02 sensor vs idle

[steve1ph]

ok, i swaped out the aic valve from my stock tb put it all back togather started the car good idle first few minutes then it jumps up to 3k. as iv said befor its running super rich. so got to thinking the o2 sensor is detecting a rich enviroment and the computer idles the car up to compensate. seems that was it cause i unplugged the o2 sensor and drove it around the block now the idle doesnt move. could this actually be the problem? now what do i do about the rich mix?

 

[Hib Halverson]

ok, i swaped out the aic valve from my stock tb put it all back togather started the car good idle first few minutes then it jumps up to 3k. as iv said befor its running super rich. so got to thinking the o2 sensor is detecting a rich enviroment and the computer idles the car up to compensate.

That's not how the system works. The IAC is controlled by the ECM but not directly in relation to O2S input. What does happen is, if the engine is in closed loop and the O2S detects a rich mixture, the ECM will dial-back the fuel trim (aka "integrator") until it reaches it's limit then turns the light on.

seems that was it cause i unplugged the o2 sensor and drove it around the block now the idle doesnt move. could this actually be the problem? now what do i do about the rich mix?

When you swapped the IAC, did you run the IAC learn procedure listed in the Service Manual?

When you unplugged the O2S the check engine light should have come on. That alone may elevate the idle speed. If the light didn't come on with the O2S disconnected, then either the SES light bulb is out, there is a serious problem with the ECM's OBDs or the calibration is way screwed up.

My guess is, as this engine is quite modified, the real problem might be improper calibration.

Also, if you don't have a factory service manual and it's diagnostic information, you're lost. Guessing how the system works is probably not the best way to address this issue.

 

[steve1ph]

hib, thanks my guess is your proble right. way out of wack. no the check engine light did not come on ( it does work) with the 02 unplugged. well with it plugged in it will idle for a few minutes then will rev to 3k and stay. with it unplugged it idles with no problems. also now the fans will not come on with the sensor unplugged. befor i swapped intakes you could unplug the sensor and both fans would come on. i belive that is the same as a detected sensor failure. now nothing. yes i do have the dealer shop manuals electrical and mechanical i guess when all else fails read the manual. by the way if anybody is interested you can get the dealer books from helminc.com. mine were 90 bucks.