Engine misfire. Oldsmobile alero?

My wife's 2003 Oldsmobile Alero 2.2 automatic has a misfire I can't solve. I have pulled codes and I get two codes, cylinder 2 misfire or multiple misfires. I have replaced the spark plugs, coil pack and boots, Ignition control module. Fuel injectors, and checked fuses. Still having misfires, the car drives fine once it's moving. But when at a stop in gear the car studders. If I put the car in park or neutral at a stop the car stops studdering and idels fine. I checked and added automatic transmission fluid just to be safe. There was a code that my wife drove with for almost a year for the catalysts converter. But I put a cleaner through the fuel system and the code has not come back. 

TIA.

Update:

Going to do a compression test tomorrow. That totally went over my head. 

Update 2:

Also the car only has 120,000 miles on it. 

Update 3:

Compression is fine like I figured. It's only happening while in Reverse or Drive when at a stop. So im going to have a transmission shop look at it this week and see if that's the issue.

10 Answers

Relevance
  • 1 week ago

    Figured it out. Was the wrong style plugs, even though I been using the recommended style for years. Went with iridium spark plugs and it fixed it right away.

  • REV B
    Lv 7
    3 weeks ago

    Check the coolant level because it might be a blown head gasket. 

  • Jason
    Lv 7
    3 weeks ago

    Disable the injectors and crank the engine and listen for an irregularity if you don't have a compression tester. I use this simple method all the time when I suspect a non-contributing cylinder. 

  • 3 weeks ago

    Take a gasoline sample in a clear jar and after letting it sit for half an hour look for water in the bottom of the jar.

    If you made the mistake of putting any other brand spark plug other then a set of AC Iridium spark plugs go buy the correct spark plugs for your motor.

    Source(s): Mitsubishi Master Tech
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  • Dan
    Lv 4
    3 weeks ago

    Compression test before you spend another dime. If that's good then look for a vacuum leak on that intake runner (#2).

    Low compression on one hole ALWAYS presents as a miss at idle and then disappears at speed because higher piston speed prevents the cylinder from leaking down before compression is lost. Elementary stuff.

    ALWAYS do a compression test when the free checks like swapping injectors, coil packs and plugs doesn't work.

  • 3 weeks ago

    It has to be matched oem injectors, some brands of Injectors are rough like rebuilts, then there's vacuum hose leaks, stuck egr and iac which shows up at idle. Does the misfire go away when revving?

    • Tom3 weeks agoReport

      It's fine when driving. Normally around 2,900rmp for 70mph. Can get up to speed just fine. Only has issues at low idel rpm

  • don r
    Lv 7
    3 weeks ago

    Check the compression. There might be a bad head gasket letting water in the cylinder.

  • bo
    Lv 7
    3 weeks ago

    time for a compression test. sounds like you might have a bad cylinder

  • 3 weeks ago

    maybe you should have a mechanic check it out

    • Tom3 weeks agoReport

      Why would the engine have low compression if it idels and drives fine? Just has issues in gear at a stop. P.s compression is fine

  • Anonymous
    3 weeks ago

    .....................................

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