RevZeroX

Agreed on new thread.

But I'm shooting towards o2 being bad on your ride.

highrollersk5

Just changed the o2 and wouldnt i see sign and notice it running rough also just started thread and your tps can make your jeep shift weird figured that one out thanks

bdf_tech

There are a variety of URLs that describe TPS setup/checking for 4.0L motors (such as www.lunghd.com/Tech_Articles) -- but nowhere can I find any reliable reference to setting up the 2.5L 4-cyl tbi TPS.

Apparently the procedure is a bit like the 4.0L, but reversed (due to being auto tranny with dual connectors). And also the VIN E (1989) procedure is different from the 88 and earlier VIN H 4-cyl (have tried all of these, to no avail).

Even took it to Jeep dealer, they made some passing reference to a "10% setting" -- no idea what they were referring to -- but their setting didn't fix the surging either...

Being so rare (and discontinued by Jeep), the 2.5L TPS part is > $130 cost (special order), so not a swap I can take lightly -- has anyone seen a solid reference to a test procedure anywhere?

Would definitely appreciate even a link or referral -- thanks

alpine.adrenaline

X2, I've set the TPS on my 2.5L according to the 4.0L procedure and it still doesn't seem right (my 4-banger surges too). Any info on the differences would be much appreciated.

dirtbiker117

Sorry guys, I just have info on the 4.0L Maybe someone else knows what to do on the 4 cylinder?

bdf_tech

Well, was able to do some additional research, came up with a procedure that appears to be specifically for 2.5L tbi VIN E. Actually drove to another town where the library has a set of Mitchell manuals; unfortunately, their set did not include Jeep! (?) But the reference people directed me to their internal Alldata site...

Won't try to quote the entire procedure here (probably why Haynes tells you to "have the dealer set it up for you"), but here's the gist of it -- I did try this adjustment on mine last night, but haven't driven a significant distance yet.

They spend about 3 paragraphs describing how to use an "ISA motor exerciser tool" to back out the ISA motor "until the throttle lever contacts the idle stop screw" (on the throttle body). OK...

Well, not having an "ISA motor exerciser", a "DRB II scan tool" (or even a Treadclimber), I decided to take the "cowboy" approach and just unmount the ISA motor. (not too hard, given that you have some little tiny 1/4-in drive sockets on hand, a retrieving magnet, etc.)

Once you get the throttle arm against the stop screw, the rest of the procedure is somewhat similar to the 4.0L:

"Find the 4-way TPS connector, insert the blk lead of the DVM into the back of terminal D. Insert the red lead into the back of terminal A. Note the voltage reading, this is the 'input voltage'." (i.e. the reference 5V)

"Remove the red lead from terminal A and reinstall it into terminal B. Note the voltage reading (this is still with throttle fully closed) across terminals D and B, this reading is the 'output voltage'".

"Divide the output voltage reading by the input voltage reading. The ratio should be between .925 and .935 (.930 optimum)."


For example, on my XJ the 'input voltage' was 4.68V, 'output voltage' was 4.43, for a ratio of .946, so then I adjusted it to 4.35V, which makes the ratio .930 (give or take a bit). Now, this is a bit of an encouragement to DIY Jeep guys, as I had been adjusting the TPS to where it "ran well"; this apparently got me within .015 of the correct ratio...

I never paid much attention to alldata, really, unless you're looking for a TSB or something like that -- but in this case, guess they came through.

This still doesn't explain why the Jeep dealer would tell me they set 'em to "10%" (maybe they meant using a ratio of .900, or 10% drop from 'input voltage'?).

Unless they're attempting to compensate for the altitude? (~ 5000 ft.) Which suggests that to really set it "spot on", would require taking a mixture reading of some sort (open loop, at WOT, or ??). But again, not really having a test tool that would do that (or a wideband O2 setup, etc.), would mean my settings would be guesswork at best.

Anyone have any experience with altitude compensation on these XJs?

One hint for Alpine: priority one, get yourself a "high altitude" CPS sensor (crank position sensor); about 10 degrees advance from factory base setting -- I think I got mine from NAPA -- way improved running at 5,000 ft & above...

Again, having never seen the '89 factory procedure, I can only present this as "what I found" -- beyond that you're on your own...

(there is an '88 factory procedure out on the net -- but as noted, the "VIN H" 2.5L procedure does not seem to apply)

alpine.adrenaline

Nice research, bdf_tech! I definitely went with the high alt. CPS since I usually drive the Jeep at 9K ft, but I'm going to go out to my XJ right now and play with that procedure. Thanks man!