‘74 1.8L L-Jetronic Cold Start Low Idle, Mystery solved! Options

[wonkipop]

yes @emerygt350 , that would all work to duplicate.

what i will probably do at xmas is just unbolt the aav anyway and do the hose tests etc where i can manouvre the aav. i'll be giving it a good go over again to just see if i can make any difference.

i think you can still get new ones. they put the same AAV on 924s.
i can remember researching it and i seem to recall that i managed to source them.
those aavs that went on L jets went on to be used on a lot of other cars for quite a long period afterwards.

[StarBear]

yes @emerygt350 , that would all work to duplicate.

what i will probably do at xmas is just unbolt the aav anyway and do the hose tests etc where i can manouvre the aav. i'll be giving it a good go over again to just see if i can make any difference.

i think you can still get new ones. they put the same AAV on 924s.
i can remember researching it and i seem to recall that i managed to source them.
those aavs that went on L jets went on to be used on a lot of other cars for quite a long period afterwards.

That info ( part numbers and such) would be a grand resource! New or even good used AARs not seen in 20 years!

[StarBear]

yes @emerygt350 , that would all work to duplicate.

what i will probably do at xmas is just unbolt the aav anyway and do the hose tests etc where i can manouvre the aav. i'll be giving it a good go over again to just see if i can make any difference.

i think you can still get new ones. they put the same AAV on 924s.
i can remember researching it and i seem to recall that i managed to source them.
those aavs that went on L jets went on to be used on a lot of other cars for quite a long period afterwards.

My mechanic found a Volvo hose bend that fit perfectly. Pre-bent so doesn’t pinch.
That alt test is much easier, for sure.

[wonkipop]

yes @emerygt350 , that would all work to duplicate.

what i will probably do at xmas is just unbolt the aav anyway and do the hose tests etc where i can manouvre the aav. i'll be giving it a good go over again to just see if i can make any difference.

i think you can still get new ones. they put the same AAV on 924s.
i can remember researching it and i seem to recall that i managed to source them.
those aavs that went on L jets went on to be used on a lot of other cars for quite a long period afterwards.

That info ( part numbers and such) would be a grand resource! New or even good used AARs not seen in 20 years!

i'll dig back into my files from then and see if i can find it.
i have a feeling i might have sourced it from VW classic germany.
or something like that. someone had them was what i can remember.
the AAV went on a number of VW injected water cooled engines post the 914 L jets.

[Van B]

Trouble with this little project is a I get like one cold start a day lol. Now that I’ve got the decel valve sorted, I’m gonna pull that hose prior to start tomorrow.
I’m definitely not going to bet against emery, but I’m not convinced since I already took the AAR off, cleaned, and did a function check.

[emerygt350]

Trouble with this little project is a I get like one cold start a day lol. Now that I’ve got the decel valve sorted, I’m gonna pull that hose prior to start tomorrow.
I’m definitely not going to bet against emery, but I’m not convinced since I already took the AAR off, cleaned, and did a function check.

It's just a step... Best move would be to pull it while it is running but pulling it first should be good enough. Just be prepared to plug the plenum.
That aar probably reduces the leak size a hair. When I was working on my pcv it would really race if pulled. Not the best thing to do to this engine with cold oil.

[Van B]

Hello all,
I figured this was worth adding to the conversation even though I don’t yet know if it will result in anything toward achieving the cold start high idle.
Last night Wonkipop and I were messaging and he sent me a thread post by legend Capt Krusty. Which I then cross referenced with the manual, also provided by Wonkipop; thank you kind Sir!

http://www.914world.com/bbs2/index.php?sho...p;#entry1170393

This morning I came out to try some cold start stuff and to my surprise, the car wouldn’t start. I thought about it and the only thing I did after the whole spark plug fiasco was make an 1/8th turn in on the air screw after a 20min drive.
The way it went down this morning is that I pulled the retard line from the distributor and left it open while capping the end at the throttle body. Car wouldn’t even try to start so I said, “guess that didn’t work” and put it all back together. However, when I tried again, the car still wouldn’t start. I got it going by adding 25-50% throttle and it stumbled to life. I left it running until it came up to temp and by that point everything was fine.
Then I pulled the retard line and idle came up… but I don’t want that when it’s warm! I spent the whole other thread figuring out how to fix that lol!

Soooo, I put my two brain cells two work and came up with the theory that the plugs have affected timing. Or more specifically, having incorrect plugs not installed correctly, required some messed up timing. I drove the car around a bit today here and there and noticed that even on hot starts, throttle was required to get it to kick over… which wasn’t an issue before.
Which brings me to right now. I bought a timing light, set it to zero advance and followed the procedure in the manual, with the added details from Krusty i.e. plugging the distributor ports and NOT leaving them open. Yeah, timing was off a fair bit. Took about an inch of clockwise rotation in total with a few trips back to the air screw to keep the car from dropping so low it would die. In the end I was able to set 800rpm and get the red line centered. Then I reconnected and adjusted the air screw to get 850rpm for idle. That step is thanks to Krusty.
I’m now waiting on the car to cool completely before I try starting again and see what/if anything changes.

