This one is interesting. I have a 2004 F150 SCrew Lariat. 5.4L. 183000 miles. It idles fine, runs and drives fine, but in Park or Neutral, if I lay into the throttle gently, between about 1000 and 1600 RPM, the motor starts stumbling and misfiring, and almost dies. If it is in drive, and I ease into the throttle, no prob. If it is in park or Neutral, and I lay into the throttle heavy, no problem. My CEL has not come on. I thought bad gas or clogged injector. Ran two bottles of injector cleaner and two tanks of gas through. Still same prob. Any clues?

 

What is the maintenance history on the plugs and coils?

 

Delete: - user is running Champions. NOT spec.

 

clean the maf sensor. when was the last time you changed the fuel filter?

 

I noticed this morning that it does not do it when cold. It will only start to do it once warmed up and out of closed loop. I cleaned the MAF sensor with MAF sensor cleaner, it did not help. Plugs changed at 100000 per manufacturer specs and replaced with champion if I remember correctly. Fuel filter changed at 125000.

 

So - you have had the Champs in there for 83k? Time to change them again. It may also be time for one or more cops.

 

Really?!? Because I replaced the factory Ford crappy plugs with the Champion one piece plugs you delete your post and can not help me? OK. that says a lot. jbrew had suggested that I run the truck in the condition that caused the issue and hold it there until it threw a code. I did so for 15 minutes, and no code thrown. what gets me is that it does not happen when in closed loop (cold) and does not happen in drive.

GLC- yes, I have had the champion platinum plugs in for 83000 miles. According to specs, the platinum plugs are designed to go 100000 miles, and the first ones did with no misfires. I want to find the real reason for the fault rather than just throwing parts at it.

 

Regardless of what the factory specs claim for a lifespan of the plugs, never does it actually mean they all last that long.. You'd be a fool to believe that. It's marketing 101. 83k on ANY plug is questionable. Don't rule them out just because champion claims they are a 100k plug. Some plugs go the life of the truck with no issues, others prematurely fail whenever they feel like it. Plus, condition of the vehicle, fuel grades and such like that all play a role in the life of the plugs. It may not be the issue, it may be... either way, don't rule them out. Preventive maintenance is never a bad thing.

 

Ford is now recommending 60k for 3V plugs. You are using Champions, which DO HAVE a mixed history in these engines, we have reports of people having to change them after only 20k.

Put a new set of plugs in, I don't care what brand, but put something in there. That's not just throwing parts at it, it's good preventative maintenance too.

 

You've gotten your money's worth out of the plugs. Change them. They could also be stressing the coils at this pont.

 

Crap! Wrong thread. That's twice I did that in 5 years.

 

OK, I had planned on doing plugs at 200K, guess I'll bump it up and do plugs and Coils. Unfortunatly, the economy is going to dictate that gets done in about a month. I'll let ya'll know if it helped. jbrew, sorry if I snapped. I was already a little frustrated when I saw that the post had been deleted.

 

Well, I have not replaced the plugs or COP's yet, but lost my tranny yesterday. I still plan on replacing the plugs and COP's after I get my tranny replaced, but just for *****s and grins, is it possible the problem was the tranny going bad and not the plugs in the first place?

 

Doesn't sound like the tranny had anything to do with the original issue to me. Sorry to hear it took a dump. Care to explain what happened?

 

I lost my OD band. Got the truck back yesterday, all new bands and clutches, and rebuilt pump. Of course, the original problem is still there, like I had expected. Plugs next week!