bvfd_gordo Posted November 23, 2009 Report Share Posted November 23, 2009 I have a 2002 Gmc Sierra 1500 with a 4.8 liter V8. In the last couple of days my truck's "service engine soon light" came on and the truck started running fair to crap with-in a day or so. I did a code scan error codes that came up were P0101 and P0300. I change fuel filter, change spark plugs, cleaned the Mass air flow sensor and ran a bottle of Lucas injector cleaner through it. The P0101 code has cleared but now the P0300 code is still there. All I can find on the P0300 code is Random/multiple cylinder misfires. I need help. Quote Link to comment Share on other sites More sharing options...
MrX Posted November 23, 2009 Report Share Posted November 23, 2009 I have a 2002 Gmc Sierra 1500 with a 4.8 liter V8. In the last couple of days my truck's "service engine soon light" came on and the truck started running fair to crap with-in a day or so. I did a code scan error codes that came up were P0101 and P0300. I change fuel filter, change spark plugs, cleaned the Mass air flow sensor and ran a bottle of Lucas injector cleaner through it. The P0101 code has cleared but now the P0300 code is still there. All I can find on the P0300 code is Random/multiple cylinder misfires. I need help. Your mass air flow sensor is not reading the air flow with in spec. If the (MAF) is off by .5 Hertz it can make the truck run bad. and wont throw a check engine light. you need to have the wave pattern check by some body who knows how. Quote Link to comment Share on other sites More sharing options...
bvfd_gordo Posted November 23, 2009 Author Report Share Posted November 23, 2009 I have a 2002 Gmc Sierra 1500 with a 4.8 liter V8. In the last couple of days my truck's "service engine soon light" came on and the truck started running fair to crap with-in a day or so. I did a code scan error codes that came up were P0101 and P0300. I change fuel filter, change spark plugs, cleaned the Mass air flow sensor and ran a bottle of Lucas injector cleaner through it. The P0101 code has cleared but now the P0300 code is still there. All I can find on the P0300 code is Random/multiple cylinder misfires. I need help. Your mass air flow sensor is not reading the air flow with in spec. If the (MAF) is off by .5 Hertz it can make the truck run bad. and wont throw a check engine light. you need to have the wave pattern check by some body who knows how. I swamped the MAF with another truck did not change anything at all. Quote Link to comment Share on other sites More sharing options...
MrX Posted November 23, 2009 Report Share Posted November 23, 2009 check fuel pressure it should be at 55 to 65 psi. Check for plug exhaust by taking out front O2 sensor and drive the truck to see if it got any better. Quote Link to comment Share on other sites More sharing options...
bvfd_gordo Posted November 24, 2009 Author Report Share Posted November 24, 2009 UPDATE Clogged catalytic converter was the problem. Quote Link to comment Share on other sites More sharing options...
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