TPS adjustment

[garyweb3]

According to the TBI manual the voltage reading at terminals B and C should be 5v at WOT. It doesn't say what it should read with the throttle closed but I assume less than 5v. My TPS doesn't vary at all always reads 5v no matter the position of the throttle. This is a new TPS because the previous one read the same as this one, no difference always 5v and I was advised it was bad. This doesn't sound right because how does the ECM know how far the throttle is open. Also checked between terminals A and B and read 4.85v at WOT. That does vary when the throttle is opened even if it's higher than the manual specifies max of 4.6-4.7v. What could be wrong?

[fiatslug87]

Make sure the lever on the TPS is under the post on the TB.

 

And follow Cruiser’s TPS tip.

 

[garyweb3]

I have the TPS removed and testing it like that. Manually moving the lever.

[fiatslug87]

What engine/year do you have? Put your truck’s info in your signature.

[garyweb3]

1 minute ago, fiatslug87 said:

What engine/year do you have? Put your truck’s info in your signature.

1987 Comanche w/2.5L.

[eaglescout526]

I think your reading the voltage supply to the sensor. Good it’s getting 5v but the voltage from A and B is what you’re after. WOT between the two should be between 4.62v and 4.65v. 

[Eagle_SX4]

The TPS will move farther than the throttle (both opened and closed) which is why adjusting it is critical.

 

The max voltage with the TPS off the throttle body will be higher than when it is installed adjusted properly and the throttle maxed out.

[garyweb3]

Ok but why doesn't it vary at all? It's 5v at closed throttle and open throttle no change from one or the other. How will the ECM know what position the throttle is?

[eaglescout526]

46 minutes ago, garyweb3 said:

Ok but why doesn't it vary at all? It's 5v at closed throttle and open throttle no change from one or the other. How will the ECM know what position the throttle is?

That’s because that’s supply voltage to the sensor. If your probing B and C you should see 5v constant regardless of the position. A and B is the input voltage to the ECU so it does know what it’s position is. 

[garyweb3]

Since that does vary the TPS should be good?

[eaglescout526]

15 minutes ago, garyweb3 said:

Since that does vary the TPS should be good?

Yes. If it sweeps clearly with no hiccups, it’s good. 

[garyweb3]

Thanks for the information. It's much clearer and makes more sense than the TBI manual.

[eaglescout526]

23 minutes ago, garyweb3 said:

Thanks for the information. It's much clearer and makes more sense than the TBI manual.

Really? I thought the TBI manual made sense…to me at least. 

[garyweb3]

It does but it didn't explain the voltages that I should get like you did. It doesn't specify that 5v will be seen at the full range of movement of the throttle. I thought that measurement was what the ECM see's to varify the throttle position.

[llhat]

go back and review what was posted above.   there's a lot of explanation there.... 

here's another link so you don't have to scroll.

 

 

 

[eaglescout526]

2 hours ago, garyweb3 said:

It does but it didn't explain the voltages that I should get like you did. It doesn't specify that 5v will be seen at the full range of movement of the throttle. I thought that measurement was what the ECM see's to varify the throttle position.

Ahhh. Yeah I know what you’re talking about now.