wjalex4

Have a recently acquired 2003 GT w/4.6L. Automatic. Has an occasional misfire or maybe fuel delivery issue. You can feel it while driving. No CEL codes.

I found a post about the coil pack electrical connectors coming loose. Since this engine has about 255K on it, I checked each one, and even ziptied them in place so they are nice and tight. The issue is still there now and then.

Sometimes it will run fine all week, then the issue occurs a few days, then it's gone again. Today I will replace the fuel filter, but anyone have any other thoughts or perhaps experience with such an intermittent issue?

Thanks so much - Walter

dawson1112

Upstream 02 sensors dont always generate a code, but they can cause some strange issues when they fail. Both of my 00 gts had to have 02s replaced, even though no codes were displayed or stored, the cars would misfire for no reason, then run good for a bit, then misfire out of no where. Changing the 2 front 02s solved it on both cars.

wjalex4

That's a great idea Dawson1112. Thank you - if this fuel filter does not fix it, I will replace those two upstream O2 sensors.