I thinki you should take the TPS off of the throttle (unbolt it) and test it in your hands - so you can push the lever (tang?) and see if the voltage changes - if it doesn't cooperate TAKE IT BACK and get a new one.


---> I'm also having issues, but it's more complicated ...

when I adjust mine correctly - 0.81V +/- ... 4.9V in, slight resistance to ground (<5 Ohm, maybe 2Ohm?)
I get the high idle, so I backed it off until that drops to ~800rpm (+/-)
now - when warm at cruzing speed, it doesn't want to speed up a little - I have to push the throttle down enough to shift the trans, and it usually or often ****s 2 gears instead of just 1 causing it to rev real high (near 4000?)
so is this the TPS, or Engine Computer, or ...?

 

4000 is nothing for a 4.0 BTW. It is not the ECU.

Do you have your Power/Comfort switch set in Comfort? Is the 7.5 amp "trans" fuse in the fusebox blown?

 

- thanks for the reply

4000 + ...feels too high for going 25MPH just to speed up 5 or 10MPH, but it doesnt always do this - more often when fully warmed up - longer drives..?
- Trans Switch is in Power mode, so it will shift sooner - less sputter and mini backfire - it seems worse in Comfort mode.
- Fuse is good, there was slight corrosion, that i just cleaned off and coated with Ox-gard (improves connectivity & oxidation resistance)

I suspect this is why I got a good deal on the XJ. The TPS is an after-market, I think the last PO put is on.

 

Power mode shifts LATER, not sooner. Ever done my Tip # 10?

Or #1 for that matter? Read #1 and see what is affected by the engine dipstick ground stud.

 

No, I meant shift sooner - when I step on the gas, kick-down. easier down-shift, ..and later upshift.

I did the engine dipstick ground refresh pretty good less than 6 months ago, and coated it when done (don't remember exactly what with - something to stop the corrosion maybe ox-gard?)

I had unplugged the trans computer / fuse and cleaned ... maybe not cleaned real well- it's been a bit longer for that - couple years?
I will recheck now, along with the trans dipstick

 

Don't neglect tip 10.

 

I fought this issue a few days ago. My experience was quite similar. When I dialed the TPS to read 0.83 v, (17% of 4.9v) it resulted in a super fast startup idle of 2500 rpm. I carefully backed the dial back down to .55 v, a little bit at a time and tested each time, and have found the best performance there.

I suspect that my cheapo HF multimeter is not sensitive enough to accurately display lower than a 1v resolution. As all these sensors are reliant on each other, there may also be some remaining issue with some other component.

Since it is running pretty well now, I am just gonna leave it be. If it was someone else's vehicle, I'd probably be more diligent.

Since it is pretty easy to adjust the TPS, you might just try different voltages and see which works best for you.

 

Also remember that there are 2 totally different parts of your TPS:
The engine Side and the Trans side. They work opposite.

 

great if that works - mine sputters when i set it at .55V - had to turn down to .2something to get the idle down
Now I'm wondering if it had self-adjusted to the wrong setting ???
Maybe I need to unplug the battery to reset the computer?

yeah, I think they are both working against me...
So does it down shift sooner & up-shift later when advanced or retarded (lower volts or higher??)

At this point I just want to know if my TPS is bad (before I go blow money I need for other stuff)
Is there a way to just test it without the engine?

 

The TPS sensor works in conjunction with a few other sensors and are interdependent. You might have had the TPS adjusted properly but revealed the weakness in another.

The TPS is a very simple device. It is just a variable resistor, a potentiometer. About 5v in and just a portion of that out, scaling up with throttle movement.

If you can't get it running right by adjusting the TPS little bits at a time and testing it, then it is either defective or not the actual problem. Autozone and many other parts shops will let you return stuff if you don't tear it up.....

 

If you want to save money and diagnose the actual problem before trying a bunch of new parts, consider watching this video and its sequel. He explains how it works as a system with the other sensors so you can more accurately and easily determine what is really at fault.

 

yeah, I think they are both working against me...
So does it down shift sooner & up-shift later when advanced or retarded (lower volts or higher??)

At this point I just want to know if my TPS is bad (before I go blow money I need for other stuff)

Also, that video ^ says it could also be the MAP sensor ...

 

The trans side of the TPS is much less sensitive than the engine side. Test each per my instructions and see if you see issues.

As an example, set the TPS on the Engine side and then test the trans side.

 

Ok,
I bought a brand new NAPA TPS, tested it compared to old one (resistance engine and trans sides, and range of motion with resistance) the new NAPA brand had just a bit more range from max to minimum resistance (nothing that would really matter once adjusted).
I installed the new one & test drove it -- NO change!

So .../. I unplugged the intake air temp sensor - that made it all worse. More difficulty speeding up - more mini-backfiring, more hesitation & sputtering.

Also - I put a spacer in the cable that goes to the transmission from the Throttle body -- that seemed to help - a little bit.

WHAT causes it to sputter, hesitate, mini-backfire and change speed while I hold the gas peddle steady?

H E L P ?

 

Ok
For anyone reading this:

My problem had nothing to do with the TPS! - NOTHING

Seems to be the EGR and other vacuum hoses ...Crank case vent..?

blew it all out with air hose - Runs GREAT now

I do think I need to R&R (and clean) the head cover, along with all the air fittings on it.