Q: Vehicle misfiring and I don't know why

asked by on January 21, 2016

It feels like my vehicle engine is misfiring, but the Check Engine light is not coming on. The RPMs also jump up and down. I have changed the fuel pump, fuel filter, spark plugs, plug wires PVC valve, and run a fuel additive called HEET through it. I also changed the thermostat for an unrelated problem, and inspected the fuel rail. I do not know what to do next and need professional help.

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