running rough, misfiring

rebel77 · January 23, 2006

I am having trouble with a 03 silverado with 38,000 miles. 5.3 motor 4wd.

I am getting several codes, dont have them with me. The codes were for too lean a mixture and misfiring. Autozone said it showed the oxygen sensor. I changed that along with the fuel filter. I reset the computer. The SE light has come back on and the truck is mis firing and running the same. It does not do it all the time. Most of the time it is when I am stopped or coming to a stop. I am going to try the cap wires and plugs. I thought it might have been water in the gas, still have not ruled this out. Autozone said to change the plugs and wires. He tried to tell me that the wires need replaced every 20,000 miles???

Any other suggestions?

az'03Silverado · January 23, 2006

Did you change all of the O2 sensors? I think there are 3 of them. Also look at the wiring to the sensors. If they are chaffed or broken or anything like that it could fault the system even intermittently. And you're right about the plugs. They don't always last 100000 miles as advertised so it probably wouldn't hurt to swap them out with new wires. Did it give the same codes the second time?

redvett · January 23, 2006

I am having trouble with a 03 silverado with 38,000 miles. 5.3 motor 4wd.
I am getting several codes, dont have them with me. The codes were for too lean a mixture and misfiring. Autozone said it showed the oxygen sensor. I changed that along with the fuel filter. I reset the computer. The SE light has come back on and the truck is mis firing and running the same. It does not do it all the time. Most of the time it is when I am stopped or coming to a stop. I am going to try the cap wires and plugs. I thought it might have been water in the gas, still have not ruled this out. Autozone said to change the plugs and wires. He tried to tell me that the wires need replaced every 20,000 miles???

Any other suggestions?

<{POST_SNAPBACK}>

First of all the GMT800 trucks have no distributor and with 38000 mi the plug wires arent bad but i would check out the fuel pressure regulator. If O2 sensors are bad they are under warrenty until i believe 80000 mi. See if vacuum hose on regulator has fuel in it if so its bad.

rdalley · January 23, 2006

I just experienced the same thing, but it left me stranded on the interstate. It was a bad fuel pump on an 03 Avalance. It caused a misfire code and blinking engine light, lean mixture etc.

I need to rant about it, too. Who the heck designed the fuel system on the avalache?? Its a 3/4 ton with the 8.1l engine. Apparently it has 2 tanks. The front tank has a pump that pumps the fuel to the engine. The rear tank has a pump that pumps the fuel to the front tank as it is being pumped to the engine. Our rear pump failed causing the front tank to run dry and leave us stranded. Seems like they just engineered it with more parts to fail!

97chevy350 · January 23, 2006

I have a very similar problem on my 97 (350) except im not getting a lean mixture code. Lean, should rule out fuel press. reg. Does it start right up? Turn just the key on and listen if hte pump sounds healthy. I think my problem may be a couple of bad injectors.

rebel77 · January 24, 2006

I am a rookie at this stuff, so I apprecciate the help.

I have now changed the fuel filter and one oxygen sensor.

Last night we changed the spark plugs. One side(4 plugs) were completely

black. We did not know if they were even throwing a spark. Changed them out.

I put a bottle of tektron(?) in for the fuel. The truck is still running a bit rough when I stop or idle. Maybe I need to give the cleaner a chance. Do I need to look at the other o2 sensors? Any help?

redvett · January 24, 2006

I just experienced the same thing, but it left me stranded on the interstate. It was a bad fuel pump on an 03 Avalance. It caused a misfire code and blinking engine light, lean mixture etc.

I need to rant about it, too. Who the heck designed the fuel system on the avalache?? Its a 3/4 ton with the 8.1l engine. Apparently it has 2 tanks. The front tank has a pump that pumps the fuel to the engine. The rear tank has a pump that pumps the fuel to the front tank as it is being pumped to the engine. Our rear pump failed causing the front tank to run dry and leave us stranded. Seems like they just engineered it with more parts to fail!

<{POST_SNAPBACK}>

The tank system you have is the result of lawsuits on the RV pickups where the tanks were outside the frame rails.Lawsuits are great the cost everybody else more money.