Hey guys, if I unplug my O2 sensor, shouldn't it throw a code and make the CEL come on? When I unplug mine, it doesn't make the light come on.

The reason I ask is because I'm still hunting down the rough idle on my car. Kind of seems like a miss at idle, and it's a little rough up to about 2k rpm or so, but then it smooths out pretty good. Car has lots of power, don't notice any miss while driving it, just while sitting at idle. Here's what I've done:

New plugs all gapped properly, new wires, new PCV, new coil, new TPS, new IAC valve and a new EGR valve. I also plugged all the vacuum ports on the throttle body one at a time to see if it was a vacuum leak, and it still had the roughness while plugged. So I'm thinking it's not a vacuum leak. Checked the injectors, they look pretty good. Fuel is spraying in the shape of a cone and looks pretty misty.

Anyone have any ideas? I've fixed alot of random little problems on this car.. This is one of the last problems I'm having. I want to try and fix this problem before I even attempt to smog it, seems like this would probably make me fail.

 

Ok, I'm kind of wondering if it's a miss or something just imitating a miss. It will be smooth for a second, then get rough, then smooth, then rough.. But it's pretty random, it's not like one cylinder is just consistantly missing or anything. It does seem to run better when it's cold then when it warms up.

Oh, I also forgot to mention, I did replace the CTS.. The plastic connector on it was broken. I was also thinking it might have something to do with my idle. So I went ahead and replaced it, but there was no change. Anyone have any ideas at all? This problem is driving me crazy. I'm gonna be getting my new cat and muffler installed in the next week or so probably, and I need to try and fix this so I can go get it smogged. Thanks.

 

ruff crowd, Brian, did replacing the O2 sensor fix your problem??

 

Nope, unfortunately. Kind of learned to just live with it for now. I'd like to do some datalogging to see if I can track this problem down, but I don't have a laptop to do it. Half way tempted to just take it to the dealer and let them throw it on their machines.

I can't imagine this problem is too serious though, because I did pass smog. A couple of my numbers were pretty high though. I can't remember if it came close to failing or not.. I was just really happy that it passed. lol

 

sorry, thought i read through your whole post ..

well anyway, did you also check/replace your ignition module?