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

[Van B]

Ok fellas, here’s the run down Aux Air Regulator (AAR) and Cold Start Valve (CSV)/injector both work fine. Many of you have also been keeping up with my high idle issue that we figured out.

But yet, when the car is cold, i.e. room temp, I don’t get the high idle I should on start-up. Instead she cranks a bit and then lumbers to life. Idle lopes around 700-800rpm and then smooths out as it warms.

In all other aspects of operation, the engine seems to be pretty happy.

Thoughts? Experience? (IMG:style_emoticons/default/confused24.gif)

-Van

See post #419 on page 14 for a synopsis of the outcome.

[emerygt350]

Just checked my 009. Full retard is 7inhg so the aar wouldnt affect that from triggering. Idle even with the aar is >17 on my djet, probably close to that on an ljet.

[emerygt350]

Just checked my 009. Full retard is 7inhg so the aar wouldnt affect that from triggering. Idle even with the aar is >17 on my djet, probably close to that on an ljet.

The more I think about that 7 the more it makes me wonder... I pull a 7 pretty much all the time unless I am accelerating or climbing. Can the vacuum be so much different in the throttle body? Must be...

[wonkipop]

That's right wonki. Bypassing the AFM will throw off the whole fueling equation. It opens more variables than it eliminates. Popping the line to the AAR to check for air draw is feasible once the car is running. But I'm opting for pinching the short line in order to keep everything else accounted for. If pinching that line during cold start makes the condition worse, then to me it makes a strong case that the AAR is not meeting air flow requirements. Conversely, you could say that the engine is being over fueled, but given the objective of higher RPM than normal for engine warm up, such a statement doesn't make sense.

So, I start the car and then pinch the line:
1. RPM increases
2. RPM decreases
3. RPM remains the same

If #1 happens, then it's a lean condition I'm suffering from during warm up. If #2 happens, then it's a rich condition. If #3 happens, then the AAR is already closed.

What am I missing?

Alright, I’m back home today and this morning it was a chilly 4C. So, I was able to give it a proper cold start and do my little test.

First, I started the car as normal and then jumped out and pinched the short line from the AAR to the manifold. To my surprise I only got a subtle 100-ish RPM drop. I unclamped and reclaimed just to be sure, but yeah, that’s all I got.
Also, the car started no different today at 4C than it does at 15C. I thought that was interesting too.

Second, just for S’s and G’s I pulled the line from the boot to the AAR and the car died instantly. And I mean the instant I disconnected that hose. I had no time to even put my thumb over the ends. So, as predicted that is a lost cause.

Lastly, I moved the adjustment pin on the AAR all the way to the outside but got no change. I didn’t expect much really given how cold it is. I’m pretty sure the AAR is as open as it can be.

My thoughts so far:
I’m confident that everything is in fact functioning, but if I want to get the idle higher, I’m going to need more air flowing through the AAR channel during warm up.
Which means, I’m at a dead end for now.

Van

@wonkipop
That theory reconciles with this test. Also, when I ran a tube from the intake boot to the manifold, bypassing the AAV, the idle climbed way high, almost runaway even on cold start.

i'm definitely going to chase up one of those summit racing AAVs.

when i get it i will pull the one out of the 914 and sit them side by side and run current through and compare them.

[Van B]

If you look at the bottom of the summit link I sent, you’ll see that there are two that use the standard Bosch plug, not sure what the difference is between them. The rest are a modified Bosch plug with the ridge offset to the side. Those all seem to go on post-Datsun Nissan cars.

[Van B]

Just checked my 009. Full retard is 7inhg so the aar wouldnt affect that from triggering. Idle even with the aar is >17 on my djet, probably close to that on an ljet.

The more I think about that 7 the more it makes me wonder... I pull a 7 pretty much all the time unless I am accelerating or climbing. Can the vacuum be so much different in the throttle body? Must be...

I don’t know Bernoulli, but he probably has something to say on the matter lol…

[StarBear]

[/quote]

i'm definitely going to chase up one of those summit racing AAVs.

when i get it i will pull the one out of the 914 and sit them side by side and run current through and compare them.
[/quote]
Please do let us know! That could be a valuable Plan B. Mine is working fine (I think) but it is almost 50 years old.

[Rob-O]

Yeah so, little to no vacuum while cranking, then on kick over, engine vacuum pulls the retard.

