Throttle Position Sensor - Sporadic idle issues
 

Hello all!
First off so grateful for this forum! It has been a while since my last post but I still have my jeep and I'm still working on it ;) but that's the fun part!

Alright so, I've always had on again off again sporadic idle issues with my 99 sport. I've cleaned everything in the throttle body and I'm focusing in on the TPS. I replaced it when i first bought the thing back somewhere in 2018 but I've never really had a great idle and I know there's alot of reasons why that could be. I've done alot of different work on it that has improved the overall driving but the startup/idle still remains the spot I can't quite nail down.

Anyways to get to the point, I backprobed it with my multimeter and from what I've heard you turn the ignition ON and slowly open the butterfly valve and see if the volts increase gradually or if there are some spots where the voltage jumps around indicating a bad TPS. It's supposed to start somewhere around a volt and work it's way to around 4volts increasing smoothly. But when I do the test before even touching it the voltage is jumping around all over the place from 1 volt all the way to 3 volts. When I do start slowly opening the butterfly it acts normal starting at a little less then a volt and goes all the way to 4 without jumping around.

My question, is this also indicating a bad tps or is there something else at play here?
I was thinking about it today when i started my jeep. It always idles super high going up and down but if i just barely touch the pedal not even pushing it down it jumps down.

I already got a new TPS in the mail but I wanted to bring it up and see what yall thought.

Thank you!

I have a 99. My TPS tested fine and it was still bad. I had the same issue with a high idle on start up.
I could feel it surge while coasting and occasionally it would shut off while stopped in gear.
A mopar TPS fixed the issue.

Most likely a bad TPS.

You tested it and found it was defective so replace it. BTW, it's great to know someone who gets out his VOM out BEFORE buying parts!

Heck, I test the new parts too! I see too many people fire the parts canon and end up replacing a good sensor with a bad or poor quality new one. Then they're stuck thinking, "I just replaced it, so that can't be the problem."

Wise man! Parts quality is getting more "variable" every year :(

Got the new TPS installed and tested 😎 👌

She is purrring nicely! Seriously, this is the best idle I've ever had! :whistling2:

That was the problem. And yes I think this is a good example of poor quality parts.

Thanks everybody!

Just to add to this for anyone looking.
I had a similar problem with mine and it turned out to be the distributor cap. The guy I bought mine from was a coworker and said he installed a cap with brass contacts. Turns out it was just the rotor that was brass. I ordered a brass cap and cleaned the contacts on the aluminum cap with a diamond file and it runs flawlessly now.

Don't buy dist. caps with aluminum contacts, ever! They will give you problems sooner rather than later. An old brass cap is still better than a new aluminum one IMHO.