Idle surge driving me crazy

[Fern-tsi]

Idle surges like crazy from 800 to 1200 at stop lights. Very annoying with 3" exhaust.
No boost leaks, New O2, new biss Oring, logger showing ISC zero at idle.

 

[steve]

No boost leaks, New O2, new biss Oring, logger showing ISC zero at idle.

The fact that the ISC is at 0 steps at idle indicates that the ECU can't lower the idle speed enough. So first adjust the BISS until you have 10-20 steps at idle or find the source of air bypassing the throttle plate if the BISS is all the way closed.

 

[Fern-tsi]

So can i assume that the ISC is working properly? I've screwed in BISS and new O ring, Checked for boost leaks.

 

[steve]

So can i assume that the ISC is working properly?

No, why? You haven't shared any information on the ISC other than it's at 0 steps which means the ECU thinks it's all the way closed. Key word is thinks that doesn't mean that the ISC actually is at 0 steps.

 

[Fern-tsi]

Ok ISC tested out good 30+ ohms and applied 6v.
Did another boost leak test and i hear a steady leak coming from either the bottom of the Intake or side of TB, possibly shaft seals?
Would buying a rebuilt TB be worth it or are the seals an easy replacment?

 

[steve]

Would buying a rebuilt TB be worth it or are the seals an easy replacment?

The seals aren't too difficult but if you have a problem getting the screws out of the shaft you can wind up cussing a bit.

A rebuilt TB is a easy swap if you have the cash to spare.

 

[reddragonvr4]

IdleSpeed - DsmWiki

might help it sounds like your problem.

 

[laser92DSM]

It could be your FIAV that happened to me in my 92 Laser i just bought a block off plate and fixed it.

 

[Fern-tsi]

Ok fixed one problem and created another. I fixed surge problem by rebuilding TB myself, new FIAV gasket ,shaft seals, Biss screw and Oring, and cleaning.
Idle surge cured but high idle, as in 1300rpm's. i adjusted idle stop switch. I think i cleaned the bore a little too well and now its not sealing (air creeping past butterfly). What can i use to seal fine gaps?

 

[steve]

The IPS (Idle Position Switch) adjustment is critical. Make sure you don't have it holding the butterfly too far open.

Also check to make sure that the plate is centered in the bore. If you removed the sealant from the back side of the plate you may be looking for another TB.

 

[Fern-tsi]

FIXED !!! purrrs like a kitten now. Thanks to the classifieds on this site i bought a used TB and rebuilt it.
A little tip (like Steve has said before) don't over clean the bore with carb cleaner as this can remove some of the factory sealant . Had i searched a little harder i would've seen that Oh well live and learn.

 

[dsmspickdad]

Always read the all the threads related to your issue it will save you time, money, and the headaches. I am gald that I am not the only one.

 

[binx]

not to thread jack but mine is killing me too , I mean should your car take 10 minutes of warming up even when its warm out ! to idle right? mine idles at 2000 on startup then slowly goes back down to 1000-800 , but say I get in it before its all the way warmed up it will idle at 1000 but when i back out of the driveway in neutral , it doesnt surge it just goes to 1500-1600 until I take my foot off the clutch , was 1-2 seconds and it goes back down , but once were moving again and I come to a stop it will idle at 1500 until I let the clutch out. WTF?