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FIX  IT MAN
FIX IT MAN, Master Technician
Category: Mazda
Satisfied Customers: 17144
Experience:  Automotive Technician Trainer
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I have a P0303 code in a Mazda CX7 2.3L Turbo 2008. The only

Customer Question

I have a P0303 code in a Mazda CX7 2.3L Turbo 2008. The only issue found by mechanic was 155 psi in compression test for cylinder #3. The wet test shows rings or cylinder wall leak. The other 3 cylinders are in 175 psi. No leaks, coils, injectors, coils, spark plugs issues are present as they test it all. Can a 20 psi difference show a misfire code? i think is under specifications (29 psi max dif between cylinders repair manual says). I felt lack of power, backpressure in escape and not so steady idle pointer, moving a little every 5 seconds aprox. The unsteady idle get worst in R gear too.
Submitted: 1 year ago.
Category: Mazda
Customer: replied 1 year ago.
Forget to mention: I hear a pítch noise under the car. Seems comming from some part of tailpipe. Maybe the misfire make more damages or can have a relation? Only code present is P0303.
Expert:  FIX IT MAN replied 1 year ago.

Hello, my name is Bobby. Thank you for the question. Can you tell me how many miles are on the vehicle? Do you feel the misfire or just the lack of power?

Customer: replied 1 year ago.
Hello. 88.600 miles. Just the lack. When car start from cold I can feel a vibration that gets smaller when rpm goes down and car heat engine. Never was like that before. Tailpipe shakes too-more than normal- in that lapse of time.
Expert:  FIX IT MAN replied 1 year ago.

Thank you. Then from what you are saying it sounds like a serious engine issue. Unfortunately it's very common on this engine. You can try an engine flush as it is possible that the rings are sludged but most of the time it is wear.

Customer: replied 1 year ago.
Thanks Bobby, back to the question: Cylinder # ***** 2 and 4: 175 psi. Cylinder # ***** 155 psi. Is that difference enough to cause the P0303 when factory specifications says 29 psi is the max. diference accepted?
Expert:  FIX IT MAN replied 1 year ago.

Though it is considered acceptable that is enough to cause a slight misfire and cause this code.