Not sure what this means, but if I pull the oil cap with the car running, it instantly dies. So vacuum abounds I suppose.

F**k it, I’ll vacuum test everything I can get the mighty vac on this weekend lol

its all sealed.

another area you can get problems from in L jet is the valve cover gaskets.
but you would know if that was an issue. there would be oil leaks.
but the L jet does need to be buttoned up tight.

how are the gaskets in the oil cap. in good condition?

the AFM can't measure an air leak as big as the oil cap off which is leaking air straight into the hose from the AFM to the TB.

i guess the valve covers mean it can leak air via the crank case up into the PCV and from there into the same hose.

doesn't like false air from anywhere that the AFM can't measure.

i had a leaky throttle body gasket that seemed to kick in when the engine got hot.
thermal expansion. started fine. drove ok for 10 minutes, then went haywire.
i could keep it running but it would die at the lights. replaced the TB gasket with a new one from 914 rubber. problem went away. the old gasket had just gone hard.
surprised me how it managed to leak.

Okay, slow down here guys. Again you’re throwing out so much information there is no way anything substantive can get done.

One…thing…at…a…time.

But for the above…I’m going to disagree with you on valve cover gasket leaks. L-Jet doesn’t have head venting, doesn’t have a PCV and as such I can’t see a path where a leaky valve cover gasket is going to introduce an air leak. But I CAN SEE how the information dump would get Van losing focus on what he’s checking.

The last I saw was that parts in the distributor were gummed up. But that’s it. Are they now ungummed? Are the points adjusted? Is the cap and rotor in good condition? Are the advance plates moving freely? The advance plates are HUGE to proper operation of the distributor.

You mentioned that the distributor moves. Do you mean the whole body of the distributor? Because I can’t see how you can move forward investigating anything else if the distributor body is possibly moving. There are two nuts that hold the distributor in place. The nut that holds the distributor clamp to the engine case and the long nut that tightens the clamp around the distributor body to prevent it from moving. Test the vacuum canister.

More stuff that we can discuss after the above has been verified.

How the retard and advance works. But right now know that you time the car with vacuum lines disconnected. You time it to 7.5 degrees of advance. Which means that at idle the engine is FIRING the spark plug when the piston is 7.5 degrees BEFORE hitting the top of its stroke. The vacuum ADVANCE canister is just going to pull the advance weights into the ‘flung out’ position quicker than they normally would. But even without the canister…if your advance plates are moving freely…advance is going to happen.

With vacuum retard I don’t believe you’re pulling enough vacuum…at idle…to affect timing. That’s not the design of using a vacuum canister with retard. I believe it is…or was at the time…used to pull the advance plates closed quicker. But again…we can argue all that some other time on a different thread (or do some searching through past threads here and elsewhere). But first? That distributor has to be gone through. Timing has to be set, all ignition items need to be addressed to ensure they’re in proper working order. As I said before, don’t complicate this (or assume that something is working because of a line of thought). Pull the canister from the distributor. All the way off. You said you were sure about disconnecting the arm vacuum canister arm. To find it, remove the dizzy cap. Pull the rotor. Look at where the canister is attached to the side of the dizzy. From inside the dizzy you’ll see a metal arm running from the area of the vacuum canister to a point on the advance plate of the distributor. That small metal arm is connected to a small post and held in place with a small ‘c’ or ‘e’ clip (can’t remember which). Disconnect it (don’t drop it in the distributor!!!!!!!!!!!!!).

I’d also highly suggest a Pertronix igniter. They’re cheap (about $80 on Amazon) and let’s you do away with points and condenser). No more adjusting points and one less thing to worry about.

[Van B]

Thanks Rob.
Distributor was never gummed up. Advances fine and timing is set. My comment about movement is me being less than impressed about the effectiveness of the clamp.
I will check that the canister is leak free this weekend and I’ll pull the cap off and have a look. I’m guessing the cap is what you all call the dizzy?
I still would like you to explain what’s accomplished by removing this clip if you don’t mind?

[wonkipop]

@Van B & @StarBear

quick question for you both.

does either of your cars have a centre console and gauges.

and of course StarBear can tell me whether it had it from the showroom.

(might have cracked these painted tinware numbers).

[wonkipop]

Yeah so, little to no vacuum while cranking, then on kick over, engine vacuum pulls the retard.

