Random Misfire!

[ToyTech]

2001 Sierra 2500HD 6.0 Litre with 350,000Kms, Random Misfire code P0300. (No other codes registering) The engine stumbles and the check engine light flashes at idle. It is fine at over 2300 RPM's. Cylinders 2 & 6 are misfireing the most. All new plugs, wires, fuel filter and EGR in the last week.

Is this a converter problem on the one side or an 02 sensor failing

Any thoughts?

[2500ak]

Never drive a truck that has a flashing CEL.

[bobcat5544]

Your problem is to much fuel. Any time the check engine light flashes it means to much fuel is getting dumped into the exhaust.

 

Does the scanner show how many time each cylinder is misfiring per cycle at idle and higher rpms

[ToyTech]

Thanks! ...for the effort Jonesy55. You are right, it was too much fuel. I changed the upstream O2 sensor this morning and the truck is back to normal.

Talk to you later!