off with the plug out. so it dies instantly.

none of them would run once you kicked the throttle open as all of them were looking for the AFM signal once the throttle comes off the throttle position switch at idle.

this is the condition we want to try and tick off the list for @tshih914 .
to do this we have to work out what is running the fuel pump at start up.
is it ignition circuit modification or is it still stock.

The fuel pump is the original one that came with the car. Its in the front of the car under the fuel tank next to the brake master cylinder protected by the steel panel that,s bolted to the A-arms front torsion bar area.
I unplugged the AFM and the engine started after several attempts and started to idle around 1200 rpm initially then rose to 2000 rpm. Shut it off and upon restart while at 2000rpm try to give it gas it immediately stall. All the while unplugged so no AFM input

wow @tshih914

that was a quick test and reply.
we are making some progress.

first thing. fuel pump may be original or original type.
but its definitely not in stock position for a 74 L jet.

would appear its had the by now common modification of a move up to front of car under fuel tank to guard against vapor lock.
(the original stock position is right under the engine on right hand side tucked right up above the heater tube that goes into the longitudinal).

given the behaviour after you unplugged the afm its definitely not stock OEM wired in. i'd say its running off the ignition circuit.

i'd have to think about this a bit.
no doubt @Van B will come in again at some point.

but the behaviour with the AFM unplugged was not exactly the same as with it plugged in by the sounds of it. i would have expected it to be exactly the same if the fault or problem was that the AFM was not sending a signal and the car was just running off the fuel pump triggered by the ignition circuit and the throttle position switch at idle.

i'd probably think at this stage there was a signal getting through.

i'm going to go with the idea that the AFM signal is not a problem.

you should turn to the second test now.
pull the hoses off the decel valve and plug the hoses so it can't pull air.
try starting it. it should go. and idle should be reduced to level it was when you clamped the decel valve. but you might find the idle air screw is too closed and you might have to adjust that to get it to idle. its been getting a lot of air through that decel valve. but its not "leaking" air. it is actually metered air. it will have been pulling the AFM flap open. the AAV will have too. so this is not an unmetered air leak.

and then try gassing it after you have got it idling.
this should be a good test for @Van B 's thinking its falling over because it leans right out the minute you open the throttle.
see what happens and let us know.

Definitely sounds like the AFM is doing stuff… but also, you can’t have that idle screw all the way down. You won’t idle like that. Put it two turns out and leave it there till you’re ready to set it up correctly.

Ref the video I made for you, remove the vac hose on the decel valve that runs from the side of the valve to the manifold. Block off the manifold and the port on the decel valve. Leave everything else connected for the moment.

Give it a start and lets see how it behaves.

Also, please post up your door placard so, we can confirm your mfg date.

Did as instructed I opened the idle adjustment screw 2 turns and after cranking a bit the engine started with a rough idle then stayed around 2000-2500 rpm. Again when gassed the rpm drops to almost stall but when I release the throttle it would idle back up to 2500 rpm. After 2 stabs of the throttle it finally stalled. I 've included the photos of the blocked off manifold T and side of Dcel valve along with the door label showing a Jan.1974 build date.

@tshih914

we are getting somewhere.
this time it did not stall, it almost stalled, but did not stall.
it did try to do the transition to open throttle.
not very well. but it showed hopeful signs!

the first time you sealed off the decel hoses it dropped to 1000, much lower than the 2000-2500 with this test. that was because in the first test the idle screw was closed completely shut. the engine was getting a significant portion of its air from the decel valve. to the tune of about 2000 rpms worth. now some of that air that was being supplied by the decel for the elevated revs is being supplied by the idle air passage being opened up.

the auxiliary air valve is probably supplying some rpms worth going by the tests.
when you pinched that one shut in the earlier isolation test you said the rpm dropped but you did not say by how much. if it was in proper working order it would have been in the order of 400-500 rpm worth stone cold. getting less as it warmed up and closed.

from here you really have to go through each component one at a time and test them.
you will need that factory manual i gave link to in page 1 of this topic.
you only need section 1 (engine) and section 2 (EFI).

it will be interesting to hear from other members.
there are some very knowledgable L jet guys on the site.
@Van B will likely have something to say now that could be useful.

i'm going to think about it a bit more.


EDIT
thanks for the VIN label. its built the week before mine.
got the same brown interior.
when we get to the end of this and hopefully get the old girl running i'll ask a favour of you for some archival info, but not now, lets get her going.

@tshih914

The decel valve is on the other side. I can’t exactly see what you’ve done in the photo but I see an open hose. Is that coming from the aux air regulator?

Yeah this is all wrong. You’ve got the wrong part. You capped off the Y where it attaches to the aux air valve/regulator inlet, but then left the AAV open… which is allowing unmetered air into the manifold.

You need to put all that back together.

Watch my video again and go over to the passenger side and find the decel valve. That’s what we’re trying to get capped off.

@Van B .

i think he has got it right.
he seems to have removed the hose between the decel valve and the Y junction.
the route for air to be drawn into the decel valve.
and he has capped the decel valve and the Y junction.
which means the decel valve can't draw air and the boot is sealed.
thats if i am reading his photo correctly?

i don't see any uncapped hoses to plenum in the photo.
so long as he has taken the hose out i understand he has it should be isolating the decel and stopping the air route and not leaving anything open.



Click to view attachment

i think he has pulled this hose out and capped the Y and decel at where it joined them.

Click to view attachment