where i am going with my thinking @Van B is

1. to get this poor old girl to idle without either the decel valve or the AAV being part of the picture. neither are needed for normal warm idle.

2. to see if he can get a warm idle using the idle screw. at around 1000 rpm.

3. do the gassing thing.

trying to get this high idle thing out of the picture if possible.

realise there are a whole lot of things need for stable warm idle.
not least
correctly adjusted valves.
correctly set timing.

if it won't transition to opening the throttle from that state of warm idle.
well?
there is a few thoughts that come to mind.

also if he can't get it down to stable low warm idle and it starts to hunt around as you screw it down it could indicate there are some air leaks. and these will be unmetered air leaks. but want to get these "legit" air routes out of the picture because they are masking whether it will do a normal warm idle.

Looks to me then like the decel valve is connected opposite of mine and he hasn’t unplugged the decel line to the manifold but rather the bridge line from the intake to the valve?

See my mark ups below and tell me if I’m seeing it right?

Also, there is kink in the small line.

@Van B .

yes i noticed that kink in the small vac line to the decel.


i think he has only vac line 9 off. bridging line as you call it. and has capped off the connection points. so long as he only has that line off he is alright.

attached pic of set up for vac lines to decel.
but to be honest i don't think it matters which of the large lines you plug in either to side or end. the small line is opening the decel valve and letting the air through.
i think it can work either way, but before i say that i better double check.
(if yours is the other way around from diagram and attached photo it would tend to prove it does work either way, since your valve is operating beautifully anyway!! )
however most cars are rigged the way it is in the vac hose diagram.
attached example.
which appears to be how his is rigged.



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EDIT
but you might be on to something there with the decel.
i can't really see in to his photo clearly enough.

@tshih914 , can you take a photo in close to the decel valve so we can see it really clearly.

i just watched your video @Van B .
your decel is rigged right or at least same as diagrams and how it is normally done.

i'm looking at his and it looks the same.
from what i can see of it.
but it would be nice to see a close in photo just to be sure.

When I am hunting for a failure in the vacuum system, which has many parts, I remove all vacuum lines and tape over all the ports at the plenum.

This takes the vacuum out of the triage.
This also takes any hose out of triage.

Get the car running at idle (it needs no vacuum)
Add one vacuum line at a time, plugged into whatever device, properly.

Eventually you will create the issue again.

If you still have an issue after taking off all hoses and taping all ports closed, you could have an issue with a hole in the bottom of the plenum or your injector seals are leaking way too much.

74 L-Jetronic needs the distributor vacuum for anything but idle at operating temp when setting timing.

I just realized we haven't confirmed the turns on his idle screw at the TB!

he said he had it two turns out.
i imagine it was either already all the way down closed (which i think the introduction post said) or he at least turned it down to closed and backed it back up two full turns.

but i gather no further adjustment or attempt to bring idle down using it from there.

we probably will end up where r towle is suggesting we go!!!!

I've come in late here and haven't read all of the posts.

Several times I have forgotten to replace the connector on the AFM with the result that it would start normally but stall as soon as you hit the gas. Similar symptoms as described in this post.

Secondly, I had a problem with the car stumbling when I went over a bumpy surface or railroad tracks. I discovered that, although the AFM appeared to be connected, the connector was not seating all the way home and was going intermittently open circuit when disturbed by the bumps

On exploration I discovered that the AFM connector has a rectangular foam rubber seal around the periphery of the row of 7 pin connectors to prevent water ingress but the seal was preventing the connector from fully seating. I removed the seal and the connector clicked fully home. Problem solved.

This might be worth a look

yeah nihil we put him through that test - did not seem to be his problem.

good suggestion however to look at that seal.
his connector will be a 6 pin version.

ah. the joys of prehistoric EFI!

by the way, hows your car going mate?
got to get up to brizzy at some stage and drop in on you.

Last resort is to do a smoke test. Search on you tube on how to build one for under $20. You will find the vacuum leak.

