Got my car serviced, changed the battery. Felt that the idle RPM was a little too high (>1,000). Went back and the mechanic used the Launch diagnostic computer to adjust the RPM but somehow it can't be adjusted....like its stuck and does not allow adjustment. I never had this problem. The mechanic had another 350Z there and proved to me there was nothing wrong with his computer because he could adjust the other 350Z's RPM without issues but not mine.

Cleaned the throttle body, cleaned MAF, reset the ECU, etc. etc. but nothing works.
The car seems to be running fine otherwise.

Suspicion # 1: faulty throttle body.

Any ideas?

 

How long ago was the battery installed?

 

About 1 month.

 

Disconnecting the battery may alter the idle, but it is generally "back to normal" in a couple of days. Sorry but I have no idea what is happening with your idle.

 

First check for any error codes if you didn't. Check the MAF, unplugged or bad MAF wiring will cause high idle . You may also be having a vacuum leak somewhere specially if you have a spacer.

 

I'd look for air leaks.

 

Thanks for the feedback. It could very well be an air leak. I have a plenum spacer installed, and recently had the head gasket changed. Could all be contributing factors.

 

What year is your car and what year is the 350z that your mechanic could adjust? Only very early models can be adjusted with generic scan tools (or UpRev's Cipher). A reflash can adjust any year.

That said, your issue is probably a vacuum leak, likely near the oil filler cap.

 

Mine is a 2004 Japan import. The one he could adjust was a 2003, also Japan import.

 

SO was the problem a vacuum leak??

 

Don't know yet. Will find out tomorrow when I go to the workshop. Will keep you posted.

 

had the same problem once , we tried everything and still idle was high... 1 month after i installed the Cosworth intake manifold and iddle was back to normal.
there's a leak somewhere try to figure it out by removing the spacer and turn on the car anc see if the iddle goes back to normal..