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AW4 - Slow acceleration (probably not engine related).

blistovmhz

NAXJA Forum User
Location
Vancouver, BC
Picked up an '00 XJ for the girl (after she blew up her Civic cause never checks oil...).

It of course had a blown 0331 head, so I just let her drive it till it started eating itself.
Swapped out the motor for my 98 long block (mated to a manual before, but swapping on the 00 AW4).
The 98 long block had the pilot bearing and spacer removed, and I stuck the 00 intake/sensors, and oil pressure sensor onto the 98 LB. Fired right up with no problems other than a bad O2 sensor (taken from the 00, had coolant all over it, swapped it out with a spare from my 98).

The 98 has a moderate cam. The only reason I pulled it from my DD was because I thought it was getting weak, and I used that as an excuse to throw in a 5.3L. Turns out however, I weighed my Jeep for the first time after doing the 5.3 swap and discovered I was 5000lbs, which probably explains why the 4.0L felt a touch sluggish.

Either way, I've got the 98 motor in the 00 XJ now, but it feels just as slow as the 00 motor did. I've owned and/or driven 3 AW4 XJ's in the past, including a 91 with 31's, and they all felt much peppier than the 00. The 98, when it still had the 4.0L, was pushing 35's, and 5000lbs, and still felt faster than the AW4 driven 00 with the same motor. I feel like there's gotta be a problem with the trans, but can't figure out what. TC doesn't feel like it's slipping more than normal, and I can't feel any clutch/band slippage, though I don't really know what to be looking for.

Any common problems with the AW4 that would cause slow acceleration that I should be looking for?


Summary:
* 98 motor (moderate cam) was mated to an AX15, driving 5000lbs on 35's. Didn't feel like a race car, but certainly wasn't a slouch. Kept up with every other XJ I've run against.
Was getting 17-19mpg highway.

* 00 motor (stock) mated to the AW4, driving a stock 00 XJ, felt sluggish. Swapped the 98 LB with the 00 intake/OP sensor/AW4 trans. Still feels slow. Slower than the 98 did, despite being 2000lbs lighter and with 6" smaller shoes.
Before swap, was getting around 21mpg highway. Haven't had a chance to check again since today will be the first highway test drive.

* 00 brakes aren't dragging, everything looks good mechanically. Just is piggish slow.
 
Didn't feel like the trans was shifting at wonky points. At WOT, it's in first off the line, and doesn't shift till nearly 5000. Still feels slow throughout.
I will give the cable a check to just to be sure.
 
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