Is the computer in my 90'(4.0,AW4,231) tuneable?

I'm wondering to what extent(if any) the computer in my XJ can be retuned. The reason I'm curious, if it is, I should be able to change the shift points, right? I was helping a buddy out on Saturday with his F350, and he had another guy come by and retune his computer with one of those hand held deals. It made a huge difference, it shifted later(good thing), it had way more low end speed(another good thing), and actually ran a little cooler(a really good thing). He put on new exhaust, a jet chip, bigger tires, new gears, and the retune really brought out the best performance from the engine. Now back to me and my XJ. I'm running 33's(35's sooner than later) 4.10's, and will be doing a cat back with a flowmaster delta II. I'd like all of these changes to perform as well as possible, and retuning the computer would help, wouldn't it? When it comes to the computers on vehicles( or actually any computer) I'm more than a little in the dark, I'm fully on the dark side of the moon, I know nothing. Any info( as always) would be appreciated.

Thanx,
goldxj

as far as I know the jet chip does most of the retuning you cant just retune the computer without a jetchip being installed too
you can get a jetchip for the 4.0 I6 but I dont know off hand what gains you would get
good luck

Bose

The Jetchip only fits the Chrysler computers, and since the XJ used a separate TCU thru '95 the Jetchip won't address shift points anyway.

The '90 used the Renix. Not flash programmable, and no chips. Mopar Performance used to sell a performance ECU to replace the stock one, but it was for race applications only, and has long been out of production. And it was an ECU not a TCU, so it didn't address shift points.

Well, that answers that. Thanx guy's.

Cheers,
goldxj

Eagle said:

The Jetchip only fits the Chrysler computers, and since the XJ used a separate TCU thru '95 the Jetchip won't address shift points anyway.

The '90 used the Renix. Not flash programmable, and no chips. Mopar Performance used to sell a performance ECU to replace the stock one, but it was for race applications only, and has long been out of production. And it was an ECU not a TCU, so it didn't address shift points.

Click to expand...

The TCU is seperate on all 87-01 models with the AW4. It may affect shifting (91-01) because the JET chip modifys the sensor readings like the TPS.

The Renix ECM was at one time modified by JET as a unit. I doubt they do this anymore and as Eagle said the Mopar Performance ECM is no longer available.

How about shifting it manually?

http://www.steve88xj.com/aw4