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> 1974 1.8L engine fast idle then stalls, Fuel injection issues
tshih914
post Mar 22 2023, 07:54 PM
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[OK just uploaded my 6 min 29 sec video of the AFM and throttle test on my pfan12000 youtube channel. View it and open for comments
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wonkipop
post Mar 22 2023, 11:58 PM
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not entirely clear what you did watching that film.

test was.
1.
first push the flap without touching the throttle.
did anything happen?

2.
manipulate throttle along with AFM flap and see if you could keep it going?

you will need to fill me in that this is what you did.
and if so -

what happened at 1?

i think you were doing 2 for most of what i was watching on film.
didn't look like you could keep it going.

without you reporting on 1 i can't tell you what you are looking at here.






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tshih914
post Mar 23 2023, 05:42 PM
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QUOTE(wonkipop @ Mar 22 2023, 09:58 PM) *

not entirely clear what you did watching that film.

test was.
1.
first push the flap without touching the throttle.
did anything happen?

2.
manipulate throttle along with AFM flap and see if you could keep it going?

you will need to fill me in that this is what you did.
and if so -

what happened at 1?

i think you were doing 2 for most of what i was watching on film.
didn't look like you could keep it going.

without you reporting on 1 i can't tell you what you are looking at here.


Sorry wonkipop, I forgot to establish a baseline idle of 1200rpm before playing around with the AFM flap. At the end of last weekend's attempt after getting the 1200 rpm baseline idle after engine had warmed up and plugging all manifold openings connecting the AAV and decel valve I noticed that the hose plug going to the rear of the decel valve had popped off so I used a hose connector this time to connect the manifold hoses together. This time the car started on the first attempt and reached about 3000 rpm which dropped to 1800 rpm when I disconnected the hose to AAV.

I just tried to repeat test 1. after establishing an 800 rpm idle. You can see video at 3:52 and around 6:20 I was able to raise rpm to around 2000 by moving the flap of the AFM . When trying to move throttle along with the flap the stalling occurs but the engine can be restarted immediately. The video is uploaded on my youtube channel it's about 8 min long.

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wonkipop
post Mar 23 2023, 08:52 PM
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great

i watched film.

i believe there is nothing wrong with your AFM - you just proved it. test 1.
its communicating with the ECU.
mind you thats an opinion but that is what i believe.

what you are doing there is basically commanding more fuel.
but if its all healthy leak wise it should not be getting additional air to go with it. so its a tricky little operation where you have to have a deft hand.
you did the test well.
it will want to flood the engine which it sounded like a couple of times.
but you managed to be sensitive enough with it to raise revs with the available air flow to prove the AFM is in action.

it raised revs a fair bit. more than i thought it would. will talk to mike.

second.
you have proved what is playing a big part in sending the idle sky high.
defective AAV. responsible for a fair whack of those elevated revs.
probably to the tune of 1200 worth when its cold and running enriched off the ECU at cold start.
defective decel valve. looks like its worth up around 800 rpm worth in same situtation.
you will have to find a way to get a fix on that.
there have been suggestions in relation to both items.
with them out of the picture and well sealed off, and a bit of tweaking on the idle air screw (with additional tune up, ie valves and timing) there should be no reason it won't idle steady at the spec rate of around 900 + or - 50.

your throttle body needs re-examination. in particular the tps.
i'd be concentrating on that to see if it can rectify the situation.
but i'll wait to speak to mike.

the car also sounds a ways out of tune.
sounds like it needs a valve adjustment.
timing set properly.
plugs checked, cleaned or replaced.

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wonkipop
post Mar 23 2023, 10:04 PM
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mike just rang me.
so i spoke to him.
recited the rev rise you got out of the AFM from the low idle of 800.
you said you got it to 2000 pushing in the AFM.

his comment, (and he would know) is you still have significant air leaks.
you managed to give it fuel and there was sufficient air to support 2000 rpm.
he feels if the system was leak tight you would only get a rev rise of about 50-100 rpm before it fell over with a gentle push of the afm.

so you are still chasing other leaks in his view.
since you have new hoses etc.
there are three main places left.

the intake runner gasket sleeves that connect to distributor plenum.
you can hose clamp those.
injector seals.
intake manifold gaskets/seals.
(to do the last one you have to get the intakes off).

