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Q: Car misfires even on new plugs.

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I drive a Jetta 4 2004 1.6 Model .All four cylinders does not burn fuel effectively such that the car jerks on gear 1st and 2nd, but after that it pulls . On cleaning or putting in new plugs the car stops vibrating and idle well. about 10 kms then it starts again to misfire with no power as usual. It gives out a black smoke smelling petrol at the back.The top was done with new valve seals on and new gasket but did not change engine oil and oil filter. Timing checked and found to ok. Coil pack and plug cables checked and found to ok. What could be the problem , please help.
My car has a manual transmission.

It sounds as though your car is running too rich and fouling the spark plugs. There may be a problem with a temp sensor that is telling your controller that the engine is cold even after it warms up, so the fuel mixture does not lean out as it should when the engine warms. There are also other possibilities, such as a bad air flow meter or the fuel pressure being too high. Any of these problem should have stored a code in your engine’s controller. Normally this would cause the check engine light to come on, but maybe that light is out. Your car should be scanned for codes to see is there is anything to point to the problem. If you want professional help with this you can contact Your Mechanic to have a technician come out to your home or office to check out your Volkswagen and let you know what it’s going to take to fix it.

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