keelwheel

So, I have a 96 xj sport 4.0 inline six A.T. with 200,xxx mi. While on a trip last week, my xj kept wanting to downshift into 3rd when reaching 65-70 mph. Going downhill seemed to be ok, but going uphill or even a slight load at higher speeds caused a lack of power (doesn't seem to want to rev. above 3,000 rpm or so) and would cause it to downshift.(again, no additional pull past 3,00 rpm or so.) I am told a bad cat. converter could be the problem. It does need to be replaced, getting recall voucher from prev. owner soon. It runns ok in first and second gear, good pull. problem seems to be only at higher speeds. Any Ideas would be greatly appreciated!!!

Slick761

Do you have stock tires?

keelwheel

yes, tires are stock size I believe.

93gc40

Sounds like a couple issues at the same time. Tire size?? Is trans fluid GOOD? Recent change in MPG? The downshift sound normal-ish the issues at 3000 don't.

93gc40

"I Believe" is not valid. Are they 215/75-15 or 225/75-15?

keelwheel

to my knowledge, there are no aftermarket mods on this jeep. Im not getting any check/service lights either.

keelwheel

Ahhh...the tires are actually 235's sorry!

keelwheel

Gas mpg is lousy as well. when I bought it, it only got 10-11 mpg. I put new plugs and wires in and now get 12-13 mpg. if that helps...

Slick761

You definitely have something more then tire size going on... how good of a wrench are you?

keelwheel

on a scale of 1-10, Im around 4.5 on the wrench scale.

shoobyd

If fluid is at the right level and clean, try adjusting your kickdown cable.

From there, it could possibly be a bad TPS, a bad TCU, or faulty shift solenoids.

I'm at the the solenoid replacement level myself, which I will be tackling this weekend.

I'll let you know how it goes.

keelwheel

thanks, Ill keep an eye on your progress!

keelwheel

when getting up to 60-70 mph, it kicks into 3rd and really struggles to go back into OD. I have to really feather the gas to make it upshift. when it downshifts, It wont go much over 50mph or so. when it finally upshifts, it will again downshift with even the slightest acceleration.

keelwheel

It drives and shifts fine city driving, just when I get up to highway speeds do I have the downshift problem. anything over 55-60 mph gives me trouble...

excess650

From the sounds of your fuel mileage, I'm inclined to think your O2 sensor(s) need replaced. Too much fuel means poor mileage and less power.

A clogged CAT will prevent good exhaust flow and make it run hot.