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2004 Chevy Silverado 5.3 Bad Intermittent Misfire

MichaelAllen31

By MichaelAllen31
in Ask A GM Technician

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MichaelAllen31 New Member

MichaelAllen31

Posted
Posted

Hello everyone, I've got an issue that's been bugging me for the past month and a half or so, and would like to get some help figuring it out. This happened out of nowhere, just backing into my spot at school. I felt my truck starting to shake, and smelled a lot of fuel in the exhaust, and i didn't think anything of it. Anyways, i got in my truck, started it up, and i could feel it shaking and lurching at idle at first, then i'd bring it to a stop and it would almost stall.

I got it home, and thought it had sprung a huge exhaust leak somewhere, that wasnt it. It would hesitate only at idle, with check engine light, (Sometimes Blinking) And i was stumped when i'd take it down the road at hard throttle and it wouldnt misfire at all at first. Me and my dad replaced the spark plugs and wires about 2 weeks after this started, didnt fix it, but bank one was extremely black, and bank two almost looked lean. I did the injector test with a screwdriver to listen to the ticking, all seem to be working fine. Now, i just unplugged the battery for about an hour, took it down the road, and it made the same bang that it did to start the whole problem, and it ran perfectly fine for less than an hour afterwards. I parked it, came back out to start it, and the battery was dead (My fault), but got a jumper hooked on it and it started right up, running like trash, that was just tonight. Since we changed the sparkplugs, its been misfiring all the time, and the check engine light has gone away. It used to average about 18 mpg, now maybe 9-10 mpg. The check engine light was blinking the whole time i drove it after the battery died, and im stumped of what may be wrong.

 

I need to have the codes read, but Napa wasnt helpful with that, and our local Autovalue is almost never open, and im not sure if they would read the code for us. Im thinking it might be an o2 sensor on bank one, but cant discern why the truck runs fine sometimes, then runs like garbage other times. It does have a nasty hesitation when taking off from a stop, and it chugs when off the brakes and just idling along. I ran an entire bottle of fuel injector cleaner through the truck with about 1/4 tank, and it didnt seem to help, but it changed what the exhaust smelled like.

Any help would be appreciated as to what might have gone bad, or wrong, thanks in advance! If you need any more info, just let me know.

  • 2 weeks later...
LouieC Enthusiast

LouieC

Posted
Posted

If you have a scanner check the o2's fronts should read, rear should be somewhere around 0 .... what brand of spark plugs did you use ,,, I have seen problems with non oem plugs ei,, champion or autolite where a Ac delco belongs .. I know this is going to make a lot of people say cant happen but as I stated I have seen it first hand .. also did you change the wires?? could one or more be broken.. finally I would look into a good fuel injection cleaning not a tune up in a can but a real injection service

  • 2 weeks later...
MichaelAllen31 New Member

MichaelAllen31

Posted
  • Author
Posted

If you have a scanner check the o2's fronts should read, rear should be somewhere around 0 .... what brand of spark plugs did you use ,,, I have seen problems with non oem plugs ei,, champion or autolite where a Ac delco belongs .. I know this is going to make a lot of people say cant happen but as I stated I have seen it first hand .. also did you change the wires?? could one or more be broken.. finally I would look into a good fuel injection cleaning not a tune up in a can but a real injection service

Hey, I suspected it was an o2 sensor on bank one, i bit the bullet and replaced the upstream and it solved the problem. I diagnosed it by just seeing the color of the sparkplugs, which made no sense to me having them all black on one side. I fixed this about a month ago now. Thanks though!

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