I have every vacuum hose hooked up the same as the diagram that wonkipop posted. My photo show the 2 plugged ports to the side of decel valve and the t leading to the boot (I will be ordering a new one from AutoAtlanta as the one currently in the car is an old used one from eBay that I got when the AFM explosion triggered the search for cause of stalling after starting). I have also removed the hose connecting the two ports
as instructed for this test. The idle adjustment screw at the base of the throttle valve was adjusted 2 turns from fully closed. I did mention that while the engine was idling at 2500-3000rpm I did try to cover the air filter box's snorkel with my hand and the engine did not stall indicating that there must be a vacuum leak. When I get the new boot installed I will hunt for the source of air leak with the Smoke in a can used to test fire alarm smoke detectors.
I just reattached the hose and started the engine after many cranks to get it idling at 2800 rpm before repeating test3 and 5 (wonkipop's earlier posts). When hose to side port of decel valve was pinched closed RPM dropped by 400-500 rpm. When AAV hose was pinched rpm dropped by 800-1000rpm. The smoke in a can wasn't useful in finding the source of air leaking pass the AFM pathway.

I had a hell of a time finding a vacuum leak. It wasn't until I did a smoke test, pumping smoke into the engine that I found it was leaking around the intake manifold gaskets. The hoses could be fine, it could be the injector seals. Do the proper smoke test, it will save you a lot of aggravation. On my engine, I ditched the decel vavle and the charcoal filter.

Ok so, I checked my AFM to see what I settled on for screw turns after all my tuning before starting this rebuild. I have three turns out on the AFM airscrew and 1-1/4 turns out at the throttle body.
Every car will be a little different, but you should be in that ballpark as a baseline.

ok thats interesting @tshih914 about the snorkel.
it wasn't clear to me whether you just had your hand near the snorkel feeling for air flow or had you actually blocked it off.

yes the engine should die if you fully block the snorkel.

positives so far.
you definitely have a farked up decel.
it might come back to life with an adjustment.
if it doesn't you might still be able to source one but they are hard to get hold of.
or you can do a decel delete.

for clarification when you first did the tests i suggested, you reported the opposite results. decel dropped it by about a 1000 rpm from 3000 to 2000. AAV drop was less.
you did not give a specific number but described it as less than the 1000 drop due to the decel.
EDIT correction. went back and read the first test results. decel was 3000 to 1000. drop was 2000 revs.
AAV drop was less.

this repeat of the test seems to be the other way around/different?

guessing difference in part is due to you having the t/b idle screw out on this second test?

----

i think both of these components need to come off and be tested.

onward looking for more.

do the second smoke test.

i would also suggest a proper f p test.
i think i can see you still have your fp gauge plumbed in.
and its in the circuit before the regulator? which is good.
so you can do this test now fairly easily.
when its running you either pull and plug the vac hose into the back of the regulator or just pinch it tightly shut. the fuel pressure should be 35+/-. with the hose back in or the clamp taken off it should fall to 28. i know you have tested it and got 28. but that would have been the vac hose on value. be good info to know if its building the full pressure thats needed to acceleration/load phase.

The AAV is designed to increase idle by that amount until the engine reaches operating temperature. So, nothing revealing there just yet. I think the aspect that should be focused on right now is the non-response to throttle input.

I’ll tell you that in getting my L-Jet sorted, I replaced every old hose on that entire topside. My car was very original but what had been replaced wasn’t exactly the right size most times. Belmetric has almost all the correct hoses at a good price and wonki has provided you with his artisan diagram that I just love!

We also need to consider your fuel injectors are full of garbage and not spraying correctly or at all. Have you looked at plugs?

ps
in addition to blocking off snorkel the only other way it could pull air into the air cleaner is via the hose from the charcoal can to the air cleaner. i can see that hose is either very badly frayed in center or somehow joined. not clear. if that hose has leaks in it it could pull air via that into the a/c despite you having your hand over the snorkel.

maybe it can even pull air through the charcoal can?
anyway if i close off my cars snorkel with my hand it will die. but its not running at 3000 rpm either when i do it.

if you wanted to take that hose out of the picture for now you could pull it out of the aircleaner and plug the port on the airbox.

