Excellent forum Hello to all, This is my first post..

Hello, I have a 1996 Jeep Cherokee XJ. It's on dual fuel, LPG and gasoline.
When running on LPG it runs fine, but when it's running on gasoline it's jerky, like it's lacking fuel, it does this about 20 minutes into driving the car, I have had it at a Jeep service Center 3 times and it's not giving any codes. They say everything is normal. I have noticed the idle counter needle dips rather quickly sometimes, goes down to about 100 rpm and then goes back to normal when I am about to stop. Anyone have any suggestions to point me in the right direct..

 

I would do a fuel pressure test. There is no code for that.

 

Thanks cruiser54, a fuel pressure test was done, all normal.

 

Have you ever cleaned the throttle body and IAC?

Courtesy of TJWalker:
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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

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.

“Gently” wiggle out the IAC from the throttle body. Gasket/O-ring 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 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.

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 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 10-6-2014

 

Thanks cruiser54,your knowledge of Jeeps is impressive.

I'll take a look at what you have suggested over the weekend.