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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 16889
Experience:  15 years GM master tech
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Have a PO307 error code. Pulled plug on #7 and ceramic

Customer Question

Have a PO307 error code. Pulled plug on #7 and ceramic insulation was blown of and plug was coated in white crust. Changed plug still getting error code.
Think its ignition coil?
Submitted: 2 years ago.
Category: Chevy
Expert:  Gary replied 2 years ago.

is this skipping at idle or is # ***** cylinder dead at idle ?

Customer: replied 2 years ago.
Customer: replied 2 years ago.
I replaced the bad plug, still getting PO307
Expert:  Gary replied 2 years ago.

is there spark at that spark plug ? if so can you remove spark plug # ***** and # ***** and do a compression test and see if # ***** and # ***** cylinders have the same compression of over 125 PSI ?

Customer: replied 2 years ago.
If compression is at 125 on 5 and 7 then you feel its the coil?
Expert:  Gary replied 2 years ago.

if the compression is the same as # ***** then this issue is a coil or a fuel injector or the coil and fuel injector not being told to fire

you can switch # ***** coil with # ***** coil and see if the skip moves to # ***** if it does then it is the coil

if the compression in #*****lower or even 0 then there is a valve train failure or possible piston issue which a leak down test needs to be done and the valve cover removed for further inspection

Customer: replied 2 years ago.
OK, good idea and thank you. Happy motoring.
Expert:  Gary replied 2 years ago.


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