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Tech501, Auto Service Technician
Category: Car
Satisfied Customers: 747
Experience:  38 years exp, ASE Mastertech with L1 Advanced Engine performance
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97 Chevy Blazer: 4.3L..Im getting OBDII codes p300, P0302, and P0306

Resolved Question:

I have a 97 Chevy Blazer with a 4.3L Vortec engine. I'm getting OBDII codes P0300, P0302, and P0306. Please advise.
Submitted: 12 years ago.
Category: Car
Expert:  Tech501 replied 12 years ago.
 That means your getting multiple misfires from varying cylinders. If it hasn't had a major tune up yet, then I would replace the plugs, ignition wires, distributor cap and rotor.
Customer: replied 12 years ago.
Reply to Tech501's Post: A tune up replacing all those parts was done last summer.
Expert:  Tech501 replied 12 years ago.

 Then something is wrong with some of it. If those are the only codes, then it really has to be a secondary ignition problem. It could be a bad coil or something wrong with the parts already changed. Have someone inspect the inside of the distributor cap and test the coil with an ohmeter. the codes mean

PO300 - Random misfire

PO302 - Misfire on cyl #2

PO306 - Misfire on cyl #6

Customer: replied 12 years ago.
Reply to Tech501's Post: I brought it back to where the tune up was done. Mechanic checked routing of the wires and got them off any metal or other wire. Still got same codes. Brought it back and he pulled a plug from one of the misfiring cylinders. It was slightly blackened, but okay. Also pulled the wire, and the dist. cap. They were okay also. He saw no reason for misfiring. He advised taking it to the dealer since his code reader could not give anymore info.
Expert:  Tech501 replied 12 years ago.
 You just need a better mechanic. The black on the plugs proves it's ignition misfire. You may also want to check the compression in those cylinders. There may not be enough compression for combustion.
Customer: replied 12 years ago.
Reply to Tech501's Post: So you agree that I should take it to a Chevy dealer?
Expert:  Tech501 replied 12 years ago.
 Either that or a more knowledgable independent shop.
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