Yes. All these hot garbage hoses need to be fixed or else we’re shooting in the dark and wasting time.

bit by bit we are heading towards the Van B/wonki situation.

you ended up doing everything and checking everything on the EFI system as you went.
i did all of mine before we even attempted a start. the whole lot. after a 16 year sleep.
but i had mike looking over my shoulder. do this. etc. now do that. and on.
injectors, injector seals, hoses, distributor operation, ......on and on.

anyway, it should be solvable. trial and error. tick off the bits one by one.

two suggestions by other members re injector seals.
sensible suggestion.
i did mine after the sleep along with new injectors.

put them on your list to get some if you haven't done them.

another thing to get hold of is a throttle body to plenum gasket.
914 rubber has them.
worthwhile replacing that regardless. they do go hard with age.
pretty cheap little part so its not a heavy investment.

and another suggestion the plenum itself can corrode and have pinholes in it is very true.
they will likely be underneath and very had to see without getting it off.
bit of a job. notice there is a bit of surface corrosion on the intake runners.
so its a possibility.
smoke test should find them however if they are there.

Considering all recent suggestions my plan going forward is
1) replace all hoses with new (Someone posted that Belmetric sells all hoses but when I looked at their website the search under vacuum hoses gave no results) I also need to know if someone sells a complete kit that allows complete replacement of all vacuum hoses for the 1.8L L-jet (at least list the correct id and length of each hose needed.)
2) replace FI boot (already ordered from AutoAtlanta)
3)replace throttle body to plenum gasket from 914 rubber
4)fuel injectors appear to be fine as the engine was running fine and idled at 3000 rpm so may replace the injector seals which are old.
5) measure the Fuel pressure and adjust the running pressure on FP regulator 35psi and 28 psi
6) systematically go and check/test each component as per factory manual

check auto atlanta if you want a convenient vac hose kit.
i believe you specify your model when ticking the box and get all the right hoses right length.

the fuel pressure regulator on the 1.8 is non adjustable unlike the earlier D jet ones.
if its not working right its a new regulator. but don't necessarily blame the regulator just yet. check the values. it might also be that the fuel pump is not delivering sufficient pressure. i rebuilt my original fuel pump completely from top to bottom (its not supposed to be serviceable apparently but the germans forgot australians love to take things apart and make them work when its not supposed to be possible). at the end of that i tested the fuel pump independantly of the car to make sure it was making pressure and also tested flow. i was making 38 ibs out of the rebuilt pump and got the spec flow rate (delivery volume over a timed period). so insufficient fuel pressure can be down to a weak worn out old pump. basically the regulator bleeds off some of that pressure the pump makes to take it down to 28 lbs at idle. but there is no adjustment nut on the correct 1.8 fp regulator.

direct link to AA vac hose kit.

http://www.autoatlanta.com/Porsche-Vacuum-...BAAVACKIT2.html

(it was under accessories section, not hard parts, and was listed in engine misc.)

I just ordered that kit but it says the kit doesn't include the 19mm hose. So Where do I get the 19mm hose (where does this hose connect? the charcoal cannister?)

Here is the gasket on the AFM connector which wasn't allowing connector to seat home fully.

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I have been pursuing running issues and vac leaks for the past 8 months. I have used smoke machine, compressed air (as recommended by factory - Bowlsby website for this) and vacuum from a vacuum pump and a vacuum cleaner

Smoke machine:- I made one from PVC plumbing fixtures as in a few YouTube websites. Worked ok but the smoke went everywhere, it lingered in the engine compartment and it was not easy to see just where the smoke was coming from. Also, I had the machine going for too long, it overheated and melted some of the PVC - result one buggered smoke machine

Vacuum pump hand held: - intake chamber volume too large for pump and unable to pull a vacuum

Vacuum cleaner:- very simple construction. 6omm OD pvc plumbing pipe with end cap glued to pipe. Hole in end cap of a size to accommodate a grommet and the vacuum cleaner nozzle

