1g Bad TPS???

[MALaCasse]

I tested my TPS on my 1991 TSI today and everything checked out good except for the TPS pins 2 and 4 resistance check. It read 1.1k ohms with the throttle closed and gradually increased to 1.9k ohms. It then read open from 1.9k ohms up to 2.4k ohms (about half throttle). It increased normally from 2.4k ohms to 5k ohms. Does that open indicate a bad TPS?

^^^Those readings were taken as I was opening the throttle.

Anyone?

 

[Soccerguy136]

Did you make sure to follow this guide:

TPS Adjustment

Did you do any adjusting after it failed, such as loosening the two philips screws and attempting to set the closed voltage to .9K as opposed to 1.1k that you saw?

 

[MALaCasse]

I did not do any adjustments. I have a few boost leaks that I need to take care of before adjusting anything. In the meantime I have been function checking various components just so I'm ahead later down the road. I just want to know if the open that was displayed at half throttle indicates a bad TPS. Thank you for your reply. Hope you have something for me. If I'm an idiot let me know

 

[Soccerguy136]

You are certainly not an idiot. The simple fact that you are doing preventative maintenance and function checking components proves that.

As for your numbers. I'm still having some trouble verifying what your readings were.

Did you check it on or off the car?

If it read 1.9k ohms with the throttle closed, that is definitely out of spec. It should read at least below 1k ohms with the throttle closed.

By open, do you mean infinite continuity?

If you only checked it once, I would guess that you may have slightly moved off one of the pins with your tester leads. Unless you were using alligator clips, in which case disregard.

It seems like you need to get the throttle closed ohms in spec first and then recheck.

You set this by loosening the two screws, having the throttle closed, have the tester leads/clips on pins 2 and 4, and moving/rotating the tps sensor slightly until resistance is <1k oms. Once you have that, screw it down and then retest everything else.

One last tip, make sure the negative goes to 4 . It happens to all of us.

Let me know how it goes.

 

[MALaCasse]

By "open" I mean no continuity.

The TPS read 1.1k ohms (a little high) with the throttle closed.

As I opened the throttle it smoothly increased to 1.9k ohms.

As I opened the throttle more it showed that there was no continuity between 1.9 and 2.4k ohms.

As I proceeded to fully open the throttle is smoothly increased from 2.4k to 5k ohms.

I tested it probably 5 or 6 times using alligator clips with the same result. I am not sure that I had the positive on 2 or 4. I will test it again in a bit. Will that make a difference? Isn't the TPS just a series of resistors? I will upload a video of my next test to make it more clear. Thank you for the help.

My multimeter took a crap on me. I'll pick up another tomorrow and re-test. My initial high idle problem is fixed. Added coolant stupid temp sensor.

 

[steve]

If the resistance doesn't smoothly change as the throttle opening changes then it's bad and in need of replacement.

The VFAQ isn't telling you the whole story when it comes to setting the TPS.
The FSM states the standard value range for the resistance between pins 1 and 4 are 3.5k to 6.5k ohms.

This range for the total resistance of the TPS has a direct effect on the resistance setting at the closed throttle position in order to get the factory specified 0.48 to 0.52 volt output with a nominal 5.0v input to pin 1. Read up on voltage dividers if you want to understand why.

 

[MALaCasse]

If the resistance doesn't smoothly change as the throttle opening changes then it's bad and in need of replacement.

The VFAQ isn't telling you the whole story when it comes to setting the TPS.
The FSM states the standard value range for the resistance between pins 1 and 4 are 3.5k to 6.5k ohms.

This range for the total resistance of the TPS has a direct effect on the resistance setting at the closed throttle position in order to get the factory specified 0.48 to 0.52 volt output with a nominal 5.0v input to pin 1. Read up on voltage dividers if you want to understand why.

I have been reading non stop for the last two weeks. I'll add that to the list. My resistance between pin 1and 4 was 5k ohms. That's right in the middle so should be good correct? Thank you for the input. And I will read up on that.

 

[steve]

My resistance between pin 1and 4 was 5k ohms. That's right in the middle so should be good correct?

That means it passes one of the tests. Sounds like it fails the "resistance changes smoothly as the position is changed" test. It has dropouts and discontinuities.

Those will cause erratic performance and throw TPS faults.

 

[MALaCasse]

I've been driving the Talon for 2 weeks now and the TPS has not been causing any problems. Could have been my crap multimeter. I'll check it once I get a better one.

 

[steve]

Could be. Do you have any way to datalog?

 

[MALaCasse]

I will once I download Jackal and get back home.