[V8] rough idle (update)

[urq]

... that other tube is where the crankcase ventilation hoses enter the
intake tract ...

There are a lot more paths involved with a rough idle besides the intake
tract.  While the MAF could be a culprit it would be an expensive experiment
with a probability of less than 50% success IMO ... I would not suspect the
ISV/AAR unless the idle speed is wavering ...

Does it do this when the car is first started?  If the behavior occurs after
the engine is warmed up I'd suspect something like the OXS ... or perhaps
one of the inputs to the ECU like a temp signal is wrong.  Rather than
spending $200 for a MAF, spend it on a copy of ProDiag or VAGCOM ...

My tuppence ... with appropriate IUD
Steve B
San Jose, Kaleefohnia (USA)


> Well, I just got sick of my rough idle the other day, so I took every part
of the air intake apart that I could and cleaned them all, even though they
were pretty spotless.  I also serviced the K&N.  These two seemed to help a
little, as the idle is not as rough as it used to be, but it is still far
from purring.  That makes me think that the culprit is an air measuring
device.  Could a MAF make the idle rough?  Idle control valve is working
fine and clean, but could it be gone mechanically/electrically?  I also
noticed a few other holes with hoses running to them; are there other
sensors that I should know about?
> Also, something else that might help.  Before I had the low rough idle, I
had a high idle.  It would not be present until about 2 minutes after
starting the car, then, just like someone threw a switch, it started to idle
high.  I think changing the OXS helped out with that problem, but oddly
threw it the other way.  I probably should run a VAG-COM to see what it is
saying now.  Anyone near Nashville, TN?  I'll be in Birmingham, AL this
weekend if that helps.
> One more thing: before the throttle, the air is "chambered", for lack of a
better word, into 3 chambers.  Two go to the throttle butterflies, the other
goes to a hose.  What is that hose?  It goes right next to the right bank of
cylinders, and it had a little oil...