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?

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.

@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.
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.

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.

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.

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.

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

Forgot to attach this:

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.



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.

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.

Pull it off the air cleaner and cap it with your thumb. If you can feel it sucking then you know it is working.

Yeah, I can play little dutch boy too. First will be some forceps on the short line. Prior to my first crank over. Then if there's nothing different, I'll do as you described.

Like I said on the last thread, the AAR bench tested successfully. Open, closed, opened again. It was a 70 degree day when I tested it so it wasn't fully open to start.

I'm also still really wanting to hear from someone with a 1.8 L-Jet that gets a proper high idle on cold start... I could be chasing fiction.

Forceps don't give the best seal. Is it hard to reach the air cleaner hose? I have never had the honor of mucking around with a 1.8. I was also just thinking about 1.8 and leaks. That Aar leak is pretty big and the computer? Or something must compensate for that particular, momentary, leak. If it isn't there or not what it is expecting the outcome could be pretty unpredictable. Not like the 2.0 at all.

All great stuff, mates! My flaps are on and working. Real thermos are available though pricey. I think I have the source (US) if needed; common to many VWs but there are two different versions.
35 F here this morning. Might try a very cold start and report.

I'm using the forceps to see if the engine wants a richer mixture on cold start. If the forceps result in a higher cold start rpm, then my working theory will be that the engine is too lean on cold start. If the engine struggles even more with forceps on, then the AAR is not providing enough air.

We'll see... It could also result in not a damn thing lol....

Here's my Virgo Engineer testing this AM:
Tuneup 2 days ago. 49 degrees dwell; 7.5-8.0 BTDC (red mark on right side of V notch); spark plugs light gray coating - wire brushed and gap checked.
Set car out on driveway for 20 min @ 41F, 72% humidity; light wind, light clouds.
Deck lid open.
9:43 AM - cranked; 4-5 rumbles then steady at 1000 rpm (I tend to like my idle set a bit higher, and advance a tad more, than spec).
9:44 - 1100 rpm; steady
9:45 - 1100 rpm; steady
9:46 - 1000 rpm; steady
9:47 - 975 rpm; steady
9:48 - 1050 rpm; steady
A little idle dip at 3-5 min, then back up. (The AAR closing?)
5 mi drive to hardware store; ~ 15-20 min. Warm start @ 900 rpm; steady
7 mi drive home and around the block; ~ 15 min. Shut off. 45F. Full warm start @ 1000 rpm; steady.
Decel valve working fine (though still want to check it and adjust to 20 if needed)
Looks like all fine here in NJ!

Van B: I like where you're going with this....

It was 30F this morning. Took almost 8 minutes of cruising before the aar called it good. I assume it's the same part.

Fwiw I stole the bellows off a 1.7 van engine laying around in a friend's garage.... Seems to work well, my engine runs super cool though.

SB, what is your idle set at?
That's not much or a high idle but at least things were moving in the proper flow.
Thanks for the vote of confidence too lol!

to me that sounds right for an AAR.
- would align with about how long my engine seems to be taking to get to something close to semi warmed up. the AAR is a different beast on the D jets.



thanks @StarBear for the weather report in NJ.
and countdown info.
does sound like the AAR on yours dips out a little bit early too - but is in better shape than mine and not in such a hurry.


pretty funny in the end.
whole thing is a kind of cuckoo clock bit of krautrock technology in a good sort of way. everything is timed but not necessarily very much is reactive.

Van B: After tune up I set idle screw at 1000 rpm. The car has always run best on cool dry weather.

