'01 Silverado - Occasional engine miss

Discussion in 'GM Powertrain' started by rum river, May 12, 2009.

  1. rum river

    rum river New Member

    I've posted this in the Fuel & Peformance area too.

    This is an HD2500 Crew Cab long box, 6.0 litre gas. I'm the only owner, it has about 75,000 miles.

    'Service Engine' light was flashing, mechanic said the error was #1 cylinder having misfired 35,000 times. I replaced the plug wires with an AC Delco set (I have the Delphi system). I still get the 'Service Engine' light after only 5 minutes at 70 mph. At 65 mph or less there is no light. Took it back to the mechanic for another read. I no longer have an error on #1 cylinder. I now have a misfire error on cylinders #5 and #6. This error is only occasional though. The mechanic had to drive the truck to read the error (the first time he was able to read the error with the truck just idling), and then it would read 1 or 2 misfires only, not the 35,000 I had before I replaced the wires. He did not drive it at 70 mph, so the 'Service Engine' light never even came on for him. The plugs have less than 5,000 miles on them.

    Is it possible this is injector related? The mechanic replaced the fuel filter the same time the new plugs went in, and he said it was pretty bad. I checked my maintenance records, and my gas tank has never seen any injector cleaner.

    You can't even feel the miss, if it weren't for the 'Service Engine' light, I wouldn't even know the truck thinks anything is wrong.

    Anybody experience this before?

    This looks like a great website, glad I found it.

    Rum River
  2. Z71_guy

    Z71_guy Epic Member 5+ Years 1000 Posts

    welcome to the site, it could be injector related, but i wouldn't bet on it misfires are one of those things that take time to diag. when they jump around like that
  3. vncj96

    vncj96 Epic Member 5+ Years 1000 Posts

    Maybe not getting enough power to the plug:neutral:
  4. rum river

    rum river New Member

    I had the fuel system cleaned last night.

    Throttle body swabbed out, cleaner injected through the PCV hose, and cleaner added to the fuel tank.
    Heading to the mechanic again after work to read/reset the current messages. This time I'm going to drive and make sure we do at least 70 mph to see if the messages change.

    I'm heading out this weekend on an ATV trip (over 400 miles round trip). I'm going to put up with the flashing light and see if the injector cleaner makes a difference or not.

    The next step (based on today's readings) will be to swap coil from an erroring cylinder to a non-erroring cylinder and see if the message moves with the coil.

    I'd like to do this before this weekend's trip, but I don't have the time.

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