Not sure what this means, but if I pull the oil cap with the car running, it instantly dies. So vacuum abounds I suppose.

F**k it, I’ll vacuum test everything I can get the mighty vac on this weekend lol

its all sealed.

another area you can get problems from in L jet is the valve cover gaskets.
but you would know if that was an issue. there would be oil leaks.
but the L jet does need to be buttoned up tight.

how are the gaskets in the oil cap. in good condition?

the AFM can't measure an air leak as big as the oil cap off which is leaking air straight into the hose from the AFM to the TB.

i guess the valve covers mean it can leak air via the crank case up into the PCV and from there into the same hose.

doesn't like false air from anywhere that the AFM can't measure.

i had a leaky throttle body gasket that seemed to kick in when the engine got hot.
thermal expansion. started fine. drove ok for 10 minutes, then went haywire.
i could keep it running but it would die at the lights. replaced the TB gasket with a new one from 914 rubber. problem went away. the old gasket had just gone hard.
surprised me how it managed to leak.

Okay, slow down here guys. Again you’re throwing out so much information there is no way anything substantive can get done.

One…thing…at…a…time.

But for the above…I’m going to disagree with you on valve cover gasket leaks. L-Jet doesn’t have head venting, doesn’t have a PCV and as such I can’t see a path where a leaky valve cover gasket is going to introduce an air leak. But I CAN SEE how the information dump would get Van losing focus on what he’s checking.

The last I saw was that parts in the distributor were gummed up. But that’s it. Are they now ungummed? Are the points adjusted? Is the cap and rotor in good condition? Are the advance plates moving freely? The advance plates are HUGE to proper operation of the distributor.

You mentioned that the distributor moves. Do you mean the whole body of the distributor? Because I can’t see how you can move forward investigating anything else if the distributor body is possibly moving. There are two nuts that hold the distributor in place. The nut that holds the distributor clamp to the engine case and the long nut that tightens the clamp around the distributor body to prevent it from moving. Test the vacuum canister.

More stuff that we can discuss after the above has been verified.

How the retard and advance works. But right now know that you time the car with vacuum lines disconnected. You time it to 7.5 degrees of advance. Which means that at idle the engine is FIRING the spark plug when the piston is 7.5 degrees BEFORE hitting the top of its stroke. The vacuum ADVANCE canister is just going to pull the advance weights into the ‘flung out’ position quicker than they normally would. But even without the canister…if your advance plates are moving freely…advance is going to happen.

With vacuum retard I don’t believe you’re pulling enough vacuum…at idle…to affect timing. That’s not the design of using a vacuum canister with retard. I believe it is…or was at the time…used to pull the advance plates closed quicker. But again…we can argue all that some other time on a different thread (or do some searching through past threads here and elsewhere). But first? That distributor has to be gone through. Timing has to be set, all ignition items need to be addressed to ensure they’re in proper working order. As I said before, don’t complicate this (or assume that something is working because of a line of thought). Pull the canister from the distributor. All the way off. You said you were sure about disconnecting the arm vacuum canister arm. To find it, remove the dizzy cap. Pull the rotor. Look at where the canister is attached to the side of the dizzy. From inside the dizzy you’ll see a metal arm running from the area of the vacuum canister to a point on the advance plate of the distributor. That small metal arm is connected to a small post and held in place with a small ‘c’ or ‘e’ clip (can’t remember which). Disconnect it (don’t drop it in the distributor!!!!!!!!!!!!!).

I’d also highly suggest a Pertronix igniter. They’re cheap (about $80 on Amazon) and let’s you do away with points and condenser). No more adjusting points and one less thing to worry about.

in my case yes to all.
all fully tested 18 months back.
all functioning well. distributor. sensors. vac lines.

its not a thrashed out car i have.

the one thing i cannot measure is the AAV. in my case.
it works. but the question for me is it working right.
i have been able to find out the failure modes.
they either stick and jam up or as they age they weaken and
a) don't open enough at start.
b) then proceed to close too quickly.

thats why i am isolating it down to that.

i don't really have a problem with the way mine runs.
just Van has inspired me to sort out this warm up phase.
it has no other hiccups and runs fricken fantastic after its been going 5 -10 minutes.