Ok that’s good info. So, your cold start high idle is only about 100rpm higher. I would ignore the heat soak start you had while out running errands. That’s typical of any engine, IMO.

i know what you are saying.

be interested to see what you find.

i'm kind of curious about the way everything is fine on mine for 2 minutes and then there is a problem for a short amount of time.

i'll be asking mechanic at workshop about it today to see what he thinks now i can describe accurately the sequence.

here is what mike (mechanic) had to say after i showed him the cold start description.

its either starving for air to burn the fuel its getting. AAV.

or its lean and does not have enough fuel. CHT.

as a starting point.

don't you love it.

but apparently it can be either.
there is a lot of fuel being splashed in there and a lot of it is condensing on cold surfaces so the air bit is important. car needs basically 10 times the amount of fuel at cold start up than when its warmed and at operating temp. i didn't realise it was that quantum!

he reminded me, it had been laid up for 15 years.
so you run it for a few months/year and see what faults develop if any.

in my car it could be that the CHT has started out ok and has progressively begun to "decay". have to retest.

or its the AAV. not opening correctly. either not opening enough at the start and not closing smoothly and timely. have to retest. he did say that 2-3 minutes was actually about right usually unless its really cold. then the thermo strip/spring is going to take longer to heat up from the colder engine block and ambient air and go a bit slower.

the thermo and cooling flaps were discussed. they could be playing into the hiccups speculated for either of other two - ie exaggerating them when its a bit colder here.
but they weren't really impacting a year ago he agreed. (i can test that with the car doing a cold start on the hoist by simply pulling on those flaps manually and easing them off, the cable is still there - which i might do when i get around to doing the other tests).

re emorygt350 idea of taking off a hose. yes. do that but....its a closed system. start the car with all hoses on. crack off a decel or aav line between aav and plenum carefully. you want to mimic an AAV valve if thats what you are after simulating. its a small ish aperture thats opening in the valve. so just crack it off like at one edge and control it.
one thing to remember is the AAV is in circuit with the AFM, so the flap might be being slightly opened with the AAV full open. i don't know that for sure, might have to dig around in the manual to see what it says.

as to what a cold start up is for a 1.8 - his view is - probably not that dramatic.
system would be trying to hold something like a normal idle from start up and not a lot more. maybe around the 1000 +/- rpm mark subsiding to 900 +/-.
and it would take anywhere from 2 minutes to 5 minutes depending on ambient.
but in australia he thought 2-3 minutes.

i'll wait until christmas to go further.

I’m running Ljet on a 2056 with a 9550 cam

Cold start always requires a little bit of gas pedal, it doesn’t idle high and threatens to stall if i take my foot off. But cold start has improved greatly with the 123 distributor, and by the time I drive out of the neighborhood it is pretty much good

I think I do recall others having similar issues with anything other than stock engines

It runs fine otherwise

I hesitate to add a cable/rod activated idle increase device…

Yeah, definitely if you are going to pull off the plenum. If you just pull off at the air cleaner (pre AAV) then nothing changes to the system. You then put your thumb over the line and see what happens. Do you feel it sucking? Then the AAV is open. You can let it warm as normal and keep checking on whether it is still sucking. When the idle dips that is when you would suspect the AAV is closing and you should feel it stop sucking. If it is still sucking when the idle dips then you know it isn't associated with the AAV (or at least not directly).

Or you could be like me and just install a valve right before the air cleaner.
Click to view attachment

what i am getting at emery is that in an L jet you have the air flow meter flap up in the aircleaner where air enters. not so sure what D jet does, don't know anything much about D jet at all - which is what you have.

the flap is reading air flow which is also feeding info into the ECU for fuel.
if the aav in cold start is pulling in enough air that it is moving the flap thats going to be part of info controlling fuel flow maybe (as well as engine temp from CHT etc).

i was being cautious about the effect of pulling off a hose and the effect that has on more than just the AAV in an L jet engine. maybe not as simple as simply leaving off a hose.
see Van B's experience when he tried a start with a hose off.

that tap of yours is great as a test device i think.
it might be just the thing.
plumb that in where the AAV is and do a manual simulation of an AAV and timed.
that would keep the AFM in the equation.

Yes this is way different ljet to djet but the aar pulls clean air pre flap. Pulling the hose off the air cleaner will not mess up the flap in any way, that is why I am suggesting it rather than a controlled leak off the plenum. This way you can monitor the activity without disrupting our very sensitive ljet.Click to view attachment

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?

Emery, AFM is attached to the air filter housing. It's the sunset box on that diagram.

