when i first start my 4.o liter it idles fine but when you take off from a stop it goes flat then picks up an druns fine only happens when taking off it has all the power it needs just it drops dead when taking off what could it be please help 1989 cherokee pioneer

 

sounds like a bad spot in the tps, I believe that would be the first thing to check.

 

that is on the butterfly vavle for the throttle which sensor would it be

 

When you are looking at the intake, it will be the sensor directly opposite the throttle cable. It is made to detect a range of motion and feeds back constant motion of the throttle for fuel mixture,etc. I believe that yours will require a small bit of adjustment if you replace it but it is rather simple. The old one can be checked without removing it by unplugging the harness and checking resistance as you open the throttle. If it suddenly changes to a high or low number then jumps back, you probably have a bad section in the sensor and need to replace it. A Haynes manual is priceless for thing like this as it tells you how to check several different sensors and how to troubleshoot several things. I know that knowledge is a great thing but so is a guide book!!! Hope that helps with your poblem

 

there are 2 facing you on the trottle body when you look into the engine compartment the left one is the IAC..remove clean and replace....the right on is the tps and is adjustable...are you sure yours in in tolerance?

 

My 89 is doing the exact same thing. PO put a new IAC on it a few months ago, and everyone it selling me TPS should be next to check. I plan to next week, have been working out some other issues on it. One thing at a time... I will post my results though, and please post yours. This seems really common on the Renix models. The first XJ I had years ago was an 87, and it did the same but not as bad. I didn't know much back then and never dealt with it...