I'm a tad old school when it comes to a couple things automotive...(1) I know nothing of OBC and sensors and so on, I have always had older Fords...(2) I Never take my vehicle to a mechanic if there is a possibility I can do it and learn something.
With that being said, I have a 2001 F150 2x4 SuperCrew with a 4.6L. For about a year i have been experiencing the same symptoms. The truck runs great til it warmed up then would hesitate or buck during acceleration. When it first started, the Check engine light came on and i took it to a trusted Mechanic I know. They hooked it up and said it was a misfire on Cyl 5. I bought a new Coil pack, installed it and problem solved! about 4 months later same thing started hapening. I figured I had done all me regular maint with the exception of a tune up. However I wasnt paying $400+ for a tuneup. I bought new plugs and replaced them...yeah that was a treat, but once again...problem solved.
About a month ago I felt it beginning again. I bought an OBD2 code reader and figured I would wait til the light came on, find the code and change which ever coil pack was toast this time.
Go figure it didnt say misfire this time....instead it said P1132 (.Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Rich - Bank No. 1)...and the EV was flashing for EVAP sensor.
OK...where do I start?
From what I can gather up on this forum, I should start with cleaning the MAF and IAC...check my fuses, also find the Charcoal canister clean it, fix or replace it if necessary, check the lines?
Is there anyway to pin point this down to less than this? It seems like a pretty broad fix.
The only other thing that is wrong to my knowlege on this truck is the dipstick oil tube. It has brocken off at the motor where it is connected, but is still seated in the hole just not connected on the tube to the motor. Nothing leaks from it I keep a close eye on it and I do have it wired in place for the time being til the weather gets warmer to replace it. Reason I mentioned that was that I read somewhere that oil leaks could cause that? Makes no sense but at this point...
I dont really notice any hesitation right now because the weather has been below 0c...but I anticipate it due to weather warming into the +'s this week.
Any help would greatly be appreciated.

 

Hello ole screwel,
Just kidding.
Guess what? That broken dip stick tube likely is the cause of the 1131 code.
Reason is the crankcase is part of what is monitored for air leaks because the whole system is supposed to be closed.
Take care of that then see what's left for a problem and we will help with what's left..
A new tube should be about $15 +/- from a dealer parts dept.
Hint; you may have a hard time getting the stub out that is left in the block and the tube may seem too long to get in place.
Just cut about 1" off the bottom just enough to get it in place.
The tube uses an O ring seal in the block.
Good luck.

 

OK so now what?
I swapped out the broken Dipstick tube for a brand new one...nice of them to have them pre bent to the exact angle that makes it twice as hard to install. Is nothing easy to replace/repair on these trucks?
Anyway, I also cleaned the MAF. after doing so, I rechecked the computer and its still reading the P1132 code with the EV light flashing. Never really noticed it before but I have caught a quick scent of rich fuel a couple times. Any ideas?

 

If you did not clear the code it would take some time to clear it'self as it's not an instant repair to the PCM because the fault is still stored in memory..
Do a clear first to see what comes back because you may have more than one problem causing the confusion.
Work one issue at a time until you get them all.
Good luck.

 

Thanks, I'll Give it a shot tonight after work