Offroad Trailblazers and Envoys

PO300 Error [solved]

Something not working right?

by med71 » Sat Apr 20, 2019 5:36 pm

I have the random misfire code, PO300...sigh. My 2003 Envoy only has this code. One strange thing is that it won't rev past 3,000-3,200 RPMs. When the car is cold and started, it runs smooth but will not rev past 3,000. When the car reaches operating temperature it runs rough, missing, and will not rev past 3,000.

Here is what I've done:
1. New plugs and coils on all six (was planning on doing this anyway). The old plugs looked good and they all looked the same.
2. New fuel filter. Fuel pressure check showed 60psi at idle and under load with no fluctuation on the gauge.
3. I still have about half of a tank of fuel, and I haven't drained it. I did put heat in it just in case.
4. The gas cap looks weathered, going to order a new one.
5. Verified all wires and vacuum lines.
Last edited by med71 on Sun Apr 21, 2019 10:25 am, edited 1 time in total.
med71
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Name: Mark
Vehicle Year: 2003
Vehicle: GMC Envoy
DriveTrain: 4WD

by Diacom » Sat Apr 20, 2019 10:03 pm

Diacom
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Name: Noel
Vehicle Year: 2003
Vehicle: Chevrolet TrailBlazer
DriveTrain: 4WD w/ Aftermarket Locker

by med71 » Sun Apr 21, 2019 10:27 am

I got this fixed last night. I went back through the coils, and I noticed that the purple insert on the #6 connector was inside one of my old coils. When I put the connector on the #6 coil, it bent the pins.
med71
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Posts: 8
Joined: Wed May 09, 2018 7:27 pm
Name: Mark
Vehicle Year: 2003
Vehicle: GMC Envoy
DriveTrain: 4WD

by Flyingfischer5 » Sun Apr 21, 2019 9:45 pm

Awesome! Glad it was something quick and easy! Good job!
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Vehicle Year: 2004
Vehicle: Chevrolet TrailBlazer
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