Pulling the Plenum for the first time...

[Billy Mild]

I forgot to post a few pictures. I should have taken more, but we were trying to get things done.



Oil vapors were being vented to the atmosphere. I don't understand how this car ran at all.



In this picture you will see a mouse nests. Guess what? There was a crispy dead mouse still in there. Surprisingly there are no chewed wires.

[Schrade]

Originally Posted by Billy Mild

Now the fun starts...

Marq21 and I pulled the plenum on the ZR1 yesterday. Need to give him a shot out for helping me out on this job. Without him I would have not been able to fix the secondaries issue I was having, or get the complete job done.

First off, WOW. The car runs completely different. I don't even know what to say. If your car doesn't surprise you every time you hit the gas WOT, then you need to get some service done.

My car is having an intermittent high idle issue. It doesn't sit at the prescribed 750 RPM. It idles around 900 rpm normally, and occasionally after coming to a stop will be at 1200 RPM. With a Tech 1 hooked up the IAC shows 0. It occasionally would move, but at idle it was 0.

I have read there is IAC re-learning procedure that can be done. The battery was unhooked for a few hours. I have the FSM, but I don't know the correct search terms to find it.

-Vacuum leaks were fixed
-Plenum gaskets were in good shape so they were re-used
-Accell Injectors were installed
-Check Valve replaced for cruise
-PCV Breather hoses in the valley were replaced
-New MAP hose

The car runs great throughout the RPM's now. It drives great, except idle is a little weird. In between gears the idle will kind of hang around 1500 RPM.

Sounds like the High Idle Coast-Down issue, for which there was a GM TSB. Marc H has the chip code solution...

You might ALSO have air getting by the TB 2' butterflies, as I mentioned above.

Mouse needs butter (he's toast)

[Billy Mild]

I didn't remove the TB at all, also I didn't clean the inside of the plenum at all.

[XfireZ51]

Originally Posted by Billy Mild

I didn't remove the TB at all, also I didn't clean the inside of the plenum at all.

Did you remove the throttle cable?

[Billy Mild]

Yes I did remove the throttle cables.

[A26B]

Did it idle properly at 750rpm before you did the work?

[Billy Mild]

Originally Posted by A26B

Did it idle properly at 750rpm before you did the work?

In general the car didn't run very well before this work. But it did have a consistent idle.

Now the car runs better, much better, but the idle is not consistent. As far as I can tell there aren't any vacuum leaks. I tried spraying potential vacuum leaks with WD40.there was 0 change.

Could be TPS or IAC possibly?

[A26B]

I doubt that its the TPS or IAC, if they were not removed. I am more inclined towards a vacuum leak associated with the work that was done. Its not unusual to have a cracked hose or leaking connection when re-installing the plenum. It's a little tricky keeping it all connected. You should backtrack your work.

[Billy Mild]

Is there anyway to check this without pulling the plenum again?

[mike100]

take the intake bellows off and take a stiff box cardboard piece (like real stiff) or a phone book etc and block the air horn to see if you can stall it. An open tube will be audible enough if the engine is still running at that point.