i think if folks had a worn out system petronix sounds like a good idea.
i'm out to preserve the set up i have as a functioning museum piece.
......a bit like having a model T in the garage.

agree with your points re how the distributor works.
starts at 7.5 BTDC. vac retard side of distributor pulls it back to about 4 BTDC.
it does that for emissions.
there is no cetrifigal advance or vac advance coming into play at idle.
the ported vac is above the throttle plate and excluded.
and you are right its meant to come off that retard really quickly, the minute you snap open the throttle. because that amount of retard is sh*tty for taking off. so the springs snap it off fast.

its another discussion we could have about the vac advance.

i think i explained how taking the hose off the pcv introduces air into the system.
it wasn't an info dump.
its just all those things have to be tight.
thats another discussion. but the demo is simple.
undo the oil cap and the engine will stop, i've done it myself.
the rocker cover gaskets offer a similar route, probably via the pushrod tubes?
and into the pcv? its a closed system. or its meant to be.
you are correct, its not really a valve in a 1.8. its just a closed loop.

the one principle i stick to with L jet is its measuring air.
and if it can't measure it - it gets in trouble.

(and if for some reason it can't measure fuel to air its in trouble?)

[wonkipop]

[quote name='StarBear' date='Dec 15 2021, 05:27 PM' post='2967219']
[/quote]

i'm definitely going to chase up one of those summit racing AAVs.

when i get it i will pull the one out of the 914 and sit them side by side and run current through and compare them.
[/quote]
Please do let us know! That could be a valuable Plan B. Mine is working fine (I think) but it is almost 50 years old.
[/quote]

yep, we are in the same spot StarBear.
so i will let you know.
50 year old model T.

we will crack it.

[emerygt350]

Dizzy is the whole thing, not just the distributor cap.

[wonkipop]

Dizzy is the whole thing, not just the distributor cap.

(IMG:style_emoticons/default/lol-2.gif)

we just use the cap and throw the rest away in australia.

------

yeah you got to dig down into the dizzy and lubricate the whole thing.
make sure the cam and arm are moving. that the plate is rotating freely etc.

i've done that on mine.
that was how i got my head around what those double can distributors did.
18 months ago i had misconceptions about them.
i don't since then.
there are explanations earlier in this thread and van has posted the cross section several times from the factory manual.

it can get confusing since in truth both sides of distributor do advance and retard,
both mechanically and with vacuum depending on engine revs, load etc.

but that so called retard can is only in effect at idle. its like a separate mechanism of sorts. the best way to describe it is just to study the drawing. better than words.
its limited to about 3-4 degrees of movement.
retards at idle that further 3-4 due to engine vacuum from port below throttle plate.
for emissions.
once throttle is opened, vacuum comes off and spring snaps it forward to 7.5.......
and centrigal advance takes over.

so called vacuum advance can has effects on the other side of that at part throttle cruise situations. it is able to advance the distributor well beyond the situation that the centrigal advance goes to. for fuel economy. it also dampens the way the distributor responds. VW used the vacuum can distributors with an advance can for years before the 914. to help the little 4 cylinder engines drive smoothly at cruise and for fuel economy. whereas during the same period porsche just used mechanical distributors on the 911. they were not that interested in fuel economy or smooth throttle response?

the dual can distributor is quite a neat little device if you still have one that works ok.
trouble is most of them are had it by now.

mine isnt. its got many more miles left in it yet.

hence my interest in the AAV.
i've focussed in on it having eliminated everything else.
and its a fairly esoteric point, since its only about the warm up phase.

i suspect van's problem is similar.
in terms of this particular "complaint".

i'll get around to it once i get hold of a second AAV and will be able to answer the question.

i was right a little while back on a separate issue he had when i suggested it was the decel valve. others were bombarding him with all sorts of stuff.
thats not a boast. it was just that i had a very good sense of what it was he was describing. as a result of that i can now tune up a decel valve i managed to find down here for mine. he gave us the vacuum value. i'd asked about that here before and got precisely zero response about 6 months back. no one knew.

its the same with these AAVs. no one actually knows what the parameters are for one of these things when brand new and properly tuned to the engine they were destined for.

[Van B]

@Van B & @StarBear

quick question for you both.

does either of your cars have a centre console and gauges.

and of course StarBear can tell me whether it had it from the showroom.

(might have cracked these painted tinware numbers).

