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FIXITMAN, Master Technician
Category: Mercedes
Satisfied Customers: 17475
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Random misfire p0300 and p0306 mercedes 2009 c300, 109k very

Customer Question

Random misfire p0300 and p0306 mercedes 2009 c300
JA: How many miles are on the car? Is it a steady misfire? Or random?
Customer: 109k very rough idle
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: swapped coil packs, rand fuel pressure test, compression test, swapped spark plugs
JA: Anything else you think the mechanic should know?
Customer: thats all
Submitted: 1 year ago.
Category: Mercedes
Expert:  FIXITMAN replied 1 year ago.

Hello, my name is***** this misfire continued after these parts were replaced, and if the compression is just fine then you may have a fuel injector issue. Does the misfire occur at all RPM's?

Customer: replied 1 year ago.
Correct, it starts off fine with no rough idle then gets real rough and engine light starts flashing on and off
Expert:  FIXITMAN replied 1 year ago.

Thank you. If you have checked all of this and it is fine and if the connector at the coil is fine then you more than likely have a bad injector.

Customer: replied 1 year ago.
How can I find the bad injector ?
Expert:  FIXITMAN replied 1 year ago.

If you have determined that everything else is fine then you should do an ohm test of the injector and then if that is still not conclusive then it can be removed and professionally flow tested.