Van

[wonkipop]

good stuff.

the late cap'n krusty had red hot tips.
often i just do a search here to find his methods.



i found some other stuff from the cap'n re the endless discussions about dist vac hookups on 914 1.8s.

the cap'n was firm in his view that all 1.8s came with the two vac hose hook up.
one to advance side of dist vac box and one to retard side.

he also had the best simplest explanation for how it works (the retard side at idle that is).

attached is the screen grab.




--------

but i also did some searching around in the factory manual.
and maybe got to the bottom of it.

lists two different distributors for 1.8
i definitely have the one underlined and its definitely a two port/two hose connection.
which i have still intact and original. so its never been altered and is still the way the factory says it should be (and the way the cap'n said it should be).




another page on manual.
casts light on 75s.
they have the single port (retard only) distributor.
and if the pollution gear is still hooked up on a 75, the port that faces to the rear of the throttle body and is hooked up to vac advance on distributor of a 74, is hooked up to the EGR valve on the 75.




there is a good section in the factory manual with a cross section and explanation of the vacuum advance/retard distributor.
its worth a read if you want to get your head around it.
i won't try it ends up being a complicated discussion if past threads i have discovered are anything to go by.

suffice to say at idle, only the retard line is working because the other port is closed off by the throttle plate. so only the smaller back section of the vac can is activated. retarding the timing. cap'n krusty explains how snapping the throttle open to take off instantly de-retards the timing at that point and you get a smooth take off.

and when the throttle is part open at cruise both ports work off a vacuum.
but the advance port operates a bigger vacuum chamber which overcomes the smaller vacuum chamber (called the retard). net effect of both working against each other is the bigger chamber advances the whole unit under vacuum.

there is other stuff going on of course, but thats the distributor under influence of mechanical weights. the vacuum bits are really working at idle and at part throttle cruise to do two things. lower emissions at idle and to increase fuel economy at cruise.
very 1970s. fuel crisis/pollution crisis.

[Van B]

I read those pages earlier today and successfully didn’t get my head around it!
Bottom line for the tests conducted today. Both vacuum lines are staying connected. Good that what you’ve found confirms that stance.

Also, just tried a cold start and I’m right back to where I was before the spark plugs. I’d be really annoyed right now, if it wasn’t for the fact that the car is running so much better! I’m inching ever closer to getting all 76 ponies back in action! Getting plugs that seat properly made a noticeable difference and then retiming added a little more.
I mean it’s all good right? But as far as low idle on cold start, I’m right back to where I was after solving the high idle mystery.

Oh, one other thing. I used my fancy new timing light to get an empirical rpm measurement. When it starts I get a 700rpm idle. As it warms up, it climbs to the 850rpm I have set. It takes about two minutes to increase that 150rpm.
I’m aware that this is an inference, but 2min is how long it took the AAR to close when I bench tested it a few weeks ago.

Ugh, I hate being dumber than the mid-70’s!

[Van B]

Found this on the YouTubes:

https://www.youtube.com/watch?v=FGEvf16nNQM


This is exactly what my car is like on cold start.

Continuing with the inference of my previous post, is there ANYONE with a 1.8L that actually gets a high idle from their car when starting from cold?
https://youtu.be/FGEvf16nNQM

[wonkipop]

I read those pages earlier today and successfully didn’t get my head around it!
Bottom line for the tests conducted today. Both vacuum lines are staying connected. Good that what you’ve found confirms that stance.

Also, just tried a cold start and I’m right back to where I was before the spark plugs. I’d be really annoyed right now, if it wasn’t for the fact that the car is running so much better! I’m inching ever closer to getting all 76 ponies back in action! Getting plugs that seat properly made a noticeable difference and then retiming added a little more.
I mean it’s all good right? But as far as low idle on cold start, I’m right back to where I was after solving the high idle mystery.

Oh, one other thing. I used my fancy new timing light to get an empirical rpm measurement. When it starts I get a 700rpm idle. As it warms up, it climbs to the 850rpm I have set. It takes about two minutes to increase that 150rpm.
I’m aware that this is an inference, but 2min is how long it took the AAR to close when I bench tested it a few weeks ago.