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I used kid's bubble mix liquid diluted with a little water into a squirt bottle, applied and waited for the bubbles to appear

Compressed air:- same construction as above except in place of the grommet on the end cap I used a schrader valve to connect to the compressed air via an adjustqable regulator

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Some of the results:-

Small crack in the neck of the oil filler tower. George Hussey says in listing for this item used, that they always break. I had to get underneath with a mirror to find that one

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Both inlet manifold gaskets had cracks in them. One obviously had a washer embedded in it which caused the crack

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I bought a set of Victor Reinz gaskets which are phenolic resin with a thin gasket material applied to both sides. I fitted them and just to be sure I re tested them for vac leaks and sure enough, one side leaked. So I put a thin universal gasket on both sides of the gasket but the overall thickness was too much and I couldn't do up the nuts on to the studs. I ended up compromising by putting the thin gasket on just one side and this is working

Victor Reinz standard gasket. Note how thin the gasket facing material is

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short answer is you cannot get the 19mm hose.
though PET and my measurements say its 20mm ID. splitting hairs i know.
its the hose from the oil filler tower PCV valve to the air intake boot.
originally a formed hose to make the S curve.
people have had to do all sorts of subs and use all sorts of different hose.
you will notice on your car it has already been rigged up as elbows to solve the problem of doing the curves and sealing the junctions.
that set up you have is probably ok. if you are worried about it keep the elbows and sub new hose. probably have to find rubber hose that is hydrocarbon resistant.

love your work @nihil44

Thanks @wonkipop I do remember the old S hose was shot and I replaced it using the elbows. I went back to check the fuel pressure once I got it to start and idle at 2800 rpm. The gauge reads 28psi with vacuum hose connected and when pinched close reads 38psi so my fuel pump is working correctly.

Thanks @nihil44 for the compress air setup. I may try that.

@VanB how do you adjust the AFM (you mentioned 1-1/4 turns out in the throttle idle adjuster screw and AFM screw was 3 turns out.) Where is this screw on the AFM located?

@tshih914
beaudy. at least we can tick off the fp as A O K.
regulator and pump.

See the little hole near the front right off the AFM? That's your air bypass screw.

Thanks, now for my case is there any point in messing with that screw when it appears I already have some air bypassing the AFM?

Also since my decel valve appears to be farked up and there are no replacements has anyone opened one up to see if they can repair the damage?

i probably wouldn't play with it at this stage.
its a new rebuilt AFM and theoretically should be about right.
but then again @Van B might have something to say.

i have never had to fool with mine.

i don't think you can open a decel.
its the sort of thing i would do of course.
attacking a fuel pump was a lot of fun.
but only with a spare to replace it.
i take the attitude destruction is likely.
i kind of looks like it would be pretty hard to get back together.
however there is a guy in australia who apparently rebuilds these things and other vac devices and has proper equipment to open up the crimping seams etc.
if it is farked up and won't respond to adjustment it will very likely be the diaphragm that is rat sh#t. so its pretty hard to fix unless you feel like becoming one of those kinds of experts.

Have you adjusted the decel valve or tested it to see what vacuum its opening at?

Also, they are still out there. You just gotta know what to look for:
https://www.ebay.com/itm/403375849459

@wonkipop quit being so scared to that mean AFM. All he needs to do is confirm how many turns out he is on the bypass screw… we’re just confirming baselines on the system.

Just for the hell of it I google search " schematic of Bosch L-Jetronic decel valve" and came up with hit on last years' 914world post

http://www.914world.com/bbs2/index.php?showtopic=342479

Read all 3 pages and it appears that a 911 decel valve may be usable as a last resort. but the tests for proper function is given by GregAmy:

Testing the decel valve is fairly straightforward. With no vacuum on the port, the valve should be closed and you can't blow through it. Adding a vacuum via a Mity-Vac and the valve should open and you can blow through it. As I recall the desired setting for that cutover is 17mmHg?

