Hello all, I had rough idle, surging rpm at certain throttle settings issues, and after looking here I found out it's the TPS. To confirm, I disconnected the TPS and it ran without those issues. So I decided to diagnose it. On the S4 I used the bottom of this FSM page to help me set it.

Well, I found out that A->B is supposed to show 1k idle 5k WOT. It in fact shows me 5k idle and 1k WOT... So I decided to check A->C and it's supposed to be around 5k always. That shows me... 1k idle 5k WOT. I took the screw and messed with it seeing if it would change anything. It goes to 1k at idle if I screw it out so much that the screw almost falls out. But in that case going to WOT gives me 0.5k. Somehow it's giving me less resistance at WOT than idle. The other connection should not change but it's sweeping. Is there a chance this could be wired wrong or something? Or do I need a completely new TPS? Thanks!

 

As long as you are disconnected from the circuit and know that your meter is functioning correctly. It does seem to be out of spec.

1k is with no pressure on the throttle besides the spring. Put your test leads together and verify zero or very close to it. If you have any known good resistors around, check your meter with those. They are usually within 5-10% accurate.

 

Hi all, an update. I got a brand new TPS and now I am having the same exact issue. To reiterate, at idle it shows me a high resistance and at WOT it's showing a low resistance.

Idle:

WOT (lowest it goes to there is 0.28)

This is the A-B connector in the FSM, screenshot from the original post. This is with the plug disconnected of course.
As for A-C, same story as original post, it's showing me what seemingly should show at A-B, low resistance at idle and high at WOT, when it should show it around 5000. Changing the screw changes the range a little but it's still completely wrong as described. I can't see any way this could be wrong, I measured and remeasured but it's still showing this. I need a sanity check lol.
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​​Extra info: most of emissions removed, no air pump bac or even the accelerated warmup system. No difference doing this test hot or cold engine either.

 

This is also a long shot, but I have to ask - is the TPS plunger supposed to be fully out at WOT and compressed at idle? Video attached of that. That's the one singular thing I can think of, it interacting wrong with the throttle linkage.

 

I tried to explain this before in my last post and will try to do better this time. WOT means Wide Open Throttle. With your accelerator pedal to the floor, that is wide open throttle or spring fully compressed. No tension on the spring is the 1v reading that you should be adjusting to.

 

Jeff, that's what I'm trying to do. I was doing the resistance method shown in the FSM initially. No pressure on the pedal, not touching it, I'm getting 3-4k resistance. With the pedal to the floor, spring compressed, it's getting me 0.25k resistance. I just tried the voltage method as well - using the A-B connections. Idle is showing me 3.7 volts and at full throttle, compressed spring, it shows 0.08 volts. I cannot see what I'm doing wrong personally.

 

Your test leads are connected wrong.... I think. The drawing shows the connector disconnected looking from the inside. You can see the blade? terminals. Straight and narrow.

Switch your test lead to the other side of the connector.

 

When the factory service manual references pins, it's from the rear view.

 

Guys, I feel really silly now. Yeah, it makes sense how what I thought was A-C was showing me the seemingly correct reading while the other was showing the reverse... Thank you! I could have sworn I read a write up and probed the correct color wires... oh well, **** happens! Doesn't explain why the other connectors were showing me such a difference when it should show 5-5 idle to WOT, but honestly I'm not gonna worry about that

 

Yeah! That fixed it lol, no more hesitation and surging. Perfect. Now to find the vacuum leaks lol