Misfire P0300 HELP

Asked by Jun 26, 2016 at 12:27 AM about the 2005 GMC Yukon SLE

Question type: Maintenance & Repair

So I got the P0300 code. I thought it was just a bad
coil so I replaced. Wasn't it. Did a tune up. Never
fixed it. So I pulled valve covers found #5 cyl to
have a bent push tube. Checked all of the others.
Number the only one. Replaced tried again still the
same. So I've replaced timing chain oil pump the
oil pick up o-ring. Map senors. At high idle it runs
fine. It won't stay running at all. I even replaced the
injector on #5 to.  I'm lost not sure we're to go or
what to do.

2 Answers

82,115

You may have some issues with the valve train, vacuum leaks need to be checked for, but why would a push rod be bent in the first place would be the question. P0300 CHEVROLET - Cylinder Misfire Detected Random Cylinders- Possible causes - Faulty spark plug (s) - Faulty ignition coil (s) - Clogged or faulty fuel injector (s) - Intake air leak - Fuel injectors harness is open or shorted - Fuel Injectors circuit poor electrical connection - Ignition coils harness is open or shorted - Ignition coils circuit poor electrical connection - Insufficient cylinders compression - Incorrect fuel pressure- The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem....

2 people found this helpful.

I changed sparkpug and wires car ran ok for a few weeks but now po 300 comes up. On my 2004 yukon

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