Short story: In laws have a 99 XJ that wasn't in the best of shape. I had a 99 XJ. I fixed it up and gave it to them as it was in "better shape". Fast forward about 5 years... Wife had to chauffeur them around and drove both XJ's. She told me the folksXJ made more power by a long shot than the one we gave them. Oh yeah, as well as being the same year, both XJ's have about 215K miles now. Is there a reason why one would have more power than the other? Plugged catalytic? Some tuning issue? Anything else I should be looking at? Didn't find much in search on an issue like this, though it's quite possible I'm terrible in the "proper words for a search" department. If you have links to other threads, it'd be great. Thanks in advance.

 

Are you able to test drive both of them yourself?

Is the CEL on?

If you have a code scanner with live data, you can check both and compare.

 

Like said above you need to drive both of them yourself. If there is a real difference then start going through all the normal "tuneup" stuff.
One thing that immediately comes to mind is that if
​​​​​​they are both automatic transmission that would affect the perceived power is the TV cable adjustment......and the throttle cable.

 

I haven't been able to drive them, but the wife did. She pretty much drove them side by side and it was obvious to her enough that she made the comment. She's a leadfoot, so I believe her (not to mention I always thought ours was a bit lacking in the power dept).
Nope, no CEL on. I've had an OBD tester on my 99 when I was having a TPS issue (which kicked a code), but I didn't see anything else pop up.
I made a major move recently and most of my stuff is buried in a conex, so it might be a bit before I can find it.

 

OK, so that's something that's never crossed my mind...and, yes, both autos. The TV and maybe throttle cable adjustment might be a thing, Just not sure how to do it. I can try to search the threads, but if any of you have a ready thread link handy...or better yet, a quick reply if it's easy? Thanks.

 

Same differential gear ratios?

 

1) no one is doubting your wife noticed a difference, it's just that if you're the one that needs to fix whatever needs to be fixed it would be easier if you drove them.

2) Google adjusting jeep xj TV cable, it would be faster than trying to explain it. It takes about 15 seconds.

3) and do, it takes 2 people, make sure that when the throttle pedal is floored the throttle on the throttle body is all the way open

 

Same differential gear ratios?

Not positive, but I won't assume thought both are stock. Good point...

 

Will do in the next day or so to check the TV cable. Yeah, it might be a bit before I can drive the other one as it's now about 4 hrs away... I'll do the google college of knowledge and track a video down for the TV cable. Thanks.

 

And if the slow one has giant tires and the other one doesn't, that would matter.

Are they both 4wd?

 

Sorry, I left that out. Yes, both are 4x4, and both sets of tires are your average 235/75/15's. The only difference I can see is one is a Sport and the other is a Limited...

 

 

This thread (2 more or less identical XJ's, no obvious problems, one may be faster) is interesting... ąt least more interesting than the usual " I just got my first XJ, it won't start, what should I do?"

So the big problem is how do you fix something when you don't really know it's broken.
some really basic stuff.
Are you driving them ąt the same elevation? If the fast one lives at 500' and the slow one at 5000' problem solved

Is one Fed and the other CA? Don't know how much difference it would make but it's a variable.

Do they have same thermostat?

Then, after the easy stuff like the TV adjustment and making sure the floor mat isn't under the accelerator pedal, and a really good tune up if you're still convinced there's a difference start with some real diagnostics... fuel pressure, compression come to mind
You mentioned plugged catalyst, vacuum gauge could help with that diagnostic

 

plus 1 on the floor mat Take the mat out and reset the tv cable

 

@exasemech Dang, you brought up a couple of things I never even thought of, like the thermostat temp.
Yes, both driven at same altitude (8K feet-5K), Both Fed. Did the TV adjustment and it made a huge difference (see reply below).
Can you tell me how to check for a plugged catalyst with a vacuum gauge? Don't think I know how.
Thanks.