You would think that a bad rear O2 sensor would cause a CEL. You would also think that if you unplugged your rear O2 sensor (regardless or being good or bad) would trigger a CEL. Well, I tested my rear O2 sensor this weekend and found that it was bad, but my PCM does not trigger a CEL. I now have the O2 sensor unplugged from its harness, the car still drives ok, but no CEL. I have reset the computer, no CEL. I can unplug other emission devices (ex. EGR solenoid) and get a CEL. Of course I plug it back in and the CEL goes away after 3 key starts. (just like it should) Should I replace my rear O2 sensor? Or is my PCM just not ever going to read or acknoledge my rear O2 sensor.

The car runs like hell, burns way too much fuel and the throttle response is horrible. When I start my car (warm or cold start) the RPM's goto <2000 and then slowly come back down to wherever they need to be. Does you car start like that, or do the RPM's just flip on to idle or fast idle? If you rev my engine to 5000 rpm's and take you foot off the gas, the engine will sit at 5000 rpms for a sec and then slowly come back down. If you stomp on the gas at idle, there is a good half sec to one sec delay before anything happens.

There is a small check valve that is connected to a vacuum line off of the passenger side intake plenum. This line is on the left side of a three way connecter on the back of the plenum. There is a little bit of hose, a check valve, and more hose that goes to the EVAP solenoid. On this valve, (mine anyways) there is an arrow pointing in one dir with the word 'engine' under it. For some odd reason, this arrow points in the dir of the solenoid not the engine. I need to know if someone elses car is like this. I will try and post a pic of the check valve if I can, but it is a small plastic thingy with a green cap on the top.

I am very close to figuring out what is wrong with my car. Thanks in advanced for all your replies.

-Jared
96 GS
Melbounre, FL
AFX Pulley | Iceman CAI | Generic Ractive Muffler <- LOUD

Dave, I want to go for a ride in your car! Perhaps a test ride in your turbo dsm will inspire me not to sell my car after all the crap I have been through with it.

Iceman CAI | RS*R Cat-Back | AFX Pully | Milled Head 10:1 CR | MP 60mm TB

yeah man i ave two things wrong with my car that makes it do something similar to yours with the hangin rpms. first off i think i have a bad idle speed controller. wheni started mine it used to jump up and then eventually die down to 1g even instead of goin all the way down to 750 but my next problem came. my SECONDARY AIR SOLENOID went to hell. and it causes the O2 sensor to go off and my engine bogged. over time the bog has gotten worse, so bad that i don't think i would be able to start it if the idle speed jigger worked right. if your engine light isn't on look around your throttle body for a hole, yes a hole. if you find one you need this special screw that fits in there with a o-ring you can find that on dsm.org they call it like tssc or something abbreviated.