so I'm replacing my throttle position sensor...

(88 f150 - 302 auto)

On mine it's bottom mounted so I have to remove the throttle body.

The throttle "plenum" area (sorry I'm not sure I'm up on the terminology) the big area behind the throttle valves that directs the air to the cylinders - is THICK with black gunk/grease.

Kind of nervous about that -but ignoring it for the moment - unless somebody has something to say about it.

But my immediate question is - between the throttle body/butterfuly valves and that plenum "box" is some kind of spacer block -about an inch thick. I'm assuming it's some kind of aftermarket "triple your gas mileage" type of device because it has twisted "vortex" kind of shapes in the two large air flow holes.

So a few questions.

DOES it do anything? Is it worth keeping in there? I'm leaning heavily towards tossing it.

AND - if I remove it - is there something else that's supposed to go there? In other words, when the previous owner installed this spacer, would it have been in place of a smaller stock one???

Or should I be able to just toss it and put the throttle body/valves back on directly?

 

Yeah that's one of those vortex TB spacers, toss it and put the TB back on with shorter bolts.. you won't notice any difference.
And no there is no stock TB spacer because swirling the air 2 feet upsteam of where the fuel in injected has NO effect whatsoever on anything.

 

Yep, junk it. It's been proven worthless time and time again.

I would clean the junk out of the throttle body as best you can. You can use any kind of solvent you want. Brake cleaner, carb cleaner, TB cleaner, etc.

Also make sure you adjust the TPS after you install it. A Haynes or Chiltons manual has the procedure.

 

You just asked my next question for me -

As I was putting the new sensor on - I was thinking that it would seem you'd want that thing positioned just right - a few degrees off could cause issues.

- but - looking throught he chilton manual - there's no mention of how to adjust it.

There is a chart of volts per degree of throttle shaft rotation...

... but - volts? Between what and what? it doesn't say.

I'm assuming between one of the three wires and ground - but any idea which one?

Guess I can play around to figure it out -

 

You need to couple needles to probe 2 wires with the TPS mounted on the TB and connected to the electrical harness, then turn the ignition to run and measure the closed throttle voltage which should be somewhere between 0.5 to 0.99v but not more, and WOT voltage which should be 4.5 to 5v but not more. If it falls anywhere in this range you're good since the computer takes a reading of the closed TPS voltage at startup and uses that as the baseline for the next drive cycle. Note you can do this before re-mounting the TB on the engine, if the TPS needs any adjustment it's typically done by elongating the mouning holes, if that doesn't allow enough movement to bring the numbers within spec the sensor is either mounded wrong or is faulty.
DO NOT under any circumstances adjust the throttle plate stop screw on the throttlebody.

 

thank you Paul.

I will need to check those levels.

I took the "can't be any worse than it was" approach and put it all together and ran it without measuring.

The good news is that the throttle response is WAAAY better. My problem is fixed.

But the bad news is the idle speed is too high. So I'll end up taking it all apart again to adjust it.

That's what I get for rushing.

 

If the idle speed is too high after R/Ring the throttle body then you most likely have a vacuum leak. There is no "adjustment" for the idle RPM. The PCM takes care of that.

If the TPS output value is not in the range Paul stated then you have a bad TPS, take it back. The TPS used on most of the trucks in the vintage is non-adjustable for a reason.

 

actually the one thing the chilton manual does say about the tps is to put the TPS on, and rotate it clockwise into position, and that failure to follow that step may result in high idle speeds.

I did of course follow those directions - but perhaps I missed something.

The throttle body isn't so bad to remove - I'll just try again - and measure the voltage while I'm at it.