Engine misfires when cold but runs fine after warming up few minutes later?

My 97 SLS used to belong to my grandparents but old age and another car; they gave it to me. They also gave it to me because of this misfire problem it has. It sounds like it runs on 7 cylinders for the first few minutes and runs like garbage if you drive it. There is no knocks in the engine. I took it to autozone to get trouble codes and came back with a random misfire code. The car runs perfect after it is warmed up. I think it just needs a major tuneup. The car sat for 2 months when they brought it back from the dealer for a new water pump. Am I right about this problem? The car only has 82000 and is close for a tuneup.

Update:

No smoke from the exhaust except strong odor of gasoline.

7 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    Probably it just needs a new set of spark plugs.

    Ja.

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  • 1 decade ago

    Usually strong other of fuel and rough idle at cold start up could meanyou have some injectors that are leaking overnight. If it were an ignition problem I believe it would misfire all the time weather cold or hot. Also how is your coolant level? If you seem to be adding coolant more frequently you could also have a minor headgasket leak. Leaking coolant into a cylinder overnigt and you start next morning will also cause a misfire until it burns off the coolant. You may not see smoke at tail pipe because it is a small leak but just enough to cause it to misfire. So take to a shop and have it stay overnight so that they can properly diagnose.

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  • harms
    Lv 4
    3 years ago

    Cold Start Misfire

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  • 1 decade ago

    > trouble codes and came back with a random misfire code. The car

    > runs perfect after it is warmed up. I think it just needs a major tuneup.

    You are very smart. The first place to look when you get misfire is the high voltage ignition section (spark plugs, plug wires, distributors, dist rotors, coils) - basically tune up.

    ===

    > except strong odor of gasoline

    That is because of all the unburnt gasoline being sprayed out the tail pipe. That is almost certainly in need of tune up.

    Good luck...

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  • Eric F
    Lv 6
    1 decade ago

    sounds like it's time for a tune up, AC Delco plugs, wires and a coil pack as well.

    Also a bottle of fuel injector cleaner, anything over $6 is good, Seafoam if you can find it.

    random misfires are caused by things like a bad plug wire, not allowing a plug to fire correctly, or enough, an old plug that can't muster the correct spark, or a dirty fuel injector not spraying fuel into the chamber correctly (this is most common).

    it can also be bad oxygen sensors, vacuum leak, or worse.. leak at the intake manifold.

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  • Anonymous
    6 years ago

    I would also say a minor head gasket problem. Especially about the part where you said it needed a waterpump. I once pressurized a cooling system up to 16 psi overnight and found the head gasket problem fouling out the plug until it burnt off and ran fine.

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  • What's an SLS?

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