my new MJ...HELP!!!!

[boogie94xj]

I recently acquired an 88 MJ. The engine seems to miss and backfire in the same throttle position regardless of what gear I am in. Not bad in 1&2 but 3-5 is really rough. If I back off the throttle or get into it a little more the problem goes away except in 5th gear. Since the problem happens in the same pedal position in every gear I was thinking bad throttle position sensor. Does this sound right to any of you engine guru's? Anything else I should look into?

[RichP]

Could be, and sounds like a tps but seeing as how this is a newly acquired vehicle I'd do the following first.
1. Complete tune up, plugs, wires, cap, rotor.
Make sure the correct plugs are hooked up to the correct nipples on the cap.
2. Clean the fuel system and throttle body with a good cleaner, dump a large bottle of Chevron Techron in the tank.
3. Then do the TPS.
This is not associate with the problem but...
4. Change all the fuids, all of them, clean and backflush the cooling system. Refill with coolant and distilled water. Might want to even do the tstat, check the pressure tank and cap.

[boogie94xj]

I did al the fluids and a tune-up on the new girlfriend as soon as I got her home. Acted like a virgin on prom night. All nervous and gittery and now she purrs like a kitten but the throttle issue persists.

[Kejtar]

hmmm.... be carefull what you do and where with your "new girlfriend" so that you do not get arrested and cited :D
Kejtar

[Pete M]

Is there fresh gas in the tank? Mine stuttered at partial throttle when I first fired her up after she sat for a while. (almost 2 years!) I drained most of the stale gas and replaced it with fresh stuff and a whole bunch of octane boost. Now she runs like a top!
Jeep on!
--Pete