Car is misfiring. What do I do?

My car started to misfire so I went and replaced the spark plugs thinking that would fix it. It didn't. Now I don't know what it is. I read that it could be a bad head gasket but I'm not too sure. The car has been burning a lot of oil and coolant lately so I'm thinking it is the head gasket. Please help. I ordered a new head gasket, valve cover gasket, and manifold gasket to replace but I just wanted to make sure that was the problem. Thanks

5 Answers

  • 1 year ago

    If you suspect bad head gaskets i would buy a combustion leak tester first, and then confirm that the head gaskets are bad first. Bad head gaskets also make a lot of white smoke out of the exhaust as well. Please make sure the head gaskets are bad before you replace them. If it's not the head gaskets it could be a lot of things. First thing i would ask is if the misfire is random or constant? is it specific to a single cylinder or is it random on all cylinders? What is the make/model/year of the car. are there any codes? But, for now---> First I would check the spark plugs(which you replaced), wires, and coil pack/distributor. If you have a coil-on-plug ignition system, swap the coil from the cylinder that’s misfiring with a coil from a different cylinder. if the misfire follows that coil, replace it. If the ignition system uses "wasted spark system" then the misfires should appear in the two cylinders powered by the same coil pack. If you still suspect ignition, then replace the wires, and buy a spark tester. If it's not any of these, then it's probably related to fuel, or compression. I would probably check compression first.

    Please comment if you need any more information.

  • 1 year ago

    Quit messing around playing mechanic.

    You have no clue what you're doing and bound to bend all your valves if you're dumb enough to take the motor a part with no experience! You haven't even enough brains to tell us the year, make and motor size so we could try to help you.

    Source(s): Mitsubishi Master Tech
  • Anonymous
    1 year ago

    1. Compression test guage buy or rent, verify gaskets, google how to test, burning oil, could be tead read, you dont need us.

  • 1 year ago

    It’s always best to diagnose faults before chucking parts at the problem hoping to get lucky.

    So first get a coolant test: any competent repair shop can take a tiny sample of coolant and use a testing kit to check for combustion products. If present then the head gasket has failed.

    It’s then wise to get a two compression tests done on each cylinder. First one is “dry”, second is “wet” (a little squirt of engine oil into the plug hole before the test). If the wet test gives much higher reading than the dry one then the piston rings are worn/broken so not sealing. That could suggest it’s cheaper to fit an entire reclaimed engine or time to junk the car. If the tests show low compression and no change for the wet one then the problem is usually leaky cylinder head valves so you’d then expect to add a cylinder head overhaul to replacing the gasket. But never overhaul a cylinder head without first getting it crack-tested: again, any competent repair shop will have the necessary test kit.

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  • 1 year ago

    If you are loosing coolant with no apparent leak you most likely do have a blown head gasket or cracked head. A compression test will verify this. A miss can also be caused by a bad injector, burnt valve, bad plug wire, bad coil if coil on plug ignition, and broken rings.

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