Ugh, I hate being dumber than the mid-70’s!

thats pretty close to how mine behaves on the cold start Van.
mine might even be a little weaker than that for the first 30 seconds/1 minute or so.

i should time it this weekend when i cold start.
will give you a comparison time for mine before it stabilises at its set warm idle around 850.

we will probably crack it eventually.
i'm trying to find that info i tracked down on aux air regulators/valves.
i know its the same as the one put into 924s and 944s.
but that doesn't get you any better off as its NLA for those cars too.
but there are a lot of very similar AAVs that ought to bolt straight in.
the only difference between them all is the rate at which they close and the size of the opening passage when cold.


only other thought i have is the electrical connection (wire) to the CHT.
you have a new CHT and got no difference.
i tested my CHT and it was ok.
but maybe the connection back to the ECU.
i'd have to look that up how to test at the other end.
have you done it?

[StarBear]

Found this on the YouTubes:

https://www.youtube.com/watch?v=FGEvf16nNQM


This is exactly what my car is like on cold start.

Continuing with the inference of my previous post, is there ANYONE with a 1.8L that actually gets a high idle from their car when starting from cold?
https://youtu.be/FGEvf16nNQM

Nope, but I like to set my idle a bit higher, at 950-1000 rpm so that might be masking it. Sealed up the connection downstream from the AAR to the air box as I couldn’t get a leak free seal. Two wraps of black electrical tape.
This is a much- needed thread. Destined to be a classic for 2-port 1.8L cars.

[wonkipop]

@Van B & @StarBear .

full cold start test this morning for you.
car hasn't been started for a week so fuel system has bled down to lowest pressure.

temp = 13C (55-56F).
yep its a miserable spring day in melbourne.
arctic roaring 40s cold front coming through.

no touch nothing. car on its own.

two cranks. err err bam fires.

5-6 seconds strong start at 1000 rpm.
(i figure thats the cold start injector working - so much for 50 and below).

then idle drops to bottom of tach. don't even know if its making 750 rpm.
doesn't sound like it. but its keeping itself going steady.
this lasts for 2 minutes.

at 2 minute to 3 minute mark is the interesting bit.
this is the weakest phase.
it stumbles, barely keeps itself going but L jet just won't let it die.
comes back, stumbles again comes back, does this 3 times.

at 3 minute mark it begins getting stronger. but still not there to set idle.
stops stumbling. gets even at 800 rpm.

up to 4 minute mark stays at even 800 rpm.
can feel warm air puffing out from underneath at my ankles.

at 5 minute mark hits even 850 rpm and is strong and steady.

at 6 minute mark it hits the idle we set it to back at last service which was 950 rpm.
like StarBear we found it sat there nice and even last time we tuned it so that is where we have it.

its a full 6 minutes.

-----

i did not do the emorygt test of pulling hose off decel valve line.
like you only get one full cold chance a day (more like a week really have to shift other french things out of the way).

awful weather coming in down here.
so i probably won't get a chance for a drive today. (IMG:style_emoticons/default/sad.gif)
but i'll let it sit while i potter about doing some other stuff and try a "cool" start later to see what it does after you leave it for most of the day.

[emerygt350]

You have to do the aar tests. They cost nothing and until you do I think next steps are really hard to guess. A low idle is always retarded timing and or a rich mix on a fuel injected engine. The aar is really key for that craptastic half warm period on these engines.

[wonkipop]

i just did a cool start.
its about 4.5 hours later.

i get about 1 minute of slightly wobbly idle around the 800-850 mark.
then its settles at 850 for about another minute and rises to 950 steady.

@emerygt350 - yeah, i've always had a strong suspicion its the AAV when it comes to mine.

i know it works or it worked and i think it still does based on this morning. but not like its meant to new. i fully cleaned and tested it 2 years ago.
i'm pretty sure it closed from fridge cold in about 2 minutes. somewhere in my notes i wrote it down.

stone cold test start that i bothered to actually time this morning seems to point to AAV working for 2 minutes. the first 2 minutes it was running steady but at a very low idle.

then went into a strange phase for minute 2 to minute 3 - thats telling me something.
i think it wanted air but couldn't get it.

a few posts back i speculated my AAV is closing too fast.
its a wonder the one i have has lasted as long as it has.
being laid up for 15 years probably helped it get to here.

i'm not going to do your hose pull test on the decel valve.

i'm going to do a different one when i get time out at the shop when i take the car there for some other things i want to do.
i will unbolt the AAV then but leave it plumbed up and do a start where i just pull that hose off and test it all that way. also i think there is an AAV lying around off another porsche and one off something else out at the shop i can rig into the plumbing just to see what different aavs do at start up. do all my tests at same time.

i can't find anything in manuals that tell us how long the AAV is meant to take from full open to full closed. but from what i did this morning i believe it should be something around the 5 minute mark? if i can find enough AAVs lying around that i can sub in i might come up with something more than is it just not working at all.

