02 sls 120k , i have replaced plugs,air/fuel filters,IAC, and checked for vac leaks the best i could as well as seafoamed/cleaned intake/throttle body all with no effect other than a small gain in throttle response . i keep trying and failing. a few months back the car was running fine, then one day the idle stared goin crazy on me, one minute the idle would be so low i would have to hold my foot on the gas just to keep the car running even after warming up, next minute the idle would be so high it was hard to keep the car from taking off. that problem has somewhat subsided, the really low idle problem seems to be gone.
lately the problem is the rough idle after idling for about 10-15 seconds and constant if the car is idling in gear (feels like surging when the car is in gear). occasionally when i stop the car and put it in park the idle will shoot up around 1800+ rpm and wont bring itself back down for minutes sometimes (i usually turn the car off as soon as i see this start to happen and restart and all is well aside from the rough idle).

my check engine light is not on and i just pulled the codes tonight with nothing showing other than a couple abs codes for the brake wear indicator.

I am puzzled as to what could be causing this and would really appreciate any assistance anyone could provide, this problem is driving me crazy.

 

i think i found my problem, the intake plenum (boot) is leaking on the bottom . im ordering the plenum tommorw along with a manifold gasket because i believe you would have to r&i the manifold. looks pretty straight forward. although if anyone would know what the procedure involves specifically that would be a great help.
or at least how much to torque the manifold bolts. im sure even at my cost the manifold wouldnt be cheap

 

Im surprised that there was no code sent.

 

I was looking for a set of instructions on the same procedure for my 01 STS and found this...

http://www.justanswer.com/questions/...ce-plenum-2001

step by step with pics...
hope this helps