Re: 5KCSTQ - Bad Cold Start==>Bad Hot Idle

["Mark Pollan" <Mark.Pollan@MCI.Com>]

I wrote:

<< After a "long" highway run (1 hour @80-85MPH) she will idle pretty
 well but between 500 and 600 RPM when stopping, such as at a toll-booth.
 
 If I shut her down after she's hot (please, please leave it alone) and
 restart before she cools off (oh go ahead) the engine will seriously
 stumble (below 200RPM) and if I don't give it gas will die.
 
 Help!  I'm catching it from my wife as she does not appreciate the
 finer points of a Quattro.
 
  >>

Scott responded:

<<O2 sensor sounds bad...  See if you get the 500-600rpm stumble at A/C
compressor on....  Could also have a pcv hose prollum, ck the t at the top of
the valve cover, and the hose that goes from that t to the block (small one
end, large as enters block)...  Those deteriorate over time, the t leaks out
of the bottom, and the other hose collapses when hot...  Neat...  Then do the
usual ck of the IC to t-body hose for cracks...>>


Thanks Scott!

I guess a little more info would help. About 20K miles ago replaced O2
sensor. About 10K miles ago replaced all turbo hoses (IC to EM, Air to
Turbo, Torbo to IC) and three crankcase hoses (two mentioned above
plus one going out the other side of 'T'). This sputtering actually
started when I replaced all of these. My cap/rotor and plugs looked
horrible so I tossed all the hoses thinking ignition. Replacement of
cap/rotor an plugs did nada damn thing. Also hosed out ISV with carb
cleaner, nada!

I'm not ruling out O2 sensor but any other ideas out there based on
this new info.


Mark Pollan