P0300 - Random Cylinder Misfire

[arpster]

My venture started missing pretty badly activating the SES light and giving code P0302, #2 cylinder misfire, so to start, I changed all the plugs and wires as they were past due anyway. However, the misfire continued and was getting worse and under a load, the SES light would blink. I got the codes read again and it showed P0300. I removed the plug wires from the coil pack feeding the #2 and #5 cylinders and noticed the terminal for the #5 was corroded pretty badly. The guy at the parts store had printed out a table that showed the primary and secondary resistance values for the pack, so using a multimeter, I checked them. The primary was good but the secondary was virtually open instead of the 6k-11k shown in the table. I checked another of the coil packs and the resistance readings were good. So, $27 and some change later for a new coil pack and it runs like new again.

The primary reading is taken from the bottom where it snaps onto the Ignition Control Module. There should be .2-.7 ohms resistance across the input terminals and then the secondary is taken across the output terminals for the plug wires, there should be 6k-11kohms resistance.

I hope this helps someone.

[danielsatur]

What's all in common with all cylinders?

Air - New air filter, replaced MAF/IACT sensors, new upstream HO2 sensor, and clean the throttle body.

Fuel - New fuel filter, fuel pressure test.

Exhaust - A plugged catalytic converter, can cause random misfires.

Keep all replacement parts for spare parts, except for the filters.


Also, see Similar Threads at the bottom of yours.

[lesterl]

He was having issue with 2 cylinders (common component was the coil, it was bad, he replaced, and posted procedure to test so someone else can benefit.)