I have a 92 F250 with the 460. It was running incredibly rough and leaking gas. Fuel pressure regulator fixed that. However, while I was at it, I replaced TPS and MAP sensors thinking with it having been in CA desert and sitting for a while, it would be beneficial. Now that the engine is running correctly, I'm noticing the transmssion having issues - slipping, random gear changes, hard shifting (think BANG going between gears), thunk going into reverse or drive. They are intermittent but often enough I'm concerned to drive it.

Checked the fluid today and it may be a little high but red and clean.

I read the article most often posted - Fuel Injection Technical Library » Throttle Position Sensor (TPS) about the TPS and am a tad confused. When I stick a multimeter into the back of the top TPS connector, I'm getting between 15 and 25 volts showing when I have on 50V (my meter goes from 2.5V to 50V). When I put on 2.5v it just pegs. I'm grounding to negative post on battery. Is that the correct one to be testing? Mine is flip flopped from the one in the picture but seems correct. I'm not getting any motion on the meter when I move the throttle by hand on the throttle body I've tried both old sensor and new one with the same results. Makes me think I'm doing something wrong but not sure what. Is there a way to adjust the throttle to vary the voltage if it's off? My truck idles about 1100RPMs which seems almost twice as high as it should according to Chiltons.

Seeing I don't think I had transmission issues prior to replacing the TPS and MAP sensors, I'm expecting that's the problem. I put the original one back on with the same results. Seems like I put it just a hair clockwise of where it bolts and then spin it 1/8 of a turn or so, moving the throttle with it, for the bolt holes to line up. is this correct?

Is there a sensor on the transmission I should be looking at? Anything I'm overlooking?

thanks!

 

You need to check voltage between the negative battery post and the green TPS wire.

It sounds like you're using an old analog volt meter?

 

Think all the wires are striped. I'll check tomorrow. Yes, an old analog meter.

 

Did you read the article closely enough? Because according to that article, you should be checking the TPS voltage between the TPS and SIG RTN pins while backprobing the harness with the key on, engine off. And you should be reading LESS THAN 1 volt (at least 0.6v)

Also, which type of TPS do you have?? Is it adjustable? If so, you're going to need your meter to make sure it's properly adjusted.

I'd really recommend you get a digital meter. They're really cheap for a basic function meter- around $12-$15.

Also, whenever you change any sensors, you should be resetting the computer and clearing trouble codes so the computer can learn the input values of the new sensors.

 

when you replaced the sensor, I assume you used OEM and not an aftermarket one?....sorry I skipped post where you tried old one again....disregard this post

 

By backprobing I assume it means putting the leads in the connector where the wires go in the back? Only way to get it while it's plugged in.

Going to borrow digital meter from a coworker today.

Is there a way to adjust the stock one? Since it was still having problems after going back to that, either it's now bad as well or I can't read.

When I was looking at the link, I thought the only time you went between TPS and SIG RTN was to verify the initial 5V?

 

The TPS will have the wires going to a plug about 6 inches away. This is where you stick the probes into the plug to back probe it.


When working with the TPS the old analog meter is the only one to use. The digital meter will not work well when checking the TPS going up the ohm scale.

No, the TPS in non-adjustable.

SIG RTN is the same as the NEG post of the battery, the wires just pass through the computer before getting to the NEG post.

You should read 5VDC with the key on and the TP wire should read under 1VDC with the throttle closed and under 5VDC at WOT.

 

Spent some time working on it and I didn't see another plug. Just the one that plugs into tps. There are three wires, white with green stripe, solid grey and black with white stripe. I stuck a pin through the grey one (looks like maybe grey/white according to Haynes) and was able to get a good signal. Meter started just below one and as i rotated throttle, it went up till it pegged at 2.5.

Odd thing, when I test with it unplugged to get the base voltage, I'm not getting anything?

I can take pics if it would help. I'm confused. Truck runs great but idles a little high. Almost looks like idle set screw has been messed with but I wouldn't bet on it.

What would y'all recommend as next step? Seems like the TPS that was on the truck is fine. I have unplugged the negative battery cable to give it time to reset, see if that does anything.

 

Did you have the key on when you got nothing?

Here is the wiring of the TPS:


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thanks for the schematic. Looks like engine control module or ground. I know the battery clamps look like crap. I'm going to replace the negative. Any idea where it bolts under the truck? I looked under briefly and it appears to go under the motor right above the front axle.

Also going to put the old MAP sensor back in. who knows ... can't hurt, right?

 

Ground from battery is bolted straight to the block usually, with a little lead that gets attached to body of vehicle. Not too difficult. Make sure spots you are attaching the ground wire to are rust & paint free, to ensure good contact.

 

Note that the body ground or the NEG post small wire ground and not the engine ground is the ground for the sensors and the computer.

The computer and sensors ground is one of the small wires leaving the body ground in this photo below:


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Yes - I have that connected. I'll clean it as well. I see the bigger cable going down next to motor where there's another connection prior to going under the block. Looks like if I take that tire off I can probably track it down.

Thanks for the help. Really hope I can figure it out and not actually the transmission!

 

If it cranks OK the engine ground is more than likely OK.

Someone used a RED cable for ground on this engine but it should be Black.
Just showing the location as this is the only photo I have of that ground point but it is the same as yours.


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Any CEL? Mine was doing this same thing and the solenoid pack in the trans was bad. Pull the plug on the right side of the trans on the top flat above the pan by the CAT. Use a mirror and see if there is any atf in it. If it is, its toast.