Does anybody know what the ohms reading is supposed to be on a 90' 2.6 TPS. There is 3 pins, between two of them I get a dead short around half throttle.Between one of those pins and the third pin it is a dead short all the way. My repair manual doesnt say what it should be.

Simple question, but you need to think of how the TPS works. The TPS is a basic position sensor, with a mechanically-linked wiper arm that sweeps across a resistor (generally just a grounded coil of wire, driven by a reference signal). As the wiper arm moves on the resistor, it's signal voltage output changes. The closer the wiper arm gets to the signal input end of the coil, the higher the signal output; the closer the wiper arm gets to the grounded end of the coil, the lower the signal output.
* At idle, the resistance between the signal reference and signal output is high.
* At WFO, the resistance between the signal reference and signal output is low.

So basically, two wires should have high continuity with the linkage rotated all the way one way, and two wires should have high continuity with the linkage rotated all the way the other way. The one wire shared in this instance is the signal voltage output, and the other two wires are ground and signal voltage. Back-trace the engine harness with the key off to identify which is which.

Randii

Just one quick question!!! I wasnt getting any low to high or vice versa, except perfect ohms at half throttle. Wouldnt that mean that the coil inside is broke around half way? The reason why I am even checking it is because I am having some issues w/ my truck not running well, and when it does run the throttle seems to die around 1/3 throttle or so.Would a bad throttle sensor make it hard to crank and run also.

Joe-

I'll emphasize it again. Get a manual or get a better one. You are chasing gremilns and without a manual to guide you, you are moving forward blindly. Haynes does not talk about it, but Chiltons does. A Helm would be best, as it includes much more specific info along with some adjustment procedures beyond basic testing.

LINK

It really is a WOT switch. Randii gave a great discription of a TPS, that does give a voltage reading, modified by resistance, that is related to throttle position. On the 2.6, you get three states. Idle, off idle, and WOT.

The link above tells you what to do.

Good Luck,
Michael

Only on the automatics... the manual trans rigs have just a switch. What've you got Joe ?

If it's the switch type, one of the pins is common (I'd have to look to see which is which) --- one contact will be closed (shorted) when the throttle is at idle, the other will be shorted from about 3/4 throttle to full.

Dinner's ready...

Sorry, guys, I guess I've got EEC-IV on my mind! <img src="/forums/images/graemlins/zombie.gif" alt="" />

Randii

No worse than me tellin' the guy he couldn't adjust the valves with the head off... jeeze, shades of my SBC days I guess!

I wrote this to Joe in a PM, and thought it might be good to put here also:

On the TPS: It's not "like" a switch, it _IS_ a switch.

To be exact, it's a SINGLE POLE, DOUBLE THROW rotary switch.

Inside it, there's a CAM, a CENTER CONTACT that gets pushed by bumps in the cam either UP or DOWN, and two other contacts, one for IDLE, and one for WOT.

There's THREE conditions of this switch.

1. ON IDLE

This is when the throttle is fully closed. The center contact of the switch will be shorted to the top contact of the switch. There should be OPEN from the center contact to the bottom contact.

2. CRUISING

Throttle between about 1 degree open, and appx 3/4 open. There should be NO CONTACT between ANY of the 3 pins.

3. WOT

Throttle between 3/4 and full. There should be contact (SHORTED) between the bottom contact, and the center contact. It should be OPEN from the center contact to the top contact.

There should never be any contact between the top and the bottom, at any throttle position.

If you've got anything different than that, you will have one very confused computer...

HTH someone.