I have a '95 coupe with 47K miles, auto. Last week it started stumbling and missing and idling very rough. I babied it home and noted very black soot on the rear bumper fascia and black soot coming out of the exhaust (both sides.) I ran codes and "H-64" came up, translating to a "Lean oxygen sensor, left bank." I cleared the code and started the car and drove it around the block. Ran fine for a few minutes and then it repeated the problem. I again obtained codes and got the "H-64" again. OK, let's fix it.

The fella at AutoZone researched and found the factory original part number and asked: "Front or rear sensor, left or right?"

Front or rear . . . left or right???? I saw only one in the factory manual, and it was shown ad being located on the left exhaust header in front of the cat.

Anyways . . . a "lean" reading would not equate to black soot coming out of both pipes, right?

I did a cursory under hood check for the obvious: leaks, wires, hissing, knocks, etc.

Before I open the Snap-On box and start turning wrenches, I thought I should check with the "gurus" here and get a few recommendations and maybe narrow this problem down.

The car ran great with absolutely no problems. . .up 'til now. I do not "dog" my car either.

Any thoughts?

Thanks in advance, Gary

 

A 'false lean' will result in the ECM dumping too much fuel into the injectors that are affected, therefore the car actually runs rich. I believe the 95 has at least 3 O2 sensors; 2 before the cats and at least 1 after, hence the questions from the autozone guy. Lean on the left bank suggests the pre-cat O2 on the drivers side. I'm no expert, so please wait for the gurus to pitch in!

Oh - and I think the resonator on your system is actually an H pipe, so yes, you could get soot out both sides..