high/surging idle, running rich

[DSM_JAY]

after a full rebuild of my car 98 GST i have an idle that surges from 1800-2300 rpm's for about 3 minutes once warm it stays pegged right at 2000 rpms. i have replaced the tps had two dead spots, the fuel pressure solenoid had a P1105 non issue now. new MAF. the IAC tested good all sensors that were replaced are OEM. all vacuum hoses are brand new and tight other than that everything on this car is brand new. sprayed brake clean everywhere to try and get a change in idle and nothing. I've been killing myself all week with this car, I need some opinions

 

[TSi Kid]

do a boost leak test and check your timing and spark plugs

 

[FastJetta]

yeah sounds like you might still have a boost leak.... do a boost test like he said.

maybe an idle control motor issue?

 

[Demon33]

A suggestion: make sure your throttle plate (butterfly) is fully closed. You could have a misadjusted (too tight) throttle cable or something is keeping the throttle plate open slightly.

 

[95'RS-T]

+1 on the boost leak test also check your biss for the leaking o-ring. Some say to get the o-ring from the dealer, but I got one from a hardware store and it works just fine sealing.

 

[DSM_JAY]

well i have swapped out 3 different IAC motors, 2 came out of good running cars. BISS o-ring is good. gunna peform a boost leak test tomorrow, have to use the neighbors compressor. what is the likely hood of the FPR being faulty, I never had to replace one hoe would i test it.

 

[EclipticalGS]

Did you by any chance relocate your battery?? or forget a ground? short something??

I still havent figured out why m 2G idles @ 500rpms with no CEL's @ 12.4 afr. perfect crank and base timing.

I think it could be:

front 02 not cycling
Bad ground (from battery relocation)
Bad ECU ground trace
TPS not adjusted right
FPR is bad and maybe getting overrun by a 190lph
cracked FPR vac. line
bad or dirty MAF
Coolant temp. sensor.


Check some of those!! non-cycling 02 wont throw any codes until its fully dead sometimes.

Good luck.

 

[DSM_JAY]

Ok so i did a boost leak test on my car, I did it right around 12 PSI on compressor gauge. while i had the air running was spraying soapy water well the bubbles started coming from the BISS o-ring and from behind the TPS also from one vacum port on the manifold. BOV seal was good. injector o-rings were good. so now do i buy a reman TB or rebuild it myself

 

[black_gsx]

Im having the same issue and stuck big time!! Have no clue what is going on...