No console on mine from the factory. I bought some OE gauges from Tom here on the forum and was dead set on installing a console, but now that I’ve gotten used to the open floor, I’m not so sure. I’m wondering about a nice three gauge setup attached to the underside of the dash…

[emerygt350]

Yeah, don't do the console unless you need something to rest your leg on. I like mine, and rest my leg there, but I think the open cab is much more elegant.

[StarBear]

@Van B & @StarBear

quick question for you both.

does either of your cars have a centre console and gauges.

and of course StarBear can tell me whether it had it from the showroom.

(might have cracked these painted tinware numbers).

No console on mine from the factory. I bought some OE gauges from Tom here on the forum and was dead set on installing a console, but now that I’ve gotten used to the open floor, I’m not so sure. I’m wondering about a nice three gauge setup attached to the underside of the dash…

Yep; mine came with Appearance Group so had the console and gauges. Think he has cracked the tin numbers codes though concur with Jeff B that it’s wacky but the data lines up! Makes us 1.8 folks “special”, eh?

[wonkipop]

@Van B & @StarBear

quick question for you both.

does either of your cars have a centre console and gauges.

and of course StarBear can tell me whether it had it from the showroom.

(might have cracked these painted tinware numbers).

No console on mine from the factory. I bought some OE gauges from Tom here on the forum and was dead set on installing a console, but now that I’ve gotten used to the open floor, I’m not so sure. I’m wondering about a nice three gauge setup attached to the underside of the dash…

Yep; mine came with Appearance Group so had the console and gauges. Think he has cracked the tin numbers codes though concur with Jeff B that it’s wacky but the data lines up! Makes us 1.8 folks “special”, eh?

the clue might be that stunning ravenna green car.
thats got a dealer installed console.
at point of sale, not some later bring it in and add it job.
its in the paper work.

check it out. a factory console, but not the gauges. !!!!!
on top of that the temp sensor is not via a taco plate its using the oil temp sensor position on the top of the engine (see weird thing sticking up on a metal tube post).
all of its dealer installed.

i don't know quite what that means exactly. but its showing i guess that sometimes even the dealers could not scrounge together all the parts they needed to get a car off the floor in a way the customer wanted. ie it was not all click your fingers plug and play.

a certain amount of the cars were being built direct in the factory that way.
the console was not necessarily a distributor installed item at the main warehouses in USA or even at the dealers. though they could do it certainly to get a car off the floor the way a customer crunching them wanted it waving cash in front of their noses.

knowing the germans the last thing they would have wanted was the car up on a hoist at karmann factory with a couple of turkeys swapping taco plates over if they could possibly help it. would be better if the engines came off the rack already set up.

i went to the ford factory here once many years ago. that was interesting. the guys on the line had build sheets. they check the parts they are installing before they go in and tick them off. they were using scanners and bar codes by that time.

be interesting to see if VW archive/museum has any production line build sheets from the era on file as artefacts. i'm guessing they would have been retained by karmann.
karmann went broke a few years back and are closed now. hopefully their archive was retained by VW and rehoused?

EDIT

where you get the real picture is some of the stuff stamped all over the back of beetle engines. there can be up to three of these number codes. they used M and then three numbers. so there will be three slightly haphazard stamps there.
in the case of the type 1 engines thats already been worked out by kooks even crazier than me. and its all engine spec apparently. one of them will show what carb is on it.
another whether is a carbon cannister hook up. etc. so instead of just one number to describe what it is, it gets really cuckoo clock and the things cop up to three stamps.

probably by the time they set up the hamburg factory to make type 4 engines some rationalist stepped in and reordered the system to get rid of the austrian accounting methods.

[emerygt350]

Just thought I would post my warm up.
Starting (40F) (no touching the gas pedal)
https://youtu.be/5Nm7N8xJ4P8

2 minutes later
https://youtu.be/IzlGgfP5KEA

After 15 minutes driving around.
https://youtu.be/6q2CMoWxn1c

It took a good 15 minutes for it to finally go off the AAR.

My idle afr looks a little lean but it smells good so I think I might leave it there.

[Van B]

That’s with your manual valve right?
Looks just right!

[emerygt350]

That’s with your manual valve right?
Looks just right!

Yes, with it full on it goes up to 1800 or so after a couple minutes, which I find a little excessive.