[T3] running rich and mystery material

[Jim Adney]

On 11 Nov 2012 at 12:59, Dave wrote:

> I have to respectfully disagree with you on this Jim. I agree on the stuck
> or not stuck part, and I agree that if your AAR was never adjusted since new
> that is it more than likely set just fine. But in the 40+ years these cars
> have been around mechanics that don't know what our FI systems are all
> about, the factory adjustment could have been changed at some point.
> (probably a bad guess at a solution to a different problem) I'd bet there is
> enough adjustment travel on our AAR's to where there is almost no AAR
> function and it is closed off all the time - or too much air to where it
> never really closes off when warm - and everything in between. I'd also bet
> that in Dennis's case - if his AAR was wrongly set to where it let no air in
> when cold - it would not cold idle well like he is seeing in his video.

You're certainly right that anything could have happened over the 
years, but this whole thread started about richness at idle, and has 
gotten hijacked into AAR problems. I think this is taking us way off 
base.

Now I have to admit that with our traveling, I wasn't able to view 
Dennis's video until just now. The first thing that strikes me is 
that it won't idle (idle is too slow) when cold, and I don't know how 
it does when warm. This could be the AAR stuck closed, the idle 
adjustment closed down too far, or any number of other things.  

It's clearly rich, but this may just be the FI struggling to try to 
keep the rpms up in the face of some other problem. Yes, it could be 
a temp sensor, but that's a long shot given the fact that Dennis has 
checked all those things.

First off, I'd pull off the AAR hose at the air cleaner and plug it 
with my thumb and see if that makes the idle slow down even more. In 
this case, the engine should die immediately. If it doesn't, the AAR 
is stuck closed. I don't think it's possible to misadjust it enough 
to make it close completely at room temp, but I could be wrong about 
that. If the adjustment is all the way to one extreme, Dave may be 
right that it's been tampered with. If so, put it back in the middle.

If stopping the AAR hose kills the engine when it's cold, but has no 
effect when the engine is warm, then the AAR is working and Dennis 
needs to look elsewhere.  

It doesn't sound like it's firing on all 4 cylinders, but that's 
pretty common when cold, and even more common if it's running rich 
for some reason. If everything seems fine once it's warmed up, then 
the ignition system must be okay.

Try removing the air cleaner to see if there's a restriction there 
that's keeping air from getting in.

Look at the pressure sensor. It should have a black plastic cap over 
the adjustment screw. If not, it may have been tampered with. If the 
cover around the adjustment screw has slots in it, it's the wrong 
pressure sensor. Make sure the hose is on there securely.

Look at the 2 wires at the LF corner of the engine compartment that 
bring 12 V to the FI wiring harness. Look for frayed wires or 
anything there that might cause an unusual amount of voltage drop.

If you still don't have a tach, get the engine warmed up so that it 
idles well, then increase the idle speed until the idle starts to 
lope up and down. Then reduce the idle until the loping stops. Check 
it again when cold and reduce it more if the loping occurs again. 
Keep reducing it until the idle doesn't lope at any time while 
warming up.

You've adjusted the throttle valve switch correctly, right? If not, 
i'm sending you my FAQ on how to adjust it. Make sure it's right 
before trying the "loping idle adjust" above.


-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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