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Author Topic: non ford gmc sierra p0300 code NvrGoFullRetard CAFords OG Member # 1633 posted                                 posted on other forum. i have a 2003 gmc sierra 6.0 and i was getting a blinking engine light. it was a pre dtc code random misfire cylinder #1. i changed the plugs with the factory ac delco spec plugs and wires. still no change. i then changed the coil pack on cylinder 1 and now i have a p0300 code and runs rough. any input would be appriciated. -------------------- "formally 4.6 eatin gm's" white 97gt n/a 320rwhp/325rwtq 01 sierra rcsb lsx 408 (murdered out) 03 ecsb sierra 6.0 on 22's 2011 Tahoe Posts: 2759 | From: PITTSBURG/FAIRFIELD | Registered: Aug 2002  |  : 5.0 LsX ¯ Member # 10017 posted                              •Faulty spark plugs or wires •Faulty coil (pack) •Faulty oxygen sensor(s) •Faulty fuel injector(s) •Burned exhaust valve •Faulty catalytic converter(s) •Stuck/blocked/leaking EGR valve / passages •Faulty camshaft position sensor •Defective computer just keep going down the list...double check ground wires too -------------------- 91' Notch Posts: 1260 | Registered: May 2010  |  : NvrGoFullRetard CAFords OG Member # 1633 posted                                 I replaced so far, Plugs Wires Coil packs I have an extra set of fuel injectors and o2 sensors i can try. -------------------- "formally 4.6 eatin gm's" white 97gt n/a 320rwhp/325rwtq 01 sierra rcsb lsx 408 (murdered out) 03 ecsb sierra 6.0 on 22's 2011 Tahoe Posts: 2759 | From: PITTSBURG/FAIRFIELD | Registered: Aug 2002  |  : Venomousnotch ¯ Member # 8695 posted                              Code: P0300 Description: Random/multiple cylinder(s) - misfire detected Specification: Spark plug(s), HT lead(s), injector(s), ignition coil(s), low compression, wiring....Have you checked and made sure all your injectors have pulse...The last truck I worked on with this code PO300 ended up being the injectors were not spraying properly.. -------------------- 🏁•2004 MUSTANG SVT COBRA•🏁 "WHEN THE WHINING STARTS,IT MEANS JUSTICE IS ABOUT TO BE SERVED".. Posts: 7604 | From: *NORTHERN*KILLA4NIA* | Registered: Oct 2008  |  : NvrGoFullRetard CAFords OG Member # 1633 posted                                 No i dont havethe proper equipment to check these. But i have extra parts laying around. This weekend i'll try to check it out this werkend -------------------- "formally 4.6 eatin gm's" white 97gt n/a 320rwhp/325rwtq 01 sierra rcsb lsx 408 (murdered out) 03 ecsb sierra 6.0 on 22's 2011 Tahoe Posts: 2759 | From: PITTSBURG/FAIRFIELD | Registered: Aug 2002  |  : Kb69fastback ¯ Member # 13054 posted                              Catalytic converters do this on chevy and gm from 99-07. We do them a lot at my shop. They will throw random misfire codes. No matter how many parts you throw at it, it never changed It always starts with p0301 The cats get clogged and back pressure to the engine and causes the o2 sensors to go crazy Usually cats go bad from faulty o2 sensors as well We use a modis and check for misfire on each cylinder. We Check numbers on o2 sensors and make sure the numbers and switching correctly We also check all the injectors for misfires as well Before you blow anymore money. Go to a muffler shop and just ask for a simple back pressure test. They will put a o2 sensor out and put in a back pressure tester and start the car to see of they're clogged Posts: 90 | From: Roseville ca | Registered: Jul 2013  |  :

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