'03 Avalanche problems

If it is the catalytic converter, it might still be under warranty, even tho' the rest of the truck isn't.

Bob

If one bad injector, probablyi not, as the ECM would indicate which cylinder, and you seem to be seeing it on all cylinders. Tried viewing live data and watching the mis-fire counters?

Measure the pressure differential between the cat in and the cat out...

On Wed, 10 Jun 2009 12:31:00 -0500, Tim fired up the etcha-a-sketch and scratched out:

Writing from experience, yes.

Well, actually, the clogged cat wasn't the original root cause, but it sure messed stuff up.

I had a '95 Jimmy 4x4 with the 4.3L V6. The injector in one or more cylinder got clogged and I started experiencing misfirings at around 70K miles. (The injector for this truck sucked!)

After I got the injectors replaced, I was still having issues. I figured the O2 sensors were fried and - upon checking - that was true. Replaced them.

Next it still was running rough. It was the cat.

Because of the other issues, the cat got clogged and needed to be replaced. Did so at about 120k miles and all was well after that, except for the 4x4 system going out. :P