Stalling, varying idle, choppy acceleration? (5.0 XLT 2WD)

[U235]

Alright guys, buckle in, this is gonna be a hell of a "help me" thread.

My Explorer has been faithful to my family and I ever since my folks bought it brand new back in 1998. Then, about a year or two ago(my memory fails me on how long exactly), my sister rear ended somebody with it. It was in pretty rough shape, and sat for a while, but now my dad and I are slowly massaging it back into it's former glory.

So we got it running, and everything was great. But since then, a few issues have arisen.

- Very strange variation in the idle speed. I'll attach a link to a video I took of this. Note: I did not touch the gas pedal AT ALL during the recording of this video. All changes in RPM are happening without any input on my part. Also, it is pretty tame in the video, usually the idle moves up and down much quicker than what it does in the video. http://youtu.be/zQsVDeG95mU

- If I floor it from a stop, the motor will begin to rev out, then drop revs -- as if the truck had been turned off -- and then either proceed to rev up and commence ass hauling, or the motor will die completely. Usually, when this happens, the truck will not start again, unless I pop the hood, and disconnect the battery momentarily, which obviously leads me to believe that it's an electrical issue.

- Lastly, and this seems to have just recently started, is that under any ammount of acceleration, the truck feels... Choppy, if I had to think of a word to explain it. I really can't think of a way to say it without you all being able to feel it while driving, but there are little jumps, or tics, that the truck does every second or so, while under acceleration. I haven't really noticed it while cruising, though.


I've learned a hell of a lot from you folks so far, and hopefully y'all will be able to figure this one out as well. Thanks for taking the time to look!

 

[koda2000]

i have a few thoughts... do i understand you correctly in that the truck has been sitting for years?

if the truck has just been sitting for a long time it could be fuel related. today's ethanol blend fuels go bad pretty quickly. they absorb moister from the atmosphere and if the percentage of water gets too high it can separate from the gasoline. if this happens the water (being heavier than gasoline) sinks to the bottom of the tank (which is where the fuel pick-up is). you can try putting a product like Heet in the tank to put the water back in suspension. i think auto parts stores also now sell a product which is supposed to revive stale gasoline.

another thing i've seen happen (quite often) is that mice build nests in the air filter box. remove the air filter element and check.

your idle air control valve (IAC) controls your idle based on a signal from the PCM. if your IAC is dirty and/or sticking it will cause an erratic idle. remove it (two 8mm bolts) and clean it with carb or parts cleaner and an old tooth brush. the IAC gasket is usually reusable as long as you don't damage it.

if your A/C is on, you'll see a slight increase in your idle when the compressor kicks in and a slight decrease when the compressor cycles off.

 

[shadowless127]

i have a few thoughts... do i understand you correctly in that the truck has been sitting for years?

if the truck has just been sitting for a long time it could be fuel related. today's ethanol blend fuels go bad pretty quickly. they absorb moister from the atmosphere and if the percentage of water gets too high it can separate from the gasoline. if this happens the water (being heavier than gasoline) sinks to the bottom of the tank (which is where the fuel pick-up is). you can try putting a product like Heet in the tank to put the water back in suspension. i think auto parts stores also now sell a product which is supposed to revive stale gasoline.

another thing i've seen happen (quite often) is that mice build nests in the air filter box. remove the air filter element and check.

your idle air control valve (IAC) controls your idle based on a signal from the PCM. if your IAC is dirty and/or sticking it will cause an erratic idle. remove it (two 8mm bolts) and clean it with carb or parts cleaner and an old tooth brush. the IAC gasket is usually reusable as long as you don't damage it.

if your A/C is on, you'll see a slight increase in your idle when the compressor kicks in and a slight decrease when the compressor cycles off.

Everything in this post is spot on.

Would also consider changing your fuel filter and checking your plugs and wires.

Also, I forget the name of that stuff that revives stale gas, but me and my buddy used it in his boat that had a half a tank of gas when it was winterized and it helped a bit but was still not great so we topped off the tank with some fresh fuel and you never would have known.