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RE: P0300, P0302, P0306 OBDII codes.

Sent to Car Experts May 08, 2005 3:51 p.m.

I have a 97 Chevy Blazer with a 4.3L Vortec engine. I'm getting OBDII codes P0300, P0302, and P0306. Please advise.

Customer (name blocked for privacy)

Status: Closed Value: $10

Answer
May 08, 2005 3:56 p.m. (5 minutes and 8 seconds later)

REPLIED

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.

Tech501 -- Auto Service Technician -- 96% Positive Feedback on 739 Car Accepts
38 years exp, ASE Mastertech with L1 Advanced Engine performance

Reply to Tech501
Sent May 08, 2005 3:58 p.m. (2 minutes and 10 seconds later)

A tune up replacing all those parts was done last summer.

Customer (name blocked for privacy)

Answer
May 08, 2005 4:04 p.m. (6 minutes and 3 seconds later)

REPLIED

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

Tech501 -- Auto Service Technician -- 96% Positive Feedback on 739 Car Accepts
38 years exp, ASE Mastertech with L1 Advanced Engine performance

Reply to Tech501
Sent May 08, 2005 5:44 p.m. (1 hour and 39 minutes later)

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.

Customer (name blocked for privacy)

Answer
May 08, 2005 5:50 p.m. (6 minutes and 2 seconds later)

REPLIED

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.

Tech501 -- Auto Service Technician -- 96% Positive Feedback on 739 Car Accepts
38 years exp, ASE Mastertech with L1 Advanced Engine performance

Reply to Tech501
Sent May 08, 2005 5:57 p.m. (7 minutes and 29 seconds later)

So you agree that I should take it to a Chevy dealer?

Customer (name blocked for privacy)

Answer
May 08, 2005 6:00 p.m. (2 minutes and 37 seconds later)

ACCEPTED

Either that or a more knowledgable independent shop.

Tech501 -- Auto Service Technician -- 96% Positive Feedback on 739 Car Accepts
38 years exp, ASE Mastertech with L1 Advanced Engine performance

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