: help, 99 catera eratic idle in park

11-29-08, 08:15 AM
I am working on a 99 catera 3.0L for a neighbor.He has had it to the dealership and they cannot identify the problem. When the car is started from a cold start it idles and runs fine.Once the engine is warm it idles up and down from 600rpm to 2500 rpm,constantly up and down between the two rpms.If you put the car in reverse or drive the idle goes to normal under a load with no surge at all,it only does this in park or neuteral when the engine is unloaded.I have pulled the throttle body and seen when I removed it that there was alot of oil inside the intake manifold and the throttle body was sludged up really bad.I dont know if the evac system has anything to do with the idle system but I thought i would fill you in on that detail.This is the first cetra I have worked on and I am very unfamiliar with the vehicle.Also I don't have anyway of checking diagnostics on it but the owner stated that the dealership found 9 trouble codes.Any help greatly appreciated Thanks!