throttle position sensor ?
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Joined: Sep 2005
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throttle position sensor ?
i need some help!!!! i have a ford truck f250 351w 1990. my idle seems very rich and i notice that while driving my transmission will shift to soon. i read that someone had shifting problems and changed their tp sensor and it was good as new. while t/s i checked my tp sensor and noticed at idle i was getting 4.0 volts (back probing the connector grd wire & sig wire. it appears that something is backwards. with the throttle body disconnected and with the new tp sensor connected i tried to adjust the idle position to get my 1.0 volts. i am getting 4.0volts at idle and when the throttle plate goes to full throttle the volts go down. would it be possiable that someone removed the connector pins at the tp sensor and swithed them.. there is only three wires. my connector when plugged in is, orange to brown/white, black to gray/red, orange to brown/white. i do not have any t/s codes. thanks, craig
Hotshot
Joined: Jul 2002
Posts: 14,285
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From: Bend,OR
scan for codes. there could be more compounding the issue here. you dont need to adjust the idle screw . its a pre set thing for the ecu so moving it probably didnt help. I would take back that new tps and buy one from ford. for some reason the cheap brands on some of these electric sensors just done work to well.
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i have no codes, my old tp sensor was reading the same as the new one i just bought. the manual states that there is a adjustment for the tp sensor. the sensor rotates about an 1/8 inch. this is where i'm supposed to adjust 1 volt at idle. i have about 4 volts. could anyone look at thier 351w fuel inj. eng area and see what color wires you have at the tp sensor (3 wires)( i would like to know what goes in and out of the connector). i can get the 1 volt reading if i rotate the new sensor out of its travel area without it being installed on the throttle body assy.
Lead Driver
Joined: Nov 2002
Posts: 9,557
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From: Concord, NC
Of the three wires, one is a sensor ground (black), one is a 5V reference voltage (orange), and the third is the signal wire (green), which varies voltage depending on throttle position.
Since the colors don't match like they should, I would test continuity on the wires to see what each one does. The 5V signal also goes to the EGR valve position sensor, so test continuity between (and check for 5V at the EVP with the key on) the EVP sensor and the TPS and the orange wire on the MAP sensor. All should have the 5V with the key on. The sensor ground also goes to the EVP sensor, as well as the coolant temp sensor, air temp sensor, and MAP sensor, so test continuity between all those points. Also test continuity to negative battery terminal. If those match, the only possibility for the third wire is the signal. You can test continuity between the TPS and the computer, which might be a good idea if you are unsure of the condition of the wiring.
Since the colors don't match like they should, I would test continuity on the wires to see what each one does. The 5V signal also goes to the EGR valve position sensor, so test continuity between (and check for 5V at the EVP with the key on) the EVP sensor and the TPS and the orange wire on the MAP sensor. All should have the 5V with the key on. The sensor ground also goes to the EVP sensor, as well as the coolant temp sensor, air temp sensor, and MAP sensor, so test continuity between all those points. Also test continuity to negative battery terminal. If those match, the only possibility for the third wire is the signal. You can test continuity between the TPS and the computer, which might be a good idea if you are unsure of the condition of the wiring.
