Throttle Position Sensor Issue
 

I bought a 1994 with 16,700 miles. The transmission was replaced at 16,620 due to setting so long undriven (Ford dealer did it). The shifting is eratic when the cruise is set (in and out of overdrive). I spoke to the transmission rebuilder and they said it was the TPS. I had it checked and my Ford dealer says it's okay. Went back to them and again TPS, suggested I have someone else check it. Any ideas?

you need to check for codes. no codes no problem. TPS will register 121-125 i believe. As for the shifts, your only supposed to use OD will on the highway, when in town you should turn it off. The E4OD will allways shift too early on you, and you'll have to step on it to get it to downshift, it's just not a very town friendly tranny.

you can check the TPS yourself if you really want, its not hard. I recently had to replace mine because the idle voltage was too high and caused my truck to idle around 1700rpm.

You can probe the black and green wires, and with the throttle at idle you should read between .5 and 1V. I was getting 1.5. if you adjust the throttle to fully open position you should get between 4 and 5V. (The way i did this was using 2 small needles and poked through the wire insulation, then put some rtv on the holes to seal it back.

You can also disconnect it and check resistance. Throttle closed should read 4-5kOhms and fully open about 350 Ohms. This should also be a smooth transistion both in the adjustment and readings.

This is all according to the Haynes manual. As well, "any problems in the TPS or circuit will set a code 23,55 or 63 or 122-125 for the three digit system." I had a 121.

yep i just changed mine out yesterday, couldn't believe how dirty the TB was. The ideal voltage at idle is 1v.

It has thrown no codes. I checked the voltage last night and it was 1V at idle. I still think the problem is transmission related. Last night on the way home, I had to just shut off the cruise. It's agravating!

your vss sensor in the rear diff will also cause this. remove it and clean it. if it continues remove the rear cover and inspect the tone ring for wear or missing teeth. also your MLP solenoid on the tranny could be messed up some tranny shops over look that as well. also hows the fluid level in your tranny while the motor is running?

Thanks for the tips! I'll get greasy again tonight I guess....LOL

I had the same issue on 90 F150 I6 E4OD. I replaced the MPLS first per a TSB and that did not fix it. It was the TPS after all even though it tested fine. Took me two weeks before I found the problem. Ran fine until I sold it a year or so later.

Okay the problem has been solved. We were all wrong. It was a collapsed catalitic converter. The converter had actuallly collapsed inside. My buddy, a Ford Tech, came over last night and drove it. The very first thing he said was exhaust back pressure! I had doubts but we checked the flow and you guessed it. He said he has found this in more than one vehicle that has sat for an extended period. So, today I am having true duals put on with two high flow cats. Might as well go all out huh?

why are you wanting duals. they dont perform as well as a custom single exhaust setup. were do you plan on putting your o2 sensor? duals are meant for hi rpm hi hp motors. not stock low rpm uses. if its for looks just get the dual after the muffler itself. that would aleast be better

My 1989 F-150 w/ 5.0L ran so much better after I put the duals on it. I also picked up about 2 mpg. The same guy that did it and is doing this one. I believe he put the O2 sensor in the X-pipe between the cats and the muffler. He used a 2-in / 2-out single three chamber flowmaster on my old one. Both pipes exited the rear of the pass. side rear wheel just like a stock 5.8L. He used 3" s/s rolled tips that were tilted just enough to allow them to drain. The sound was amazing. Quiet until you stood in it.

your truck probably ran better after you put duals on it because there were problems with the system you took off, it was stock, or it was too restrictive.

That could be but for whatever the reason, I was happy camper!

yeah its your truck and you can do whatever you want to it and if it makes you happy then thats good. I know your gonna feel a good power boost getting rid of that bad cat and some more for any improvements in the exhaust. Good luck with it though.

the o2 sensor should really be installed before the cat not after otherwise it will give false readings to the ecu. but like tiger said its your rig. good luck