Hi guys, new to the site, love it already. I have a 2000 F150 4.6V8 with 97k yesterday out of the blue it started misfireing from about 1000 to 1800RPMs. but only when it was under a load, in park, reving it is fine, then when i ran it for a while it got worse and would misfire when it was idling, or atleast it feels like a misfire. I searhed the site and found others with what sounded like the same problem, so i did what some of them said, I cleaned the maf with a can of air, reset the pcm, and disconnected the cops one by one, but when i disconnect any of the cops it runs real bad. could one of my plugs be bad? Im confused because it only does it under load unless the motor is real hot. any help would be a life (and wallet) saver.
thanks guys

 

take it to Auto Zone and see if you have a code registered in the computer. is the "service engie" light come on? eventually it will come on if you have a miss, then they will read the code and verify problem.

 

stylintoys:
Chances are really good that you have a coil pack failure. The engine on my Screw acted the same way earlier this year. Took it to the dealer and they had it fixed within a day. #5 coil pack. Good luck. Mert

 

Welcome to the forum stylintoys

How many miles on the spark plugs?

 

Well i put new autolite plugs in, and changed 3 bootes that were cracked and it ran great for 10 miles, now its happening again and gets worse the warmer the motor gets, im not getting any codes, it took it to autozone, and nothing came up, no check engine light. can a coil pack go bad and still operate at low rpms?

 

My 98 F150 V6 did the same thing out of the blue @150K miles. Code reader said 'cylinder #1 misfire'. While changing the plugs and wires, I found the #5 plug so loose that I could wiggle it with my fingers. Since the new plugs and wires, it hasn't given me any more problems. So I don't know if the loose plug or the bad plugs/wires was the issue.

 

i had a miss for a wweek and no codes. finally it got bad enough that it registered and that told me what COP to look at. I had Auto Zone check a couple times and nothing. "check engine" light came on a week later and i took it in and they had the code then. maybe play with the throttle some and try to make it miss a little heavier so it will register a code???

 

thanks for the help guys, im still tryin to get a cel

 

Autolite plugs don't work well. I work for a Ford dealer, and if I had a nickel for every time somebody brought a vehicle in that was bucking or missing and recommended them plugs and/or wires and they said "but I just changed them" I'd be a rich man. At that point, I know they didn't use Motorcraft. I'm not just trying to sell a product, because I'm sure nobody on this board would buy from my dealership anyway... Just trying to shed a little light on the situation.

 

I agree with ArkieRebel as I have been through this issue myself. USE ONLY MOTORCRAFT PLUGS. I'm saying that and I don't work at a dealer.

 

What is it with the other plugs that cause a problem? Is there some radical difference with the Motorcraft plugs?