[wonkipop]

i also have just had one other thought for Van B.

i don't know why i did not think of it earlier.
probably because i never think of it.

the thermostat and cooling duct flaps for fast warm up.

i don't have them hooked up.
maybe he doesn't either?

you plain don't need that heath robinson contraption in australia.
everybody has always unhooked them on all VWs in australia since the year dot.
i know there are purists who say the opposite (but we don't live in antarctica here).
despite what the purists say they can jam in the close position.
its rare for a thermo to fail that way but its not unheard of or wasn't unheard of in the old days. if it does it will hold the flaps shut and.........

mine have been unhooked for 30 odd years.
but i have only been having the weaker start up since recommission and a little more weaker gradually more recently.

i think my AAV was always up to the job for the first 15 years back in aus in the 90s.
but now its weaker. now it can barely cope without those fast warm up flaps as well?

its a thought.

Van B will have to sniff around his thermo stat under the car and see if the flaps are all still connected to it and what state the thermo itself is in.
that might help him get his desired factory fast warm up he is after.

given the number of crappy chinese products around these days i'd be looking real hard at any thermo i bought to make sure it was the real deal and up to it.

[Van B]

Lots of science going on down under today lol!
My car has a similar pattern but no stumbles.

Here’s what I’ve concluded:
- My CSV aka 5th injector only works while cranking the engine
— This is where the initial gusto on startup comes from

-2min is the average time for the heating element to close the AAR from 15C
— This is the same time my car spends at 700rpm before it starts to climb

- Even a slight vacuum leak on the manifold will negatively impact idle
— Vacuum advance is essentially inoperative at idle but retard is directly impacted via air screw
— I had to re-time again today as I found that the short tube from AAR to manifold wasn’t sealing completely
—- changed the tube and timing was off by 1 degree
—- Since the procedure on our car requires air screw adjustment prior to timing, you must retime whenever you do work that affects manifold pressure


Now, about the AAR, I’m 100% mine is fully functional. I can’t say it works as well as it should or could, but it’s working. Also, and most confusing, when it starts to close, is when the car starts to pick up rpm. Too much air and too little fuel? Should the CSV continue to add fuel after start up?
These are the things I’m wondering right now.

Van

[Van B]

Forgot to attach this:

[wonkipop]

(IMG:style_emoticons/default/smile.gif)

re timing.
thats why i am leaving all this alone until a week at the workshop.
i know what you mean. had to thrash around with the disributor and the timing light over a leaky throttle body gasket last year.

i think i'm running tight on the air leaks front.
we buttoned all that up good a while back and smoke tested carby spray etc.

i decided to get less anecdotal today and watch what it was doing empirically against the clock instead of just what i thought i could recall.

i found minute 2 to 3 interesting and i'll talk to my mechanic tomorrow when i am out at the shop torturing myself on the falcon. i'll bet he has his usual line - "AAV"
to him thats saying the engine warming up is out of phase with the AAV closing down.
but we will test everything all over again including i think sensor ! in the AFM unit.
may as well.

its only the warm up from stone cold that is a little unusual.
the thing runs beautifully once its warm.

i am a bit inspired by your determination to get to the bottom of it and just do it.

(IMG:style_emoticons/default/beerchug.gif)

re the CSV after start up.
my view is it does until the thermo switch turns it off.
which might be fairly quick if things are above 50F.
its basically kind of like the AAV.
its thermoswitch is heated by a current.

if i understand it right its going to work from 50 to 68F according to my L jet manual.
the thermo might take say 4 seconds to heat from 50 to 68 and cut off.
2 seconds from 60 to 64 or whatever.

and when its below 50 it takes what it takes to get to 50 and then from there to 68.
with a proviso that no matter what it is max 20 seconds. (thats the factory man test) - otherwise you are flooded.
if it goes for 20 seconds say, its probably arctic conditions like chicago in mid winter.
nothing like that would happen in australia unless you were up at ski resort.

normally its just a quick splash of fuel like a gas pedal pump?
and its not part of warm up beyond that?
given at most it can only last for 20 seconds when its really really cold.
but thats another thing i will go through at xmas with the manual and the thermoswitch.
the only difficult is that xmas in australia is summer and its usually really hot here.

[Van B]

That makes sense to me. That injector definitely puts out a lot of fuel. And the fact that it's constant on while cranking puts the engine at risk of flooding. I could smell raw fuel pretty strong the day my car didn't want to start.

I'm still trying to understand the dynamics at play here from the L-jet point of view. Generally a choke phase would enrich the air fuel ratio. Maybe I'm begging the question here, but why does the idle speed improve after the AAR is closed?

I'll be out of state all week again, but when I get back, I want to pinch off the AAR and see what happens on a cold start.