I have a 93 F150 with a 302 and auto transmisson.
I think I need to replace my throttle postion sensor (TPS).
Is this hard to do, do i just replace it , or will I have to adjust anything after
I replace it.

 

Before you start aimlessly replacing parts, what are the symptoms your truck is producing? As for the difficulty of removing it and reinstalling another it is fairly simple. It is located obviously by the throttlebody, but on the underside of it. Make sure to unhook the battery for about 5 minutes after you replace the sensor, or any sensor or actuator for that matter. This will reset the computer and clear the faulty codes that the sensor might have been producing, and also removes any of the data that the computer used to try and compensate for it.

 

My truck starts ok, idles ok and when I go a couple of blocks the engine feels like it missing out.. When I stop and then go the motor almost stalls. Sometime it does not have power to go moving and the engine will lope. I put a code reader on it and I got code #41 and 63.

<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>

41 – Hego (HO2S) sensor signal out of range/always lean

63 – Throttle Position (TP) circuit fault, below minimum voltage

 

Then i would say replace the tps, and the o2 sensor since they are both not to terribly exspensive and the o2 sensor is a wear item. Also, if its throwing codes then it can't hurt to replace the part, but still check wiring and connections before you get to carried away.

 

Woah woah..

You can TEST the TPS to find out if the sensor is giving a false reading...before replacing it.

Think about it for a second..."below minimum voltage"...that means the computer is getting a voltage that is lower than spec...that could be caused by a corroded or bad wire, right? Right.

It can hurt to replace the part if it's functioning correctly and you didn't have to replace it but you spent the money on it.

Although you did say to check wiring and connections you didn't go into depth...

My advice is to first get out some paper clips and slide them into the connector at the TPS (with the key off). There is a black wire that is ground, a 5v reference wire, and a signal wire. The voltage reference wire will have a constant 5v. The signal wire voltage should be about .9v at closed throttle, about 4.5v at wide open...and have a smooth increase in voltage as the throttle is opened.

Check for voltage spikes as a TPS is a potentiometer and often times when they fail they create voltage spikes across their span of movement (same with EGR position sensor).

Only have the key on when you've got the voltmeter hooked up and are checking the voltages, if you short one of those wires with the key on you'll possibly damage the computer.

If the oxygen sensor hasn't been replaced in a long time than you can replace it, those are more of a "wear" item...but you can check the voltage on that too but it probably is infact giving a lean indication. However, oxygen sensor readings can be decieving in that...an oxygen sensor reads the oxygen content in the exhaust...if it is giving an inappropriate reading (like this, lean) it doesn't necessarily mean the sensor is foul. Your engine could be running lean due to some other problem (vacuum leak, fuel system issue, other sensor issue, etc) that is making the oxygen content in the exhaust lean...and therefore the o2 sensor is reading as it should be.

I would check the TPS first, make sure that thing is putting out the right voltages. If it's not, it could be creating that o2 sensor lean reading. The TPS is a key sensor as is the o2 sensor...so if the TPS isn't reading correctly it will definitely throw off the A/F ratios.

 

1991 F-350 351 with duel thermoactive emissions/exhaust system.
2 years sense professional rebuild. Recently the motor has been hunting and sometimes stalling at traffic lights so I gave it a tune up, rotor, cap, plugs, check timing, change thermostat and coolant, air filter, some vacuum hoses. I discovered the TPS wire insulation had shrunk back about 1 inch and they were dirty so it has been a while.

I replaced the TPS and the problem still exists. The codes about 8 of them all have the same or similar diagnosis. (Signal voltage to high or low) Including MLP, TPS, MAP, Brake on Brake off, Over drive on / off, and others I don’t have list in front of me.

At this point it appears my problem is electrical. Any ideas?

Thanks Steve

 

You either have very poor wiring and connectors or a bad PCM Computer.

 

Hi I finally got back on computer. Thanks for all posts. Using code scanner I got the following codes Key on engine off 122,126,128,173,334,634
Key on engine on 129,167,536,632
Does this help? How can I diagnose bad PCM computer? The stalling is getting worse. Wiring and connectors appear OK for old truck. Also no charging system problems or lighting problems or ignition problems. Runs great except for the hunting at all rpm /stalling at low rpm.

Steve
91 F-350, 351