2001 4.2 Running Rough
 

I have a 01 F150 with a 4.2L V6 with 193,000 miles. Last week while driving home from work, I slowed to turn onto another road and when I started accelerating going through the gears it started shuddering and running really rough like it had a miss. The check engine light began to flash until I let off the gas. I limped it home and put my code reader on it. It gave me a P0304 and P0174 which of course is cylinder 4 misfire and bank 2 lean. Now I put new plug wires on it over a year ago and a new coil pack last August because it had a miss when in a hard pull. The coil fixed it and it's run great since except for having to replace the isolator bolts and gaskets in the plenum. So, I put another set of platinum plugs in it yesterday which would be the second set I have put in it. No improvement so I went back to O'reilly's and exchanged the Borg Warner coil for a new one and I thought sure it would fix it but it didn't. It still runs rough and I still get a P0304 code. Could a plug wire have already gone bad or do I possibly have a bad injector? They have never been replaced. When I pulled the old spark plugs out the #4 plug looked different than all the rest. Anybody have the same experience with theirs?

Maybe swap the #4 injector with say #1 and see if the miss follows.

Also check the PCV system real good for bad hoses, and go over ALL the vac hoses including the brake booster hose.

By the way, I checked the resistance of the #4 injector and it was 12.9 ohms which is below what my Haynes book says. They say it it's supposed to be 13.5 to 19 ohms. I checked a couple more and they were 13.1 ohms. But I also checked the old coil pack secondary resistance and go no reading at all so it may be the test meter. I also wonder about bad gas.

With the motor running at idle I can put my finger and thumb on the #5 and #6 injectors and I can feel them clicking so they are working. But, when I feel of the #4 injector I can't feel anything at all. I don't have an engine stethoscope to listen to them as is said by Haynes but you can feel them working. I guess I'll get a new injector tomorrow. I may have just got clogged up.

Before you start throwing parts you could switch it with a good one and see what happens.

Also you might try un-plugging the suspect and re-connect it to see if it's just a plug that wiggled loose.

Hey any tricks to changing injectors without having to buy new upper gaskets?