Why do I have a P0300 code?

Asked by Darla Jul 08, 2015 at 08:36 AM about the 2001 Chevrolet Blazer LS 4-Door RWD

Question type: Maintenance & Repair

New engine installed last week. This is the second new engine in 18 months. The first one failed and thankfully was under warrenty. I picked it up Thursday and it runs better than it has in years. Problem is, I have a SES light on. The codes were P0300 random misfire and P0135 O2 sensor. We changed the O2 sensor and took it back to the shop for the P0300. They can not find the problem. The latest is they want to pull the engine away from the torque converter/transmission to see if they are bad and throwing the engine off balance. Can that be possible?

4 Answers
210

Tim answered 9 years ago

Have they changed the spark plugs or checked the ignition coils? This is most often the cause of misfire besides bad computer signal.

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Darla answered 9 years ago

They put new plugs and wires. I don't think they checked much of anything. My main question is can the torque converter/transmission cause a false P0300 code? I think they are tired of working on my vehicle since most of the work has been warrenty work and they are not really making any money.

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Paul answered 9 years ago

Did they check for proper fuel pressure. I would also have them look at the crank and camshaft sensor to see if they are aligned correctly.

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Michael answered 9 years ago

The multi misfire can also happen if you have clogged injectors. Happened to me and I ran some fuel injector cleaner through and it took care of the issue. Hope this helps.

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