Subset* stupid autocorrect

Wow! That is nuts! I had looked at the layout in the Chilton's but it never hit me it was pre everything else. It seems insane to measure total air entering and then try to use a part of that total air to modify the afr. In fact it still doesn't make sense. Cake and eat it too. I must read....

Wow, so basically a pot on the throttle and a TPS on the flap, and the aar cheats the TPS on the throttle by sneaking air without moving the throttle plate. Interesting, and explains the extreme sensitivity to vacuum leaks in ljets. If it is all based on ratios of signals between those two pots...

Yeah, squeeze away or get yourself a good hydroponic valve like mine....

@emery350gt

thats the point of L jet.
its actually way simpler than D jet in most ways.
its measuring air flow into the engine, what your throttle wants, before it gets to the throttle. its all downstream of the air flow meter.
which is why it plain doesn't like air leaks.

its pretty much what EFI became from then on for a long time.
just got more sophisticated with more sensors and more real time feedback.

L jet on a 914 is the proto system. its the adam or the eve, take your pick, of EFI that followed.

thats why i bought my 1.8 30 years ago.
i'm a geek. or i was one.
too old to be a geek now, just a geezer.

or another way to see the aav is a temporary throttle plate for warm up only
but its still moving the air flap because its got to.

More of a kitchen timer really lol…

Not sure if I would say simpler than djet, possibly more adaptive. As far as moving parts we are about equal. Us djets just have that crazy mps going on instead of your flapper.

And we both have the egg timer... And the decel valve. Talk about cruft.

hooked up to a cuckoo clock and a windmill!

Actually, there is no "TPS" on an L-Jet system. There is only a idle switch and a wide open throttle switch, so the ECU only knows those two states of throttle movement. And the 912-E didn't even have the WOT switch.

It was that way on the evolution of L-Jet called DME until 1995. The 964 has a switch like the 1.8L L-jet that only shows WOT or idle. The first DME to get a real TPS that actually measured throttle position was the 993.

Clay

Crazy. I am surprised just the flapper can tell the engine everything it needs, very cool. Just thinking of all the potential combinations like part throttle decel (high volume moving past a small throttle opening) vs very open throttle chugging at low RPM.

With the L-Jet system, there is more than just the flapper. There is the cylinder temp sender, the air temp sender (located in the air flow meter), and the engine RPM. The throttle position is extrapolated from the RPM and the air flow meter information.


Clay

the master has arrived ( @ClayPerrine ). good.


@Van B .
re AAV.
porsche used the AAV on 1.8s all the way through to the first series 944.
in the 914 PET it has a 944 PN (944 606 103 00). i guess its a supersede part.

i did a bit of searching - 944 AAV problems.

this thread is good.
someone figured out how to really clean them out.
seafoam? got more gunk out of it than carb cleaner.
he further shows how it might be possible to adjust it?

https://rennlist.com/forums/924-931-944-951...tibility-2.html

I don't see why you have to fix them....

You can get a direct, bolt in replacement from FLAPS. Just get one for a 79-83 Datsun/Nissan 280ZX. It fits with no mods at all.

Nippondenso built L-Jet under license from Bosch, so it is an exact copy of the Bosch part. And it is not as expensive.

http://www.2040-parts.com/280zx-280-zx-oem...datsun-i421153/

Clay

Awesome! Thanks, Clay!

Thanks Clay !!!

Yeah, I’ve seen that thread. Can’t wait to be home so I can get back to sleuthing!
My little experiment should confirm a direction to focus regardless of outcome.

Oh, and none of these AARs are cheap anymore…

What the hell is “FLAPS”? I’m not into alternative lifestyles just to let everyone know lol!

FLAPS - Abbreviation for Friendly Local Auto Parts Store. The place you go to buy motor oil and wheel bearing grease.

Ah ok hahaha. Yeah, I’m into FLAPS!

Tried it; reminded me of how much I dislike that site - WAY too many pop up ads and crap that only freezes up my computer. Never was able to check out the cleaning comment.

Thanks for the datsun tip @ClayPerrine .
think i can rustle one of those up down here.

i have the same problem with that site,but can work it if i shut some ad pop ups.

here are the screen grabs, its only one guy and two comments that are relevant.

Click to view attachment

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