My truck may run normal for 15 minutes and then run rough (loping almost stalling out) or it may run rough from the first time I start it that day. I know it isn't an issue with the catalytic converter,that has been dealt with before. I pulled the negative cable to clear codes then ran it and checked codes again.
KOEO 159,159,111,111
KOER 412,159,129,167
This all leads me to believe it is a MAF sensor issue,I took it apart and cleaned the sensor (it appeared in good shape nothing broken and no dead bugs stuck on it) still have the same problem. I checked for voltage at the harness there was no issue.
While the truck is running,chugging etc, I unplug the MAF wiring harness and it begins to idle normally. It even drives normally for a few minutes then the throttle developes a mind of it's own regardless of what I do with the accelerator pedal.
My intention is to replace the MAF but I thought I might post this to see if any one with more knowledge may have any advice before I go to that expense.
It is a 4.0 6 cyl 2wd with 358,569 miles on it.
Thanks in advance for any advice.

 

Ok. I went ahead and changed the MAF and the truck does run better,however, it still isn't right. I also have had issues with filling the gas tank and read about clogged vent tubes etc. Problem is I cannot locate where the vent tube is back by the tank. I understand that it runs to the front to the evac canister but I am unsure about where it starts.
Out of desperation I am going to try blowing compressed air through the tube from the engine compartment back. I figure I will be changing a fuel filter in a bit if this actually works. I just hope there is no check valve or similar item that I will damage.
If anybody reads this and has advice I would appreciate it a great deal.

 

There is a line at the carbon canister that comes directly from the top of the fuel tank. There is also a vent on top of the canister that should allow pressure when filling to escape. There is a good possibility the carbon has deteriorated to the point it will not allow air to escape. You may wind up replacing the canister itself. Let us know what you find, thanks.

 

Pulled the canister and was able to put gas in truck normally but it had no effect on how the truck ran. I went ahead and cleaned it with some carb cleaner and compressed air. I am now thinking it may be the TPS, I put the meter on it (KOEO) at idle it showed .2v at full throttle it showed 13v, both are outside of range so I am going to risk the $40 to replace it.
After buying the new MAF and the bother of troubleshooting many different items because of codes I can not stress enough how important it is to read more than just the bit that explains how to change a part. Hopefully I will not forget this lesson.
Just to be safe I stopped by the bank and applied for a vehicle loan,I am supposed to hear from them tomorrow morning as well as pick up my TPS in the a.m. ,so one way or another by tomorrow evening my problems with this truck will be solved. After 358000 miles and less than 3 grand in repairs over 19 years I think I will by another Ford if I do end up buying.

 

Replaced the TPS,no change. MAF unplugged runs fairly decent, MAF plugged in won't idle and bucks like crazy while driving. Drove it 25 miles at 55mph to see if the PCM would relearn a fuel strategy, absolutely no change. Going to double check plugs and wires, unless it is something as simple as that I will just use it as target practice. Should also mention MAF unplugged check engine light on runs ok,MAF plugged in no CEL but doesn't want to run.

 

Usually if the engine runs fine with the MAF unplugged, the Maf is defective ! Even new ones come through defective !! Just because it is "new" is no guarantee these days , especially with imported junk.