oxygen sensors

Daughter's car is a 1995 Cirrus, V-6, 61,000 miles. Its been running rough lately, and the oil pressure light would occasionally come on at stop lights. Idle Speed Control Motor, and EGR Valve were replaced. Took it to a dealer, who allegedly did a diagnostic test. They replaced the oil pressure sending unit, did an overpriced fuel injection cleaning, and said it needed a tune up. I declined the $500+ tune up and replaced the spark plugs, spark plug wires, distributor cap and rotor myself. It runs better now, but not like it should. (interesting side-note, I never saw the oil pressure light come on while I was driving the car - until the dealer worked on it, then it came on several times as I was leaving the dealer's lot. arghhh!!!)

Any problem with the oxygen sensors, should have shown up in the diagnostic test, but considering the alleged work they did with the ignition/transmission recall, I'm skeptical that a diagnostic was even done. So, now I'm thinking, maybe the oxygen sensors need replacement.

My Hayne's manual says there should be three sensors. Two "upstream", one in each exhaust manifold. One "downstream" just after the catalytic converter. I've crawled all under the car. Finally found the two "upstream" sensors. The one on the rear exhaust manifold took quite a bit of looking before I finally saw it. Can't find the "downstream" sensor that is supposed to be after the catalytic converter. Can't find any sort of fitting where it might have been installed, nor any wiring that might have gone to it. Is the Hayne's manual wrong? Checking various online parts sources, some list two different sensors (I'm assuming "upstream" and "downstream"), while others only list one sensor.

Should there be three sensors, if so, where? Any ideas on the rough running?

I have a '96 LXI. The Mopar service manual for '96 shows two oxygen sensors, upstream and downstream -- one in front of the converter, one behind. I recently replaced them when I got a trouble code indicating "catalytic converter efficiency failure." But I also replaced the converter, an "economy" converter that had gone in to replace the factory original. The car now has a third converter, a Mopar converter. It was an expensive job but I think it paid off in performance. I had been having problems diasgnosed as ignition related: extreme power loss, stalling. After a third set of plugs and cables I was still having those problems. I'm still still stalling occasionally, but I no longer have the power loss problems. I'd be surprised if the '95s and '96s are different with respect oxygen sensors, but that's not impossible. I find it interesting that your idle speed control motor and egr valve were replaced. Was the car stalling? How was your oil level when the oil pressure light came on?

I have a 95 Cirrus LXI (sounds like the same one your daughter has/had). I've had nothing but trouble with it since I got it.

After the most recent round of work, here's what it does. I'll be out on the highway between my home and my work, less than 15 mins on the highway, total trip of 20 mins. Sometimes, but not always, I'll lose power on the highway. Most freqently when i'm about to exit and slowing down. I'll get to a full stop and it'll stall out, then I can't start it. The last two times this has happened, the repair place hasn't known what's wrong. The dealer replaced the EGR valve (some moron working on it prior to me owning had glued it back together) and said that the seals around the spark plugs are leaking oil and should be replaced, but should be ok for now.

When it gets like this, it won't start for a while, and when it does, it runs very rough. It'll usually stall out a few seconds/moments later and never gets enough power to move, or rarely. If it does move, its way under powered and not suitable for driving on surface streets, much less the highway.

The tachometer will waver between about 1500 to as low as about 250-ish, a shaky up/down, and then it'll stall. If it sits around for a day or so, though, it'll work ok again. Though its always a little off feeling (not firing properly, I think).

The last time I had it looked at, the mechanic suggested trying some drygas, just to see what happens. While I was under the hood, I went to take out the abs fuse (i'd complained about the feel of the ABS and he said it's easy enough to disable by pulling the fuse) and found no fuse in the downstream oxygen sensor location. Since they're listed as the same size (both 10A) I popped the ABS fuse in there. No real change, but it hasn't died on me yet (though I've been keeping it off the highway).

I don't know if this offers you or anyone anything, but its worth a try...

oh, and does anyone else out there know if there was a reason there would be no fuse in my downstream oxygen sensor slot?

go to your local autoparts store and rent a diagnostic tool. they will charge you a refundable deposit. plug it in and find out what codes the car is throwing.