finally a smoke test.

after that once its leak tight.
and its still doing some hesitation its got to be to do with the TPS.
it could still be playing a part.

another place to look for leaks is the throttle body itself.
the bushings on the throttle plate pivot axle.
not much you can do about that without a full rebuild.

as a question.
this 800 rpm you got it down too.
did you adjust the idle screw.
if so. how far down.
is it still off the bottom or have you screwed it down shut.
i'm remembering early on this the idle screw was closed entirely.
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wonkipop
post Mar 24 2023, 12:12 AM
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further question.
when you say it would start immediately.
this was with the AAV shut off completely and the decel vavle isolated and closed off?


i can tell you this system is entirely intolerant of any air leak.
after i recommissioned mine the throttle body gasket gave up the ghost.
it was half a century old.
i was quite astonished by the degree of unstable idle and inability to idle from this tiny air leak. new gasket kindly supplied by an aussie site member and away i went.
problem gone.

as you close off the obvious sources of additional air its going to go find the other ones that are there and are available for it to suck air through. it induces them in fact. which might explain why its all over the place a little bit. its looking for air leaks. the more you tighten it up the more it wants to find whats weak. same as capilliary water leaks into buildings.

anyway, there are still some air leaks there to find in yours.
but you are getting closer on that front.
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tshih914
post Mar 24 2023, 03:46 AM
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QUOTE(wonkipop @ Mar 23 2023, 10:12 PM) *

further question.
when you say it would start immediately.
this was with the AAV shut off completely and the decel vavle isolated and closed off?


i can tell you this system is entirely intolerant of any air leak.
after i recommissioned mine the throttle body gasket gave up the ghost.
it was half a century old.
i was quite astonished by the degree of unstable idle and inability to idle from this tiny air leak. new gasket kindly supplied by an aussie site member and away i went.
problem gone.

as you close off the obvious sources of additional air its going to go find the other ones that are there and are available for it to suck air through. it induces them in fact. which might explain why its all over the place a little bit. its looking for air leaks. the more you tighten it up the more it wants to find whats weak. same as capilliary water leaks into buildings.

anyway, there are still some air leaks there to find in yours.
but you are getting closer on that front.


@wonkipop
The engine indeed needs a full tune up and new spark plugs and probably a new CHT sensor replacement as well as all the other old seals that you mentioned as potential sources of air leaks.

To get the 800 rpm idle I had to adjust the idle adjustment screw 2.5 turns off bottom position. AAV blocked off and decel valve rear and side hoses blocked.

The throttle body seal is newly replaced when I was checking the throttle switch and terminal. Thanks to you and Mike we are making tremendous progress. Greatly appreciate the methodical troubleshooting approach being applied to this problem.

A question regarding the throttle body mechanism : what is the role of the upper part which consisted of a concentric lever that is connected to a spring off the back wall of the engine bay?
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wonkipop
post Mar 24 2023, 04:35 AM
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QUOTE(tshih914 @ Mar 24 2023, 03:46 AM) *

QUOTE(wonkipop @ Mar 23 2023, 10:12 PM) *

further question.
when you say it would start immediately.
this was with the AAV shut off completely and the decel vavle isolated and closed off?


i can tell you this system is entirely intolerant of any air leak.
after i recommissioned mine the throttle body gasket gave up the ghost.
it was half a century old.
i was quite astonished by the degree of unstable idle and inability to idle from this tiny air leak. new gasket kindly supplied by an aussie site member and away i went.
problem gone.

as you close off the obvious sources of additional air its going to go find the other ones that are there and are available for it to suck air through. it induces them in fact. which might explain why its all over the place a little bit. its looking for air leaks. the more you tighten it up the more it wants to find whats weak. same as capilliary water leaks into buildings.

anyway, there are still some air leaks there to find in yours.
but you are getting closer on that front.


@wonkipop
The engine indeed needs a full tune up and new spark plugs and probably a new CHT sensor replacement as well as all the other old seals that you mentioned as potential sources of air leaks.

To get the 800 rpm idle I had to adjust the idle adjustment screw 2.5 turns off bottom position. AAV blocked off and decel valve rear and side hoses blocked.

