My work van is an 02 with the 5.4 in it. When the truck had 20,000 miles on it, one day it just started missing, like a cylinder wasn't firing at all. Shut it off... fired it back up, and it was fine. Hadn't had a single problem with it, and now at 60,000 miles, it misses when it's warm.

The thing is, it only misses at a low RPM when you are accelerating. I'd say around and below 1700 RPM.

We took it in and had the plugs changed and 2 coil packs replaced (The PCM was saying cylinder number 6 and 4 had noted a misfire.) It ran fine for about a week after that, and now it's missing again. By the way, there has been no Service Engine light whatsoever. It comes on when you turn the key on, but never on while running.

I was reading around and saw that maybe the MAF is dirty. Is it in the air tube near the air filter box? If so I don't remember seeing it and will look harder!

Thanks a bunch!

 

It is in the air filter housing on the engine side. If you look thru the tube, you should see it. Just spray the two filiments with brake parts cleaner or electrical contact cleaner. Do not touch them, they break very easy.
You might try a scan anyway, it may have a stored code without turning on the light.
Also, check the PCV hose assembly elbows, they have been known to crack and cause a vacuum leak.

 

Thanks for the reply Jimmy. I went out this morning, and sprayed what I believe was the MAF sensor (Located inside the airbox.... had 2 wires with a resistor in between, and another set of wires inside the sensor) down with electrical contact cleaner. I did spray off a small small blade of grass off of one of the wires, thinking that was the problem. Well I drove it today and still the same problem.

It idles fine, and runs at high RPM's just fine, but only if you're more that midway into the throttle. I almost wonder if it is a throttle position sensor, seeing how my boss doesn't know how to keep his foot steady in the pedal, and he drove the van before I did. He's one of those drivers who keeps a steady speed by giving it half throttle, and then lets completely off every 5 seconds.

What makes me rule out the throttle position sensor is the fact that whenever you are giving it steady throttle on flat terrain, it doesn't miss a lick. If you start to climb a hill and it stays in OD with the torque converter locked up 100%, thats when it misses, and also during slow acceleration.

Before we had the plugs changed, it missed consistantly when it was warm on one cylinder. Once it was warm, I would put the tranny in 2, hold the brake and give it gas, and it was a consistant miss. That went away whenever we changed the plugs.

I looked at the elbows also leading to the PCV hoses, and saw no problems. Wouldn't that cause a problem at idle also? I have honestly thought about swapping computers from our 03 which has 58,000 problem-free miles on it and seeing how it runs then, but I'm not sure if they will swap out. Any ideas?

 

Had a similar issue, once in a while and for little reason one cylinder would shut down. It did it once, then went 2k miles with out, then again and another 500 miles with out.

I changed plugs and coils, and the problem seems to be cured. Pull your coils and look for discoloration around the boots. While you have them off, refill the cavities with dielectric gel.

 

Twice now on non Ford vechicles I have gotten the clyinder miss fire code and both times the real fix was to clean the fuel injectors. Just a though.