I have a 2002 F150 with a 4.6, 2WD.

I went to start up my truck the other day, and when I did it was stuttering real bad while idling. So I ran the OBD II code, and two came up. One is a bad DPFE sensor (knew that already), and the other was a P1211 TPS not matching MAF

So as I assumed was wrong, I went and got a TPS from Autozone (motorcraft) and immediatley replaced it. Cleared the code, started the truck up. Boom P1211 code again and same symptoms.

Main symptoms include, Loss of power, Smells like it is burning rich, and horribly rough idle (Lope and sounds like its gonna die at random times)

I was curious if you think it would be the MAF sensor?

 

The trap you fell into is trying to depend on the code only to tell you what part to replace.
The accurate code suggestion is the voltage to the sensor is in fault.
What you need to do is use a volt meter to measure what you have coming from the PCM and what comes off the center terminal of the sensor.
Then you know if the signal voltage supply is ok or the TPS is faulty.
You can check the TPS with the ohm meter function to see if it has any rough or open spots in it's rotation.
What you need to know about testing voltages is not to reference the negitive to the motor ground because the voltage supply is 'floating' or isolated from chassis ground and must be checked/ referenced to the return lead of the supply pair.
It is true that with no feed back from the TPS, the PCM sees it as a mismatch with the expected mass air meter output, so messes up the fueling.
Make the checks and see what you have.
There may be a harness rub through or break at some point.
Also this supply feeds other funtions that may well add to the total issue you experience causing more confusion.
Good luck.

 

O wow quick reply.

I will have to get ahold of a volt meter (my other ones lent out at the time)

Any idea what the voltages should look like going to the TPS?

And where would be the most immediate place to check for the harness breaks/rub throughs?

 

When was the last time you cleaned the MAF and TB?

 

Cleaned my MAF last night.

Cleaned my TB about a month ago.


What are the common symptoms of a blown MAF?

 

Mine acted similar to that until I cleaned the MAF and TB. Then got a tune up. Also had some vaccuum leaks fixed. So I was just wondering.

 

The output from the PCM internal supply should be about 5 volts +/- a tenth or two.
The output from the sensor at idle will be anywhere from .5 to about 1.2 volts and move higher as you operate the throttle.
Some will tell you that the TPS should be adjusted to a value of about .98 volt +/- but it does not make any difference because the PCM does an "auto zero" as a reference everytime the ignition is turned on to the RUN position.
For those who are interested in this, the reason this auto zero feature is done is to eliminate the TPS resistance changes from heat, wear and small changes in the PCM supply voltage affecting the throttle angle signal that has to track the mass air meter output for accurate fuel and timing changes vs load and rpm..

 

After checking all the wires for the TPS.

I decided to unplug the MAF And hey guess what?

Ran near perfect.

Called O'Reily's ordered a new one, backed with a lifetime warranty!


Just gotta wait for my paycheck.

 

Good enough.
What I did not tell you in my last reply #7 is the 5 volt supply is used by a number of sensors such that another one on the line can short out the supply and cause other additional problems that cause confusion.
I did mention it in reply #2, last sentence.
Good luck.