Hi,
My name is jim and I am new at this so please bear with me. I have an 02 avalanch 5.3 with 120k. My problem started when I all of a sudden it was taking the truck a while to turn over. I went and had checker run a test and they said it was the plugs & wires. That didn't work so they ran the test again, this time they said it was the right passenger side ox sensor. Repleced and that was not it then I brought it back the computer multiple engine misfire so I brought it to a mechanic and they ran a test and it said that the 4th cylinder was misfiring so I replaced the plug the wire & the coil for that cylinder, still is not working properly and now I am smelling gas and the plug smells like gas and is black as night. I am not quite sure what to do from here, feul injector replacement? I am hoping to do this on my own if possible it is been quite expensive so far and can't afford to be wrong much more. Sorry this post is so long but any help would be greatly appreciated!

Thanks,
Jim

Well I have a few questions to start with....

Do you have a list of all the codes pulled from your truck? If not can you get them or at least a list of current codes. No need to translate them.

I'm curious as to if you only had a missfire on Cyl #4. There have been many of us that have had plugged cats that caused missfires but it tyically will not effect only one cyl. One may have a higher missfire count but there would be more than one cylinder missfiring.

What code made you change an O2 sensor? and what sensor was replaced. There are 4 sensors on the truck. 2 (one for each side) before the cats and 2 (one for each side) after the cats. The pre cat O2 sensors are there to detect rich/lean conditions and the post cat sensors are there to detect Cat efficency. They do a little more than that but that is thier main function.

I'm not convinced that you have an injector issue yet. It sounds like you are running rich if anything. This condition can destroy your cats anyhow so once you get things fixed I wouldn't be shocked if you had more issues with the cats. One thing that can cause a rich condition is a bad fuel pressure regulator. This again will typically cause a code indicating that Bank 2 running rich. I can assume Bank 2 because the O2 sensors are named so Bank 1 is the side with Cyl 1 and Bank 2 is the other side.

If you can get some answers to these questions I may be able to provide some more help. If I cannot I have another place that I can point you to.

I typically check this site every couple days but I will be out of town over the weekend on a camping trip so I probably won't be back until Monday at the earliest.

I guarntee that your fuel pressure regulator is leaking, if fixed many , many
4.8/5.3/6.0L with this same problem, hard start, very rough idle, and
dead miss on cyl 4, put a regulator on the fuel rail, it will solve your
problem , you might have to pull the plug on cyl 4 and clean it, its pretty fuel fouled.

Thanks, Chevrolet_Tech,

I replace the “Fuel Injector Pressure Regulator” and it corrected the problem.
02 Chevy Avalanche 1500 2WD - Auto Zone Part 800-329 $45.99
Rough running & smelling of gas, misfires no more!
Thanks Again!