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Dan, Technician
Category: Saturn
Satisfied Customers: 23486
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Saturn L300: 2002 Saturn L300 has P0301 fault code. Service

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2002 Saturn L300 has P0301 fault code.
Service engine soon light came on and flashes during heavy acceleration.
maintenance afterward consisted of Compression check of #1 cylinder within specs, spark plugs are new, fuel injectors have been cleaned.

Light came on again soon after maintenance. Sometime engine runs rough at speed, other times it runs smooth.
Welcome to JustAnswer, my name is XXXXX XXXXX I'm here to help get your problem resolved. This most likely means the coil has failed, remove coil and connect spark plug and wire to number 1 cylinder, it shoudl jump a 30kv gap on spark plug tester, if not replace the coil. Considering what you have done the only other possible problem I see is carboned up valves. You can use seafoam in engine, suck it into engine using vacuum line, let sit over night, then in morning run in low gear at hiogh rpm to burn out any carbon deposits on valve. Let me know if you have questions or if there is anything else I can do to help. Thanks.
Customer: replied 4 years ago.

Would a vacuum leak or a leak in the intake manifold gasket also cause the problem?

That would cause a problem at idle more then under hard acceleration. Vacuum leaks are usaully not noticeable at all under acceleration. The only other thing that comes to mind is the egr valve but that would cause multiple cylinders to misfire, not just cylinder 1. So with everything factored in its still sounding more like a failing coil. Let me know if you have any questions and what outcome is. Thanks.
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