What's your TPS WOT voltage? Jeep 2.5...

Will Carter

Will Carter

Well-Known Member
Joined
Mar 23, 2005
Location
Burlington
1997 Jeep TJ. Been sitting for a few weeks after its last trip out. Seemed to run fine on the way home. Now engine idles rough, backfire through intake, when it does want to acclerate it bogs down at ~2500rpm.

No codes other than the EVAP because it's removed (but it's been running fine without it for months).

I'm at the TPS. What has your WOT voltage output been when you've ACTUALLY measured it. I know what the manual suggests and what everyone on a Jeep forum likes to copy and paste from a repair manual what it should be but with the old and brand new TPS I'm getting a WOT measurement of ~2.9v.

That doesn't seem like it's cutting it...and I guess I'm thinking that maybe since it's still within acceptable range and sweeping cleanly it's not throwing a code yet...?
 
Have you filed your TPS report?
 
Dont know anything abt the voltage but....
mine did the same thing!!! I replaced the sparkplug wires and distributer cap and rotor and it worked fine after that. worth a try
 
Will the refeence voltage should be 5v and the wot should be about that. What voltage are you getting to the tps?
 
You should have 4.5 to 4.8 volts WOT. Need to check with KOEO (key on engine off) voltage on the reference wire from the PCM should 5 volts. I have seen upstream O2 sensor kill the 5v and make a run bad or stumble problem with no codes.
 
Grounds are good. All three of 'em.

TPS has good 5 volt supply. But will only put out 2.9 ish at WOT.

Someone want to go measure theirs?

Again, same result with new and old TPS. All other sensor test perfect and I've even swapped out Crank and Cam positioning sensors to see if there was a change. There was not.


Snappy, the chat box thing was blinking like you sent me a message but I never could get it to show up...
 
OK thats right sorry to sound like I was harrasing you. I will get on Identifix when I get back to the shop and pick there brain...
 
How are you supposed to check fuel pressure on this thing with no pressure port?

Is the fuel pressure regulator supposed to bleed back into the tank? The intank pump holder thing fills up with gas when it's running. If the regulator does not return fuel back into the tank then I'd say the in tank line is leaking...
 
Does this thing have an IAC motor? just thinking when had on a 4.0 that was giving us a fit same syptoms....
 
They do have an IAC, but that doesn't sound like the issue. I'd check my voltage, but my battery is dead. I may throw it on the charger and I could get a voltage for ya, but it'd be tomorrow.
 
Fuel pump was failing...finally found the adapter for the gauge.

Was only running about 35 PSI.

New fuel pump. Now it runs faster and jumps higher.

TPS still reads only 2.9vlts at WOT but I don't care anymore.
 
For tech's sake somebody go check their TPS. Don't have to take it off the throttle body. Just poke the wires with the lead. The middle wire.
 
Hey Bro. I just looked up our dealer tech manual to verify. You should 100%, most certainly, have right at 4.8 volts wide open throttle.
You have one 5v wire, 1 ground circuit and one reference wire. You said the resistance was good on the ground wire, but you need to verify that it is capable of carrying an electrical load. Load test the circuit or just simply run an auxillary ground off the TP directly to ground.
Call me if ya need to, Im a 13 year driveability tech at my local Jeep dealer. More than happy to help ya out.
 
Jody Treadway said:
Hey Bro. I just looked up our dealer tech manual to verify. You should 100%, most certainly, have right at 4.8 volts wide open throttle.
You have one 5v wire, 1 ground circuit and one reference wire. You said the resistance was good on the ground wire, but you need to verify that it is capable of carrying an electrical load. Load test the circuit or just simply run an auxillary ground off the TP directly to ground.
Call me if ya need to, Im a 13 year driveability tech at my local Jeep dealer. More than happy to help ya out.
Click to expand...
Just to be clear...this is while attached to the throttle body? I can get it to go to high 4's when off but it has a lot more travel than the throttle body would allow.
Thanks. I'll stick a ground on it and try.
 
Indy Will said:
Just to be clear...this is while attached to the throttle body? I can get it to go to high 4's when off but it has a lot more travel than the throttle body would allow.
Thanks. I'll stick a ground on it and try.
Click to expand...

Key on, engine off, hook up a DVOM DC volts, measure voltage on the orange wire-should be right at 5v. Then measure voltage on the orange/dark blue wire (this is the signal wire back to the PCM) with the throttle closed-should be around 1 volt(ish), keep watching the voltage as you sweep the throttle open, it should smoothly climb to approx 4.8 WOT. Take note where you are getting your ground from. Compare the readings with the ground probe on the battery or by probing the ground circuit at the TPS. This will allow you to see how good the TP ground circuit is.
If your voltage is still too low at WOT, do you have more "sweep" left in the TP that the throttle body is not allowing? Maybe the TP is incorrectly installed in the TB?
Holler back, I'll help all I can
 
Still sitting at a 2.9 WOT.

There's no other way it can mount.

All three TPS's i've messed with have a clean sweep to 4 ish when not mounted and are allowed to turn their full capable range. When mounted to the TB they all get stopped at 2.9-3.0 because that's all the TB can turn.

No change with an auxiliary ground.
 
Indy Will said:
Still sitting at a 2.9 WOT.
There's no other way it can mount.
All three TPS's i've messed with have a clean sweep to 4 ish when not mounted and are allowed to turn their full capable range. When mounted to the TB they all get stopped at 2.9-3.0 because that's all the TB can turn.
No change with an auxiliary ground.
Click to expand...

There is a early build and late build 97 TPS. Any chance that you have the wrong one?
Early build TP's are-Pin 1-supply, pin2 -signal, pin 3-ground
Late build TP's are- Pin 1 ground, pin 2- signal, pin 3- supply
 
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