[Metal_Slug_Jeep]

So if my Jeep sits for a few minutes at idle, it will sputter and die. I try to rev the engine before it dies but it doesn't help. I have to restart the vehicle and rev the engine quickly to get power. I first thought it was a vacuum leak, but I found no leaks. Are there any diagrams of all the vacuum hoses in case I missed something? Also, sprayed some carb cleaner and nothing as far as sputter.

So I'm thinking I have a bad TPS or IAC sensor? I already cleaned the whole throttle body very well, but I was wondering if there was a way I could diagnose which sensor could be bad, or which it possibly is? I hate to buy one only to have to buy the second one and waste money on the first.. I forget which but one of those sensors is like 70$! Also, I have no check engine light..

If anyone has any ideas for what my idling problem would be, please tell me. Could it be a fuel problem? Sorry, I'm still very new to this..

Thanks.

EDIT: Here's what I've done so far as of 9/2/11

-Checked battery
-Checked possible blown fuse (wasn't blown)
-Replaced spark plugs
-cleaned throttle body and AIC.
-Myself and a mechanic checked for vacuum leak
-Replaced AIC Valve
-Grounds appear ok. No corrosion or anything loose.
-Replaced TPS

OTHER POSSIBILITIES:
-Really small vacuum leak?
-Bad Ground?

EDIT 9/2/11
Ok, so I replaced the TPS and I still have idle issues, HOWEVER, before the Jeep dies, it will catch itself and run like normal... then this will repeat until I turn the engine off. What does this mean then?

 

[JPNinPA]

You cleaned the TB did you remove and clean the IAC. I'd try this first. TPS is usually an issue when above idle.

I assume you had this issue before cleaning teh TB. Correct?

 

[alex211]

Has your battery gone dead lately?

If I jump my jeep or bump start it the engine won't idle until the battery is disconnected and reconnected. Otherwise it will either die when you let off the gas or try to idle around 200 rpms.

 

[JPNinPA]

That is true check your battery connections and all your grounds. When you revv the alternator could produce enough to overcome a dead or poor connection.

Good suggestion alex211

 

[Metal_Slug_Jeep]

Yup, I had problems with this before I cleaned the TB. I cleaned the IAC as well. Could someone explain what the TPS actually does? And my battery has not gone dead lately.

 

[Cuder]

How many miles do you have on the plugs?

 

[JPNinPA]

TPS Throttle position sensor. Tells the PCM how open the butterfly valve is. When they go usually there are flat spots when you step on the pedal and RPMs or MPH do not increase for a small area in pedal movement.


Battery does not have to be dead. Connections could be corroded or loose. A loose battery ground did it for me. I installed lights and removed the battery connections. Never tightened the ground sufficiently until after a week of looking at why the jeep would shutter and shut off.


Be sure the IAC connector is on good and hopefully the o-rings are not pinched when you reinstalled it.

 

[Metal_Slug_Jeep]

Thanks guys. Didn't have much time to do anything today but my battery terminals look ok.. I'll have to find my grounds.. my wires are all wrapped together. I'm going to replace my plugs because I have no idea when they were replaced by the previous owner..

Here's where I'm stumped though.. if I have a bad sensor, shouldn't my check engine light come on?? Also, my jeep runs fine for about two minutes and then it sputters for 10 seconds and dies. Reving the engine won't save it so it's probably not a vacuum leak. Also I noticed when my fan is on (I have a fan switch) it dies faster.. also my fan makes a lot of vibrations.. dunno if this means anything at all..

 

[WarPig7]

My 98 TJ did the same thing. Sometimes it would idle fine, later it would idle low and very rough. That is where the fibration comes into play, from the low rough idle. A local mechanic told me it was the TPS. I also did not have the check engine light on. I have not changed it since I completely disassembled my Jeep. Good luck.

 

[mightydog78]

they sell a TPS on RockAuto.com for $25 for a 1999 wrangler. Doesn't this seem scary cheap to anyone?

 

[WarPig7]

Thats really cheap compared to $70-$90. To good to be tru?

 

[afaletto]

Use an ohm meter to check resistance on the tps from open to close. Numbers should change gradually with no random (short circuit) numbers. See utube for video how. That will definately rule on the tps. Sorry replied on phone so no link for you.

 

[mightydog78]

Use an ohm meter to check resistance on the tps from open to close. Numbers should change gradually with no random (short circuit) numbers. See utube for video how. That will definately rule on the tps. Sorry replied on phone so no link for you.

can you do that without splicing the wires?

checking the voltage would actually be more accurate since the variations are more profound than the resistance

 

[oldmots]

This problem is possibly a coked up or defective idle air valve. This valve lets air bypass the closed throttle plate at idle in a controlled way (this part is often called a stepper motor and regulates only air flow at idle). When the throttle plate opens up, the engine gets plenty of air and runs fine, until the throttle closes again.

 

[Jonny Jeep]

The symptoms seem the same as when the upstream heater circuit goes bad on 97-99 models. You have an O2 heater fuse in your PDC which may have blown. Fuse 16 (15 Amp). If it's blown I'd check the wires on the sensors and make sure they haven't been damaged and are shorting out.

 

[afaletto]

can you do that without splicing the wires?

checking the voltage would actually be more accurate since the variations are more profound than the resistance

Your 100% right. Don't know why I said resistance. Easiest to check by pulling the tb. 5 min job. Put leads right to the tps pins once disconnected.

 

[Metal_Slug_Jeep]

Thanks guys! So here's what I've done so far, but there's still an idle issue.:

-Checked battery
-Checked possible blown fuse (wasn't blown)
-Replaced spark plugs
-cleaned throttle body and IAC.

What I'm going to do tomorrow in this order:
-Check TPS with a voltometer
-Replace TPS if necessary
-Replace IAC if necessary

 

[Metal_Slug_Jeep]

Replaced AIC valve today.. no help. Just wasted $90.

 

[tangofox007]

It might be worthwhile to check the resistance in the ground side of the TPS circuit. Excessive resistance there will distort the TPS signal to the PCM.

 

[Metal_Slug_Jeep]

It might be worthwhile to check the resistance in the ground side of the TPS circuit. Excessive resistance there will distort the TPS signal to the PCM.

The next thing on my list is to test the TPSensor with a voltometer and possibly change it. But what do you mean "resistance"? Sorry, novice mechanic.