My '01 4.2l with 88K on it is starting to act a bit sluggish when it's wet outside. I have changed the plugs and wires (which it definitely needed), but it still misses a bit if it's wet out. Doesn't throw any codes....any ideas? Coil pack?

 

Someone please help! I am having the exact same problem with my 01 f150 4.2 with 100,000 miles on it.

 

hi, i seem to remember reading on the forum about loose nuts holding the main cables in the fuse box that is on the bulkhead ,passenger side, causing problems with computor etc.
it may be worth checking before buying a new coil pack.

 

Hmm... Can you show me a picture of which exact nuts you are talking about? I tightened a couple of bolts that, weren't really loose but, could be tightened. It had no effect. When it is dry it will run a little rough until I get into the higher RPM range. Might that be a coil?

 

I dont think it's a coil.
This intermittent miss is a problem with the 4.2's, I see it on the 97-2003 forum.
You get all kinds of suggestions, but the closest anybody's ever come to an answer was a guy who had the code reader hooked up to his laptop, and when the "miss' occurred, he was able to latch a Code that read something about "Missing first Pulse" .....
Now what does that mean? How does it apply? What does it apply to?

None of those questions are answerd.

My humble opinion is:
When the Computer goes from Closed loop (steady state engine Rpm and load. As in Cruise control on, pretty level terrain) ....
to the Open Loop, meaning the terriain just steepend, the load increased, the Vacuam control on the CC moved the TPS to apply more fuel, the Computer went to Open loop.

There, it began to look at all the sensors in turn, in preperation for applying more fuel.

When the Computer satisfies itself, we need more fuel, it starts the process of opening the throttle, increasing the ignition timing etc etc....(I dont know what all it really does) but as this begins, it misses the first "Ignition timing sequence pulse" and with that, all six will not fire for one cycle.
That's the "Miss" or "Bonking" we feel before the truck even begins to accelerate for the Hill.

So, my opinion of the mysterous "miss" is that one or more of the Sensors in the Cycle is either slow to input, or just a little below (or above) what the Computer is expecting.
However without a code to give a hint, you'd never know what sensor to look at.

If I'm right....this problem could be a Bad ground, a corroded or dirty wire connection, an actual bad or dirty sensor, or something even more benign as in a fuel filter or air filter.

I changed my Plugs, Air filter, fuel filter and cleaned that little sensor down in the air cleaner.
I pulled both battery cables and cleand the terminals.
None of that changed the problem.

I see in a post down in the electrical threads that a guy changed his negative battery cable for $9. and that seemd to solve a similar problem for him.
That's next for me.

So now, behind all my blabber, what do the guys with the training on the Ford Electronics think?

 

Mine did throw a code after it was ran through a car was and I took it to advance and they said it was a miss fire. I replaced the plugs and #3 had some black residue on it. Also, it runs rough at idle. Would this be caused by the same problem you described above?

 

Some good guesses so far. I can't hazard a good guess as to what the problem might be, but maybe you can find it.
Could you pick a day when it is very dry and all is working fine, and try to create the problem by finding a particular area bothered by moisture?

You could use one of those mist spray bottles to mist small particular areas and/or components to hopefully find a problem area. Might have to turn the engine off to isolate some areas for mist spraying (to avoid the fan blowing the mist all over) and then restart the engine.

Worth trying I guess.

 

Might be worth a try. Can't do it today, the temp is 96 and the heat index is 105-110. The humidity is probably enough to make it run like poo.

 

Well guys, I figured out my problem. It was only the coil pack and now it runs like a champ. I will have to wait and see if it starts running crappy when it gets wet still. I really hope it doesn't.

 

Be sure to use dieletric grease inside the plug boots to keep moisture out.