I have a 1997 jeep Cherokee xj 4.0 4x4. So here is my issue, when driving it'll accelerate perfectly fine until I hit fourth gear. It changes gears and will only go about 5 km into 4th gear then the throttle will stop. In order for me to go any faster then around 80km I have to drop to third. I had a leaking pump seal so I swapped that and the torque converter along with all three solenoids. I've changed the throttle body to a BBK 62mm with new tps sensor and this problem still persists. I've adjusted the kickdown/tv cable and still nothing. All connections have been cleaned as well. Any help would be appreciated.

 

Any CEL codes?
Has the basic maintenance been done, i.e. spark plugs, wires, cap/rotor, etc?
Have you ever changed the upstream O2 sensor?
Did this suddenly start?
What gear ratio axle do you have?
Do you still have a catalytic converter?

 

Showing no codes and my code reader didn't pick anything up. The motor has been gone through. New upstream and downstream o2 sensors. Stock 3.55 gears. I pulled the tranny because of a bad pump seal and I figured ill throw in a new torque converter and changed the solenoids. This is when I ran into the issue. I swapped all my old part back on and the same problem. Like I said it shifts and accelerates fine until it hits 4th gear, it'll run in 4th until it hits around 83 km then the rpms drop right off and i have no throttle unless I put it to the floor and it goes to third gear.

 

Is the throttle body opening up all the way?

 

The throttle definitely open up all the way in 1,2 and third. I have the cowl intake and I can here it when it's full throttle but just when it hits 4th it doesn't sound like it's taking in any air.

 

http://cruiser54.com/?p=98

 

That's why I asked about the catalytic converter. Do the vacuum test Cruiser posted. Usually when a cat goes you can't get above a certain speed because the engine load is too much for the exhaust system. If your OBD reader shows live data from the engine, you can use it as a vacuum gauge by selecting MAP or Manifold Vacuum. I usually just snap it from full open to closed and watch the MAP signal. If the exhaust isn't too restrictive, the vacuum will go to zero momentarily, then quickly return to its previous value.

 

My entire exhaust is bad so maybe I'll replace all of it. I'll give that test a try, thanks. I'll post back when I replace my exhaust.

 

Well I replaced the entire exhaust system with new 02 sensors and catalytic converter and still having the same problem.