checkmate1996

that sounds about what I expected...

tailpipe

Doug try hitting one of the VW forums and see if you can buy a used one. They are very common someone close may even give you one for free...

Doug_B_928

I have it at the local diesel shop for testing and cleaning. Will be $25. The guy who does it is on holidays until Tuesday. I checked the fuel delivery without the cold start injector attached and it's getting plenty of fuel, so I'm hoping that cleaning the injector fixes it.

@ Tailipipe: good idea re the VW guys. If it's not the cold start injector I'll be calling you for that WUR tutorial.

AirtekHVAC

Doug,

I am late to this thread, and going through a lot of the same things. I got mine running well, but it is acting like it is only running on 7 cylinders.

Did not see if you tried this, but I went with Mercedes injectors. They work very well. A little shorter than stock, but seem to work fine. The part number is in my #30 thread, I got them on eBay, refurbed, all 8 for like $60

When I save a few bucks, I'm going to buy spares.

Subscribed.

Doug_B_928

So the diesel shop tested the injector and it was find and did not need cleaning. Now I'm wondering if the low cold pressure is the problem. When I last tested the system the only thing out of spec was the cold pressure (14 psi and should be 25-30 IIRC). Maybe the pressure is too low to inject enough fuel through the cold start as well as the other injectors, which would explain the rough cold start. Does that make sense, or, if this is the case, would the car continue to run rough beyond the first 10 seconds or so (which is not the case; i.e., it's only rough on roughly the first 10 seconds of the cold start and then it runs fine)?

jpitman2

If it runs fine after it warms, it should mean the warm control is roughly OK - might still be rich - check that control comes up to 40-45psi when hot through. System pressure is whats used to feed the cold start injector, NOT control. Low cold control should mean its TOO rich cold, which might explain it running rough then. See if the exhaust is sooty and smells of gas while its running rough, which would indicate its too rich. It could also be the Thermotime switch is not open enough when its cold - have you checked this? Mine was like this a while ago, I think I have posted on this before.
jp 83 Euro S AT 55k

Doug_B_928

Thanks, JP. My system pressure, after the new accumulator, is good. My TTS is also new. The exhaust is never sooty, but it always is a bit rich smelling. I've read other posts indicating that the cats (original) are probably long ago not doing their job and so that would explain a bit of stinkiness. I've used the colourtune to check for richness and I have it set maybe just slightly on the rich side. The car seems happy there. The car has had the same rough cold start for at least 20 years so it's definitely something consistent. When I get a chance I'll take a video of it and post on youtube so you all can see exactly how it behaves on cold start.

jpitman2

I think I mispoke in my last = If the mixture cold seems ok, it might be the aux air valve is not open enough (NOT the TTS!), which I have posted about before - low, rough idle initially, occasional stalls, but once warmed a bit it idles OK. Pull the front input hose off the AAV , and while fully cold, you be able to at least get a pencil right through it. If its all difficult to do this, pull the rear hose off, and shine a line in the rear, and look in the front - there should be an opening with shape like a Pac-man visible at one side.
This thread has a video of one closing.
https://rennlist.com/forums/928-foru...-question.html
Mine was not fully open cold, so I opened it up (drill out rivets), chilled it, bent the spring anchor until was fully open, checked by chilling again, then checked it closed fully when hot, all good since.
jp 83 Euro S AT 55k

Doug_B_928

I tested my AAV earlier this summer. It behaved as expected. When cold it was so open that there was, IIRC, a second little opening that was visible. Then I connected it to its wiring and put power to it and watched it close. It seemed to work perfectly. I think the WUR, fuel injectors, and fuel distributor are the only things I haven't touched yet. I'll post a video as soon as I get a chance to take one.

Doug_B_928

Here's a link to a youtube video. Sorry for the poor quality. I should have had the window open so that the engine would be more audible. It fires right up, then the rpms immediately drop and it sputters away (if you listen carefully you can hear it) and then it catches (on its own; without me ever touching the gas pedal) and goes to a high idle until it warms up.

http://www.youtube.com/watch?v=Jyd2e...ature=youtu.be

jpitman2

Sounds pretty good to me...rough running is very brief really. Depending on the temperature, the 1100-1200 idle seems ok, as long as it settles back to 750+/- 50 when hot through. Maybe check to see if the exhaust is REALLY sooty or smells STRONGLY of gas while its rough - maybe the cold start injector runs too long, which could be caused by the TTS being closed too long.
jp 83 Euro S AT 55k

Doug_B_928

Yeah, the rough running is short-lived. The video doesn't adequately reflect the roughness. Once in a while it stalls during that short rough period. If I shut the car off right after starting it, it always fires right up smoothly. It has to sit for a couple of days before it will have a rough start like that again. Still makes me think it's some kind of lack of pressure for those few seconds.

There is no super strong fuel smell during cold starts. However there is always a richness to the exhaust smell; not just at cold start. Nothing tar-like nor smokey coming from the exhaust.

jpitman2

Have you had a gauge on it at startup to watch if its a pressure issue? Both system and control will be relevant. Have you had the hot running mixture checked and adjusted to spec? If it smells rich when hot, it might be much richer than it needs to be at startup, and it takes a few seconds to clear. Mine ran rough cold once, and occasionally stalled, but it lasted a couple of minutes, and was fixed by checking and adjusting the aux air valve.
jp 83 Euro S AT 55k

Doug_B_928

Hmmm....I didn't run the engine with the fuel pressure gauge connected. I guess my next step will be to wait until I can let it sit for a couple of days, then connect the CIS test gauge and start the motor to observe the pressure during rough running.

SMTCapeCod

Did you get it resolved?