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FIX IT MAN, Master Technician
Category: Mazda
Satisfied Customers: 17475
Experience:  Automotive Technician Trainer
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Ew, we have a 2007 cx-7 with a random misfire code p0300.

Customer Question

Hi Drew, we have a 2007 cx-7 with a random misfire code p0300. The car runs rough when its warmed up. Any idea what this could be?
Submitted: 1 year ago.
Category: Mazda
Expert:  FIX IT MAN replied 1 year ago.

Hello, my name is***** for the question. Can you tell me how many miles are on the vehicle? Is there any engine noise when this occurs?

Customer: replied 1 year ago.
The vehicle has 78927 miles and the engine does not make a strange noise when it misfires, but the rpm go all the way down and it shakes, then it works fine for an unspecified time, then the rpm go down again and it does not want to rev.
Expert:  FIX IT MAN replied 1 year ago.

Thank you. Does this only happen at idle?

Customer: replied 1 year ago.
No, it happens whilst driving and at idle.
Expert:  FIX IT MAN replied 1 year ago.

Thank you. Typically this is something simple such as dirty injectors or worn spark plugs or a failing ignition coil. It can also be weak fuel pressure. Has the vehicle ever had a tune up?

Customer: replied 1 year ago.
The spark plugs are new , the injectors clean, and the coils are fine. The vehicle is serviced regularily.
Customer: replied 1 year ago.
Define tune up
Customer: replied 1 year ago.
Do you not have any other ideas?
This has been of no help up to now.
Expert:  FIX IT MAN replied 1 year ago.

Sorry for the delay in getting back with you. I was unavailable earlier. To answer your question, it sounds like to may have a valve issue or possible a sensor reading improperly. A worn timing chain can also cause this. Has a compression test been done on the engine? If not you need to do one hot and cold to see if there is low compression on any of the cylinders.