I have a '95 Z28 I bought with 117,000 miles on it, (Borla exhaust, K&R intake, 6 sp). I've never driven a "stock" Z so have no reference to go by.

Being a manual trans, I've noticed the rpms would hold 500-600 above idle when moving, then drop to 8-900 idle when the car stopped moving. Is this normal? Also, when starting, the idle would start at 2000 and slowly drop to the 8-900 range, normal?

Now I'm getting EGR, and O2 lean codes, and the idle is all over the place. It started idling a little faster last summer but now it can be at anywhere between 900 and 2500, especially stopping at a traffic light. I'm assuming for the moment the O2 lean code is a sympton, not the disease, so I'm working my way through the various systems.

To idle that high, it has to be getting air from somewhere, doesn't it? The throttle lever is up against the adjust screw so the butterflies should be closed (taking the intake duct off tonight to clean the MAF, so I can check that)

Anyone have any similiar experience with the high idle?
Dave Ahlberg

 

Check out the trottle linkage and make sure the throttle valve is clean, check IAC valve, look for vacuum leaks. You can check out the MAF by pulling the electrical plug. The engine should run the same if the MAF was good, or run better if the MAF is bad.

 

Well this is my first response but I think I can help... The higher rpms when moving is normal, its due to the VSS sensor keeping them up to help prevent stalling during quick stops. The fast idle on start up is also normal to warm the motor up quicker.

 

2k is to high for warm up should be at 1k at warmup and 600 at opreratting temp. do what pete says plus check the thottle postion sensor readings. i would look to the tps, iac motor, air temp sensor and maf. check for any aftermarket chips or add on crap that messes with the computer.