The throttle body seal is newly replaced when I was checking the throttle switch and terminal. Thanks to you and Mike we are making tremendous progress. Greatly appreciate the methodical troubleshooting approach being applied to this problem.

A question regarding the throttle body mechanism : what is the role of the upper part which consisted of a concentric lever that is connected to a spring off the back wall of the engine bay?


if your accelerator cable fails or the throttle spring itself fails (the one coiled on the mechanism) it pulls the throttle closed.
throttle safety spring.
it all goes in the opposite direction with the rear engine VW engines. you will notice there is a little hole in the seam of the air distributor plenum on the upper seam. thats for hooking the spring into on the rear engine VW applications of the same engine.

i watched your film a second time.
you managed to actually match the AFM flap to available air there at the point where you got it to 2000 approx rpm. it actually sounded alright. sounded smooth! you were there. was it sweet for a moment?
its a video and not really the same as being there, but for a moment it sounded sweet. like you were the human intervening in the out of sorts infant proto electric "intelligence" that was very upset and having a tantram, and you kind of fooled it into something close to the correct air fuel mix. which was the idea of the test. glad you could be persistent and have a go at it. its easier using your fingers with the air cleaner off and not a screw driver. i've watched mike do the same thing with an AFM on a 964. he diagnosed a bent flap on that along with some other issues, so i knew what he was talking about when he instructed me to tell you to do this procedure. the 964s have the same fragile AFM flapper as the old 914s!!! not that there is necessarily anything wrong with your AFM. he did do it with mine when he was fooling around really tuning it up at one stage.
i just let him do it. but he was playing with the AFM flap. that was a few years back when we were bringing it back to life. its an olds hands trick. some of the guys here would probably know how to really do it. its all part of playing with it when you are timing the car and tuning it up. (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/drooley.gif)

according to him the air leak saga goes on forever. you plug one and then the greedy engine goes looking for the next faded jaded connection and just blows her open. or sucks it open to be technically correct. you do get to the end of it. you can pre-empt it by simply doing them all to start with as others here have suggested. despite you plugging off AFM and AAV real tight i think now its finding the other weak links. so you will have to chase it all down. its an old girl. she is half a century old. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)

i didn't have any of these problems on raising mine from its coma as i just went right through it before the attempted start and renewed every hose and tested every component amongst a lot of other things. but the throttle body gasket i walked right past and it turned around and bit me. (IMG:style_emoticons/default/biggrin.gif) it just went after the one thing i had not renewed and chewed it up and spat it out.
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wonkipop
post Mar 24 2023, 05:18 AM
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there is one more spot where 1.8s can leak air.
the valve cover gaskets. (or rocker covers as some folks call them).

we glued the gaskets on to the rocker covers with something mild.
i'll ask mike what he used. its an old trick.
its not an aggressive adhesive. i can't remember what it was.
it was his trick. i never had to do it on my old squareback as it was not fuel injected.

if it was leaking air there it would probably be leaking oil from there as well.
although an oil leak there can be confused with a push rod tube o-ring seal leaking.
which they can also leak air through. but there is going to be a bit of an oil leak involved to spot that. puddles on the floor. lots of oil smoke burning off the heat exchangers.
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Geezer914
post Mar 24 2023, 05:55 AM
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I second Wonkipop suggestions. I have left 2 posts telling you to do a smoke test. Stop beating your head against a wall (IMG:style_emoticons/default/headbang.gif) and do it. Ljet high idle is vacuum leaks! Check the large tube from the AFM to the throttle body for cracks.
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nihil44
post Mar 24 2023, 06:47 AM
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Please re visit post #75. I have spent 8 months or so chasing vacuum leaks and I offered my experience of the journey in a spirit of community in the hope that it will put you in the fast lane with this operation.

Please re visit the post. I hope the information will help. Some effort goes into making posts of this nature (photos, re sizing photos etc).

My favoured method/s would be pressure testing with soapy solution or bubble mixture as recommended by the factory or using the same technique except applying vacuum.

Good luck and I hope you some level of satisfaction when you expel the evil spirit of vacuum leaks
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wonkipop
post Mar 24 2023, 05:22 PM
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@tshih914

you were asking about rest position of AFM thousands of pages back.

