2001 4.2l with 140k miles. I recently had my check engine light come on and noticed that the truck seemed to have lack of power and was popping under light acceleration and figured it was plugs or wires. I had codes read and it gave cylinder 3 misfire and 2 other generic ignition fault codes. I replaced plugs and wires and it seemed to run like new for a day or two. The problem came back and will sometimes mis and pop and other times it will just start shaking like a cylinder is not firing. I checked the ohm levels on the coil pack and they were within range. I read that even if they are in range it can still be bad and that heat can make a bad coil worse. The problem seems to be worse when its hotter outside. Please help!

 

I hope you used Motorcraft plugs and wires and dielectric grease in the boots at both ends. Next step is replace the coil pack.

What were the exact "P" numbers of the codes?

 

did all the above, the one code I remember was like p 303 which was cylinder 3 misfire I accidently threw the other codes away. I can go get them read again tomorrow. Do you think the coil could be bad even though the ohms were within range?

 

ok I found the codes from autozone p01071,p01074, and p0303...from what I have read on my own it says that when bank 1 and 2 are set off together it could me the MAF.

 

I've had that problem and went first to replacing my plugs. The left side was normally burnt but when I pulled the plugs from the passenger side row of cylinders I found 2 Bosch plugs gapped wayy beyond what they are supposed to be and it cleared up my misfiring/kicking.

Next step would be wires then coil pack and maybe vacuum?

 

171 and 174 means it's running lean, usually a vacuum leak. If you have an oiled type air filter, that can foul the MAF, if this is the case, clean the MAF and put a dry air filter in it.

Yes, the coil could be bad, but you gotta fix the lean codes first. Even strong plugs/wires/coils can misfire if you are running lean.

 

90% of the time.....
P0171 / P0174 is caused by a vacuum leak. I have repaired these codes on many vehicles, both on V8 & V6. Just a cpl of days ago I fixed my step-sons 4.0L Ranger with those codes. Read through the thread I started a couple of days ago and it will point you to what I found to fix it. He was sucking in so much extra air that it kicked out a "random misfire code" as well. I repaired the vacuum leak and his truck runs great again with no CEL coming back on.
The MAF could be one of the problems so just clean it really well with CRC Electronics cleaner. Spray the sensor really well with a new can. The new can will have plenty of pressure to wash the sensor off.

Good luck with it.

 

GLC is 100% right on this. The Ranger I just repaired for these codes had new. plugs, wires, airfilter, & fuel filter put in a month ago. When the rubber, 90 degree elbow in the front of the engine blew a hole threw it, it ran so bad at idle and driving, you wouldn't have known that I just put a tune-up on the truck.

 

Thanks everyone!

 

GLC is right about the lean problem fouling plugs.... but the 4.2 is notorious for throwing the lean codes.... mine has been on for 3 yrs now and runs perfect though

The misfire is more than likely the coil pack... I went through the exact same as you at 145,000.... the coil pack tested fine but still had misfire on cylinder #1 replaced the coil pack and all better

Back to the lean codes....youve got options...
#1--live with it
#2-- chase vacuum leaks
#3--most likely cause.. http://sites.google.com/site/fordf15...p0174fix/Home/

 

I agree about the 4.2 always throwing the lean code. I've had lean codes for both banks for the past two years. I had the engine replaced with a remanufactured shortblock 70k miles ago and I'm still throwing the codes. I've checked for vacuum leaks all over the place and everything runs fine. It's more than likely the link that Paul posted.