I've got a 1997 F150 with a 4.2L. Just turned over 95K and has run excellent for the last 50K miles. It quit on me going home from work yesterday. I got about 1 mile down the road and it felt like I took my foot off the throttle. The engine continued to run, but apparently at just an idle. I pulled off the road and when I put my foot on the clutch, the engine shuttered and then cut off. I tried cranking several times, but no luck. I then tried different things, one of which was to pump the gas pedal and then hold it about 3/4 to the floor while cranking. It started, and would run if I kept it revved up. I made it home and it cut off again.....whew!! This morning I drove to work and it cut off at a stop sign, and once again when I pulled into the parking lot. Fortunately for me I work in a garage (as partman) and we hooked a Snap On scan tool to it. Two codes were pulled....P0102 and P1121. (1) MAF/UAF CKT low input and (2)TP sensor inconsistant with MAF. I wrote them in a hurry, the codes are right but the description may be off a little. Looks like a toss up between the TP sensor and the MAF sensor. Which sensor (if either) would you folks recommend I start with, or is there something else I should try ?? Any help would be appreciated.

Thanks

Guy

 

Only runs when revved? I am thinking TPS. If the TPS is bad and it thinks X CFM is flowing through the throttle body but the MAF thinks Y is flowing through then you get a code and conflict. A faulty MAF would still allow the truck to run just not as well where a TPS would cause stalling like you have described since it thinkes the throttle is open/closed more than it reallyis. Check your TPS and go from there.

 

Let me make it a little more clear. After it stalls/cuts off, it will only start and run when revved. After it gets going, it will run and idle normally.....until it decides to cut off again. Thanks for your input.....

 

What's the best way to check the TPS ?? Also, I cleared the codes, ran the truck until the check engine light came on and put it on the scan tool again. This time only the P0102 code came up with a KOEO scan. With a KOER scan, a P1101 code came up. I'm trying hard not to have to go to the dealer on this and if I buy a sensor, I want to get it right the first time. Thanks again.

Guy

 

The 1121 is because of having to start it with the throttle open. I would find a friend with the same model truck and swap out the maf before buying one. I personally have not seen the tp go bad on these motors yet. Most likely the maf. It is inside the black plastic piece that you take off to service the air filter. Just a thought because most electrical parts cannot be returned after purchase. Make sure that is what it is prior to buying anything.

Robbie

 

You can force the computer to ignore certain sensors by disconnecting them. This works for the MAF and the TPS among others. You will get a CEL, but if the drivability concern is corrected with a sensor disconnected, there is a problem related to that sensor. Only one sensor at a time should be disconnected. Works particularly well for diagnosing MAF-related issues.

Steve

 

Hope you get it fixed bud!

 

Thanks to all for your input. Installed a new MAF today and WOW, the engine runs great !! Even got rid of that little miss it had when I lugged it. Thanks again.

Guy