If you can blow through it when it's off the car, and/or cannot blow through it with vacuum on it, then it's bad and/or out of adjustment. I wouln'dt be surprised if a prior owner danked around with the adjustment...

If it works fine but the cutover vacuum is either too high or too low, then it can be adjusted via that locknut and screw to ~17mmHg.

What are your current symptoms when testing in this manner?

Thats too low IMO. I posted the link to my thread on post #29 on your thread here.

Ever check the boot after installing the afm?

I wonder what is the diaphram (redline in schematic) made of rubber or metal? If rubber then age will lead to hardening and cracking

No I have a new one coming from AutoAtlanta that I will install along with new hoses and gaskets

Diaphragm is rubber. It gets hard and less flexible, but the spring is what wears out and what causes the required adjustment. Lots of movement and heat cycles over the years.

If you’ve read my thread, I was having high idle issues when running and idle hang when driving.

IMO, you have a whole collection of maintenance issues from deferred maintenance over the years. None major or you wouldn’t even get a high idle and smooth running.

I think your biggest issue is it not taking throttle input.

its the only bit i am genuinely terrified of.

the rest of it i just tear into it.

agree with you, this poor baby has a ton of deferred maint. items that have all built up.
and its been tweaked along the way at various points to make it idle /whatever.
its finally accumulated to be "all too much" for it.
progress can be made when all hoses/seals are verified as non leaking and associated vac/electrical "gadgets"/ignition items tested and confirmed as spec operational.

yeah @tshih914 . i am the guy with the last post who has found himself a 911 decel valve. it is indeed perfectly useable. you just adjust it to the vac levels with Van B's research info as a base to set it to, and adjust if necessary after test driving.

the only difference in the decel valves is that the 911 ones may have been adjusted to a different vac level than 914 and they had the bracket brazed on a different angle.

i still have not done an install of my 911 decel, as i run it without the decel.
i actually have a fuel pressure valve subbed in and all the hoses run to it.
this is the same as blocking all the hoses off except it looks legit.
i think the first owner installed it back in the day as a state of maryland emissions cheat.

i enjoy the way the car snaps off throttle.
there is no danger of a backfire through the induction system with the car properly timed and tuned. the most it does is drop unburned fuel into the exhaust system and i hear soft bangs and burbles out the muffler. the unburned fuel goes off in the hot muffler.

very occasionally if i give it a bit of stick and fiddle the clutch as i am manouvring out of my "garage" down over my "non cross-over" 19 th century bluestone curb it will momentarily die for about 1 second and then burst back into life. the AFM flapper has bounced back beyond the fuel pump contacts and it cuts the fuel until it resumes position. decel valve in part is designed to stop that - slows and cushions the return of the AFM flapper back to near closed - as well as being a useful emission device to stop pathetic juvenile minds like mine being amused by exhaust pops and dumped hydrocarbons.

that only applies to L jets. i hear the decel is a little more essential to the long life of one highly desirable and difficult to procure part in the D jet set ups.

@tshih914

i knew i had this filed away but couldn't find it my L jetronic files.
eventually stumbled on it again.

could be helpful.

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combine this with the factory w/shop manual.

here is the rest of it.
its an idiots guide.
which i was 5 years ago and likely still am.

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Well the new boot and throttle gasket was delivered yesterday so I replaced the old today. I also noticed that my air filter was badly mangled at one edge but after I replaced it with new one no difference in engine response to gassing it(stalls).Click to view attachment

When after many attempts to fire up the engine starts to idle at 3000rpm. I pinched off the Aux air valve and the rpm dropped to 1200, when I release the clamp the idle goes back to 3000. When I put my hand over the snorkel I feel no air moving into the AFM (its adjustment screw is covered by a rubber plug to discourage tampering after it was rebuilt.

When you pinch the AAV hose, and the rpm drops to 1200, does the car take throttle? Or does it still stall?
Also, when you’re doing all this have you ever let the car warm up to operating temp?

One other thing, I’m not understanding how you just noticed the air filter, I thought we talked to you about pushing the afm flap with the key on to see if your fuel pump kicks on?