Hi
I have a 1995 Sl2 with twin cam engine and Auto trans. I bought the car with a blown head gasket and it did not run. I got the head redone and put it all back together. It starts right up, but revs at 2800 to 3000 rpm and wont come back down to idle. Another thing it does is when I put my hand over throttle body hoping to choke out motor, it did not come down in rpm. The things I have already changed are, vss, mass air sensor, and tps. If anybody has any sugestions on what this might be, I would really appreciate it.
thx

 

when you look at the position of the butterfly in the throttle body, what is the positon? 'Cause if it is closed, there is probably a hell of a leak somewhere betwen there and the point the fuel is injected into the intake manifld. If it is partially open then find out why!

 

The throttle body is closed all the way. I took the whole thing off and cleaned it as it was covered with carbon and soot. I will look for another leak. Yesterday I started spraying around in there to see if there was any vaccum leak. But no difference in rpm?

 

Maybe try cleaning the egr, they can make the motor do some crazy things.

 

Seem to me if the throttle butterfly is closed, putting your hand over it does nothing, spraying something into it does nothing effectively determining it does nothing, but the engine is running at 3000 rpm, there has to be something between it and the engine that has a good size hole in it. The engine is getting air from some where and if it aint from a closed butterfly in the throttle body, it's got to be somehing else. And what ever it is, is between the throttle body and the cylinder head.

 

check PCV to throttle body hose
disconnect electrical connector from EGR

(separately)

 

It happened to my wifes car. Its an "Idle Air Intake Valve" that needs to be replaced. About $70 in an auto store to replace

 

My EGR was causing the same thing.

What I suggest for any problem like this with almost any car is to do a smoke test before anything else if you have a smoke tester or know someone who does. Smoke tests are cheap and effective ways to find vacuum leaks.

 

Other than setting your car on fire which is probably not the correct way to do this, is this the equivelent of spraying WD-40 or something equivelent around at potential area's.
I think it is important here for people reading these forums that first time backyard mechanics in training realise that these fuel injected cars are actually quite complex and it realy pays to purchase a Chilton or Mitchels or something service document or better yet, factory literature and actually read them to try to figure out how things work. As many years as it has been I have been fixing my own cars and doing so, allowing me to both own cars I could not afford or own and maintain collections of them I can not work on them with out service documentation now and some tools I never needed before.
It also helps to completly try to discribe what you are attempting to do or understand so some one can give you a complete and better answer for your problem.

 

ok guys, first I would like to say thanks for all your help!!!
It looks like I get the BONE HEAD AWARD. I was going to take the advise and set it on fire when all of the sudden I looked at the back of the manifold on top where the vacuum line goes into the the plenum and the line was off!!!!
And lo and behold I put it on and it idled like it should.

Again thanks for all your advice, and Ill try to not shoot myself for working on this thing for ever!!!