Yo,

I had some exhaust work done on my car yesterday afternoon. On my way home from the exhaust shop, the car began to run really weird. Once I got going, speed does not seem to matter, the engine would surge and buck. You could here it kind of "fix" itself and then, bang, it would take off like nothing ever happened. While in the surge/run horrible state, it had no accleration, but it would not stall if I came to a stop. I did pull over to the side and look under the hood. I turned car off fully expecting it to not run at all. It started up and I began home, only to have it start doing the above again, this time I just went with it because I was moving along a long staight part of the road. Eventually she "fixed" herself again but the "check engine" light came on. Code 45, O2 rich. After that, it would run fine.

Today, I thought maybe the welding on the car would have messed up the PROM, not likely but quick, easy to check. No change in above. I have a spare ECM, 7730, that I know is in good order, no change again. I have not yet plugged the scanner into it take a datalog, I wanted to see what anyone thinks.

Here's what I need. We did relocate the O2 sensor into the header from a few inches down the pipe. I don't think that would matter, but I wonder if the wires are resting on the exhaust and have burned through, would/could that cause a very poorly running engine until the computer "fixes" itself. When it "fixes" itself, I am assuming it goes into open loop. I am using a heated sensor, have been for a while, so I know it gets into closed loop pretty quickly. And could welding some exhaust on the car cause damage to a sensor or some electronics? We did disconnect the battery, but maybe that was not enough...

My car,
1992 Z-28 385cid 7730 ECM

It has NEVER done anything like this before. I drove the car in the morning and then in the afternoon, no problems until after the exhaust work was done. And I am not trying to gather info to go blame the guy, its not his fault as far as I am concerned, I just need to fix my car.

Thanks in advance and sorry for the length...

Ryan

 

I would start with what you did just before it started running bad, if you only did exhaust work I would check the o2 sensor. the shop may have left it unplugged or maybe the wires are laying on the header and have burnt the insulation. the fixing itself could be related to bumps in the road and the wires loosing contact with the header and as such the computer getting good info. when the wires contact the header they ground out and send false info to the computer.

if it was running good prior to the exhaust work it only makes sense that it has something to do with that.

 

That's what I think. I know its plugged in because I was there the whole time the car was being worked on. He's a cool guy, let me hang out and watch. I did notice that he didn't unplug it, just unwound it with a wrench. Maybe that stressed the wiring, I will look into it.

Thanks...

 

I jacked the car up to check the O2 sensor. The wires are intact, not burned, no sign of burning, very good clearance for everything. I did slightly pull on them at the sensor itself and all 3 feel kinda loose. I don't know if they are supposed to be, then again, I don't know if any of this is causing my trouble, just seems like a logical place to start. If anyone has any suggestions on where to start, or what to check and how to, let me know...

Thanks


Okay, I took off the O2 sensor just for fun. The wires are very loose going into the body of the sensor and something is rattling around inside it. DOes this sound normal? The thing is about 2 years old. I just don't remember and I don't change enough to remember how they are when new. Little help please... Does anyone think as I do, that this may be my problem???

 

It was the O2 sensor. CHanged it and she runs fine. Strange though, I have never yet encountered that kind of problem...