Well I have been searching for the answer for a couple of weeks on here with no luck,

the facts:
-it runs good at speed
- no noticable vacuum leaks
- scan tool shows timing advance is retarded 20 degrees and retarded into the 30's when at higher RPM
- Had a random misfire code once about a year ago, since then no codes at all
- idle drops down into the 400's after reving engine up then returns to 550-600 rpm
- no noticeable misfire above idle
- catyltic converter is shot, scan tool didn't show anything abnormal with the O2 sensors (flip flopping back and forth like the should)

any ideas or more information needed Please let me know. I love puzzles but dang , I've been trying to figure this out for a while.

 

When was the last time you cleaned your throttle body & EGR valve? A dirty IAC valve can stick and cause an abnormally low idle speed. A stuck EGR valve can cause idle quality problems.

 

EGR valve was cleaned out about a year or so ago. It wasn't to dirty then. IAC hasn't been touched. I'll take a look at that tomorrow and report back thanks!

 

what is an IAC valve? also did you check your lower intake gaskets for leaks?

 

IAC = idle air control valve.

 

Intake gasket isn't leaking, It has already been replaced due to coolant leak in the back side of the engine. Where exactly is the IAC... I know what it looks like but can't seem to find it.

Not in the manual thanks

 

If you take off the air plenum it will be right under it on the drivers side

 

The IAC valve is on the back driver side of the throttle body.

 

found it, cleaned it, idle is steady about 600 +- rpm . Still has that stumble though. Is it normal for the ignition to be retarded so much? I checked it again yesterday and at idle it's retarded 20 degrees. At higher rpm's it's retarded upto 40 degrees. that doesn't seem right to me, but then again I don't know what I'm talking about

 

have you ever replaced your spider injector before? hows your fuel filter?