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Q: Trouble code P0303 - 2002 Dodge Ram 1500

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I'm getting a P0303 code and I replaced the ignition coil, spark plug and fuel injector to try and curve the issue but it still misfires. And when I'm driving on the interstate and have it set in cruise control the misfire monitor does not indicate a misfire. So my question is what could still be causing the misfire in cylinder 3?

My car has 224000 miles.
My car has an automatic transmission.

A: Hello. If there is no misfire on the highwa...

Hello. If there is no misfire on the highway then you more than likely either have a vacuum leak that is causing this or more commonly a valve seat that is failing.

I usually do a compression test first. This would tell me if there is an internal failure in the engine. Most of the time this is the problem. If the compression is fine then I would do a vacuum leak test to see if there is a leak in the intake manifold gasket.

If you need to have this misfire inspected, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair this.

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