TPS & Tranny?
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Junior User
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TPS & Tranny?
I have a '95 F150 302, 4x4, auto trans. Its been sitting for a few months while I tracked down and replaced the fuel tank (leaked). When I got it going to day it wouldn't start unless I held the throttle at WOT. I proceeded to drive it to the gas station where I discovered that it would not shift. It did shift to second when I moved the selector there. I got a check engine light when I was driving it then it went out. I pulled the codes and all I got was a 121 & 123 that related to the TPS outputting a higher voltage then expected. Could the TPS cause it not to shift properly and the starting problem? Also I could not get the truck to start for the KOER test. (started as soon as I removed the test jumper) The idle is poor and none of these problem were evident when I parked it. TIA!
Post Fiend
Joined: Nov 2001
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From: Topsfield, MA
The TPS is going to affect your tranny's shifting. Get out the volt meter w/ some paper clips. Slide the paper clips into the connector where the TPS is and check the voltages it's producing. It should be around .96v at closed throttle, and I think 4.5v for WOT. But also slowly move the throttle looking for blips in the voltage (indicating a bad sensor). The TPS is a pretty important sensor for the EFI.
Do all the work w/ the key off and test the sensor voltage with the key on-engine off. Don't let the wires short or it could damage the computer.
Do all the work w/ the key off and test the sensor voltage with the key on-engine off. Don't let the wires short or it could damage the computer.
Post Fiend
Joined: Apr 2004
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From: Lafayette, IN
What Justin said. Plus, the TPS DOES affect the shifting of an electronically-controlled tranny--I'm guessing you have the AODE, right? My TPS went out on me earlier this spring, and I thought the tranny was going to dump itself all over the road. Rev up, slam into gear, not shift at the normal speeds and throttle positions, no torque converter lockup. It felt like everything on the truck was going bad, but it was just the one part, the TPS.
Jason
Jason
Post Fiend
Joined: Nov 2001
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From: Topsfield, MA
One will be ground, one will be a reference wire, and the other the signal voltage wire. Find the ground, then probe the other two wires. One will have a constant probably 5 volts, the other will vary and should be .96-4.5v depending on throttle position.
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Post Fiend
Joined: Apr 2004
Posts: 6,473
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From: Lafayette, IN
I don't recall what I paid for the one on my 351 this year, but it looks essentially the same as the one on the 302, probably the same part. I think it was $40-50 or so.
Jason
Jason
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Junior User
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FYI I replaced the TPS and cleaned out the throttle body (wow, is all I can say). Problem solved. No codes, trans shifts great, starts good again and the idle is solid. Thanks for the help guys.
I paid $33 for the TPS and $2 for the throttle body to upper-intake gasket.
I paid $33 for the TPS and $2 for the throttle body to upper-intake gasket.