I have a 1997 XJ that I have done a full tune up on and has been running great so far. In that last few days its been dropping rpm when I accelerate at higher speeds. When I am cruising past 50mph and I press on the gas the rpm will go up and then drop about 500rpm. It usually happens around 2000 and 2500 rpm then it would drop down close to 1500rpm, and it will feel like it has little power. If I press that gas a little harder it will down shift and then it goes like regulars.It only happens in 3rd or 4th gear. I have no check engines lights and for the most part the truck runs great.

 

just guessing.....

you might want to disconnect the battery and let the ECU retrain now you did so many changes like a tuneup. After 30 or so miles, see if it still does it.

 

What you are experiencing sounds about right. That is about the area that the torque converter cuts in, from what I am told. On my car if you are cruising at 65 mph the RPM should read 2000-2150 if it is reading around 2500 RPMs at just cruising then the torque converter is not kicking in and your gas mileage will show it. I replaced my neutral safety switch and this went away ... so far.

If my example RPMS check out and it stays stable and does not jump around then no issues.

BTW mine is a 2WD.

 

Its 4.0L 4WD. What does neutral safety switch do? I did have some injector problems that caused misfires and fouled plugs but that has been fixed.When I fixed those problems I did disconnect the positive for the retrain and then this started. Wonder if that has anything to do with it. Thanks for the replys so far.

 

Neutral Safety switch lets you start the car in neutral and park ... not in Drive or Reverse.

 

under normal acceleration the torque converter will lock up at around 45mph, the engine speed will drop around 500rpm. The more gas you give it, the longer you delay the tc lockup. When it is locked up and you give it more gas, it will unlock, downshift, and take off, when you let off, it will lock up again.

 

Thanks for all the info. I just bought this Jeep a month ago and still getting used to how it works. Thanks for the info on the neutral safety switch. That helps a lot and and I am going to clean it because sometimes my truck will no start at all and I have to wiggle the shift lever before it starts. Thank you for the responses.