Marvinator

My jeep is a 1999 Jeep Cherokee 4.0L inl 6.

When it come to working on cars, I'm about an intermediate. I can replace most parts (sometimes with help.) Some time ago, I was told that the car would need a new Throttle Position Sensor. After many months of low funds, we finally got to the point where I can purchase parts and install. Ok, so 4 days ago I got the part installed. The Jeep would start (rough, but it has been sitting a long time) but when let off the gas, the engine dies. I had thought it was how I aligned the TPS on the carb. The 'tang' would not go in the TPS, so I angled it about 22.5 degrees counter clockwise, facing the engine , to get it to connect. (The only instructions I could find on this was a video where the guy says "take care to align the sensor with the socket tab on the throttle shaft.")

Next, today I took off the TPS and angled opposite to where it was. The engine starts, but the idle is very fast and goes up and down and up and down quickly. I'm going to guess I had it aligned properly before, but what to do about this. I'm at a loss. I'm thinking that the IAC may also need replacing... the video suggests replacing them together. I have no idea.

I posted this problem once before and got no responses. I'm hoping for better this time.

cruiser54

If you still have the old TPS, reinstall it.
Make sure your intake manifold bolts haven't loosened up.

Clean your throttle body and IAC. CRUISER'S MOSTLY RENIX TIPS

THROTTLE BODY AND IAC CLEANING

OCTOBER 30, 2015 SALAD 24 COMMENTS
Originally by TJWalker of CherokeeForum & JeepForum



The Idle Air Control (IAC) is mounted on the back of the throttle body (front for ’87-’90).

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 retracted, the air control passage flows more air which raises the idle speed. When the valve plunger is extended, 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. This should be part of a normal tune-up procedure and whenever idle/stalling issues are present.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

1. 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). On ’91 and later, it may be easier to just remove the whole throttle body. Be sure to use a new throttle body to manifold gasket when reinstalling.
2. “Gently” wiggle out the IAC from the throttle body. Gasket/O-ring on the IAC can be re-used if it is not damaged
3. 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 oxygen sensors. 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.
4. Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner.
5. It is also a good idea to clean the entire throttle body bore itself, the butterfly valve inside of the throttle body and it’s edges, and all associated linkage as long as you have things disassembled.

Revised 1-31-2016

Marvinator

Thanks. I had already resigned to cleaning the IAC. All put back together and now it runs so much better.

Rogue4x4

We love updates with success stories, awesome!