I have read all threads relating to this problem but still no resolution. Here's the scoop:

I have a 2000 f150xl with the 4.2, 67k miles and well taken care of.

About a month ago the truck started idling rough and I pulled codes, P0301, P0302, P0304, P0305. I reset codes and restarted and the truck ran fine for about a month, then I started getting rough idle and hesitation when leaving redlights, no codes have ever surfaced since. I changed wires, plugs and coil pack, still have same problem. I removed EGR and checked for plugged ports, all looks very clean. I have no codes and the truck idles rough, hesitates, and backfires on accelleration. I am at a loss on what to do next.

I do suspect that I got bad gas at Chevron station in my truck and car prior to this. Both then started running poorly. Car is fine now but truck is still bad. I did put 2 cans of STP treatment and 22 gal. of Mobile Super unleaded.

Questions: Do I need to drive a while for the PCM to level out the engine?
Do I need to burn up a full tank of gas (with STP) and see if it resolves itself?
Am I chasing my tail with the suspected "dirty fuel" theory?
Can there be a bad MAF, DPFE, IAC sensor that went bad and the PCM is not reporting the code?


FYI, I used new motorcraft plugs and wires.

 

I'm unsure if they are related (but it is likely) I had the hesitation and rough idle problem for quite some time (no backfire though that I can remember) and fixed it by replacing three cracked vacuum lines throughout the system and cleaning the egr.

Hope that helps you.

 

The only way to clear up a dirty fuel problem is drop the tank and flush it.

 

Guys,

Thanks for the insight. I gave it a rest for a day and thought thru it again. This is what I found....

About a month ago the truck was on empty and been having good luck with Chevron Techron gas. So I filled it up (23 gal) at a different Chevron station than the normal one I get gas at. I noticed that the pumps were off by about 2 gal. I am very keen to tracking milage and know my tank size (25gal) and suspected some meter cheating was going on. (I am sure his meters were rigged, especially with premium at 3.39/gal). Not only was the meters incorrect, there was/is water in his ground tanks. I realized this because I also filled up my other car there about a week after and it also had a slightly rough idle (which it never did).

So by thinking thru all events and putting it all together was easy. So after adding 2 bottles of isopropol alcohol and driving 2-3 miles all the hesitation and backfiring magically stopped.

My advice, BEWARE of privately owned stations, especially ones with the older style pumps and tanks. Thank goodness this only cost me about 7 hours in troubleshooting time and $120 for new plugs and wires. Now the 4.2runs like the day I bought it.