My check engine light never came on. I was quite honestly fed up with my truck and resigned to the fact that the motor would never have any power. Then I stopped trying to be cheap and bought a code reader. Best money ever spent. The key on/engine off told me the map sensor was bad so I replaced it. The key on/engine running test told me my O2 sensor was bad. I haven't changed that yet.
And I to love my 1992 Ford F250 5.8L that's rated at OVER 8600 lbs. I too have been having this problem which I believe I have narrowed down to the TPS. My question is: Will I have to reset the TPS if I remove it and replace it with a new one. Also, can this problem be caused by a bad MAP Sensor? I am at wits end! I have probably put several thousand dollars into the engine because of a nasty short in the electrical system that knocked out all my fusible links, my alternator, my starter and so on so forth. However, the EEC-IV and other electronics were not affected. This puzzles me!!?? I would appreciate your reply very much. Thanks.
Sometimes a Mass Air Flow sensor will cause same symptoms. I had a issue like this with my 94' Ranger and I asked my mechanic friend about it. He told me to disconnect it and if that was my problem my engine would run better.
It would from time to time act like it was running out of gas, lacked power engine light would come on. I would take it out of gear and rev it a couple times engine light would go out and I was good for a while.
After unplugging it it ran great, so that was my problem then. I asked how much they were he said lets look at it 1st, we took it out and there was a small speck of dust on it, we blew it off with electronics air in a can. I was all set no money spent on new sensor. So check that if you are lacking power and your engine light comes on with lack of power.
The original post is almost twelve years old, and the post before yours is was posted over four years ago. Hopefully they got the issue resolved by now lol.
BTW, welcome to the forum, lots of knowledgeable folks on here. Hopefully you'll stick around and add to the knowledge base.
Be careful using an auto-ranging DVM, the display has some lag and it may change ranges on you during the testing. I manually set the voltage range then slowly open throttle while watching the meter (Key On Engine Off). It may take a few tries to determine if there are any dips or spikes in the output signal. It should sweep linearly from closed to open throttle.
I had a bad tps in my 95 351w. Bought the truck in April 2015 and noticed it didn't have much power and was kind of disappointed in my purchase. As the weather started to get hotter the truck ran worse. During days of say 80 degrees or hotter the truck would barely accelerate, probably took a good 3 or 4 minutes to get to 60 mph with the pedal to the floor. Had my mechanic look at it. He read the codes and came up with tps low circuit I believe. He replaced it and it felt like a brand new motor.
Just to throw my .02 into this very old thread...my 2003 jeep was downshifting constantly if I didn't hold the gas pedal completely still when I was cruising. The slightest bump in the road would make my foot move and the jeep would downshift. Turned out to be the TPS.
Both examples above are why you properly diagnose the issue. Start with the code check, if that passes break out the meter. For the sake of your wallet thickness please do not start throwing parts at the issue. The cheaper aftermarket TPS sensors are well known to be inferior to a Motorcraft brand. It's too much money to throw away for no reason.
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