Attached Image


yep thats how it should be.
(or we are both stuffed (IMG:style_emoticons/default/biggrin.gif))
note the orange 3 bond sealant.
the work of my old german mechanic from must be 30 years ago.
still holding up.
he was fanatical about ze hair leekz in ze luft-troneek as he used to call it. (IMG:style_emoticons/default/biggrin.gif)

Attached Image


and the other end since i had it out.

Attached Image
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wonkipop
post Mar 24 2023, 05:32 PM
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@nihil44 .

i have a feeling he will be looking up post #75. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)


hows your rig going. you got to the bottom of ze hair leekz yet? (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)
ze joyz of zee first space hage teknologee az ze components get older zan ze pyramids.

bet you the current generation of cars don't get as far as the old 914s before all that plastic adorning the engines shizers itself.
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tshih914
post Mar 24 2023, 06:01 PM
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QUOTE(nihil44 @ Mar 24 2023, 04:47 AM) *

Please re visit post #75. I have spent 8 months or so chasing vacuum leaks and I offered my experience of the journey in a spirit of community in the hope that it will put you in the fast lane with this operation.

Please re visit the post. I hope the information will help. Some effort goes into making posts of this nature (photos, re sizing photos etc).

My favoured method/s would be pressure testing with soapy solution or bubble mixture as recommended by the factory or using the same technique except applying vacuum.

Good luck and I hope you some level of satisfaction when you expel the evil spirit of vacuum leaks

@nihil44

I will certainly try your ingenious method of post #75 after I refresh all the old connection seals and valve cover gaskets and fuel injector seals etc and will use compress air via schroeder tire stem valve and soap solution to find any leaks.
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nihil44
post Mar 24 2023, 07:18 PM
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@wonkipop

Was supposed to do a track day 2 das ago but shift link bushing at firewall coupling disintegrated on the way. Bit of a long story but I assumed that the bushing I installed was a Delrin one, mainly by the colour but it was made of some soft crappy material which failed in the most bizarre way.

Car is now running well overall but still pursuing a stumbling issue. I am satisfied the vacuum leaks have been dealt with. The most surprising one was the failed inlet manifold gaskets. That is why I posted urging @tshih914 to re visit my post on vacuum leak testing. It was a long journey for me and I hoped that my R & D would put him in the express lane.
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Porschef
post Apr 1 2023, 08:05 AM
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QUOTE(Geezer914 @ Mar 24 2023, 06:55 AM) *

I second Wonkipop suggestions. I have left 2 posts telling you to do a smoke test. Stop beating your head against a wall (IMG:style_emoticons/default/headbang.gif) and do it. Ljet high idle is vacuum leaks! Check the large tube from the AFM to the throttle body for cracks.


I’ve not read through this entire thread but I totally agree with the smoke test suggestion; it’s very easy with a machine and will immediately point out air leaks. I had a couple, one was at an exhaust flange.

However, Ljet vacuum leaks do not create a high idle condition, it’s quite the opposite. (Djet will) I’m running Ljet on a 2056, 9550 cam and a 123 distributor. Until I eliminated all vacuum leaks it wouldn’t idle properly, and there’s a multitude of places for that to happen.

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tshih914
post Apr 1 2023, 08:07 PM
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Sorry for the lack of progress, lot's of things coming up like tax filings and other priorities in life also start of track driving season. Today I went to Lowe's and got some plastic pipe fittings (2 inch diameter) to make into the tool that improves on nihil44's design. Posted a short video testing the tool on the old gaskets and seals. This is shown on my pfan12000 youTube channel. I still haven't the time to change out all the seals and sparkplugs and fuel injectors seals before final check for leaks. Attached Image
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tshih914
post Apr 1 2023, 08:09 PM
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Attached tire valve stem.Attached Image
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tshih914
post Apr 1 2023, 08:20 PM
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QUOTE(tshih914 @ Apr 1 2023, 06:09 PM) *

Attached tire valve stem.Attached Image

My youTube short video shows minor leaks at the intake runner seals and at the idle adjustment screw at the base of the throttle (expected). Will need help from another person to check again after new seals are installed.
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nihil44
post Apr 1 2023, 11:41 PM
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@tshih914



Pleased you got a result.
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