mntn-biker

Does the check engine light need to be on to throw a code saying the throttle position sensor is bad? I'm just throwing out a WAG that I have a bad throttle position sensor. I have a 2000 XJ 4.0L that all of a sudden, it wants to idle 200-400 rpm and will sometimes stall at a light/stop sign, etc. It has plenty of power and will take right off but after this weekend, I get the low idle thing going on. I asked Advance Auto Parts to throw their scanner on it but they asked if I had a check engine light on which I do not.

tjwalker

Not all symptoms will set a code.

If I were you I would concentrate on two circuits.

1. The IDLE AIR CIRCUIT. Start by cleaning both the idle air control and the throttle body. Info on that below.

2. The throttle position sensor can be tested and testing should be done before condemning the TPS.


The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality

99xj1

I've had two TPS sensors go on two different Jeeps without the engine light coming on.

Bustedback

Replace the Idle Air Control motor, problem solved.

mntn-biker

Thanks for all of the info everyone!!! I went and bought a $4 can of throttle body cleaner and sprayed it around inside the throttle body thinking this would be the cheapest troubleshoot. I put everything back together and it seems to be idling like it was prior to tonite's low idle episode. I think I will take tjwalker's advice and clean the IAC since it is not that big of a job to take things back apart.

Gotta love this forum!!!

Thanks again everyone!!!

Mike

diehl2u

I have 2000 4.0 Jeep with the same idle issues...(low idle at stops and stalls) Came across this thread and went to advanced auto for idle air control motor . Just changed it out and when I installed it and started back up it had a higher then normal idle for a few minutes then drove it down the road and then at my third stop sign it stalled... Help lol... Getting tired of two footing it at lights and stops...

juiceortiz

I bought our Jeep with 203,000 mi. It had a rebuilt motor which only had about 30,000 mi on it. At about 210,000 mi, it started hesitating every once in a blue moon. A couple weeks ago it started dying on me (4 times in one week). I ordered a new Bosch fuel pump from Rock Auto and installed it this past Saturday. It was about a 3 hr job. (I was going to cut a hole in the bed to access the pump, but I read some reports from others who said it was real easyto drop the tank, and it is!)

Replaced the fuel pump 3 days ago with 241,000 and it is purring for now...

I can post pics if anyone wants.here is the pump I used below:
http://www.rockauto.com/en/moreinfo....sn=378&jsn=378

p.s.-the OE sock was smaller and black/brown with sludge inside. The Bosch pump comes all-inclusive and with a bigger sock.

juiceortiz

I started having problems several.days after replacing the fuel pump. Finally think I found the problem: Camshaft Position Sensors and Crankshaft Position Sensor.
I would highly recommend changing the before a computer. If those are bad and you install a new computer, the same problem will continue.
(I had a lot of recommendations say g that the computer was bad, I would recommend that option last me a last)

DFlintstone

Glad you got it! A thread from 2011, you might or might not hear from those guys though!