Adjusting TPS lessons

I have a 88 XJ and in the past year or so I replaced my TPS. I got out the instructions and set the feed back ratio to 83% like the book says. I took it into the dealer for a problem, the mechanic ran it on the test set and found a failed ERG. He also told me my TPS was out of adjustment and he put it back to spec for me.

I noticed the "at home" method has you use the transmisson connectior. The dealer method uses the engine connector since it is hooked up to the engine computer. The value at idle is 13% measuring on the engine connector.

I have heard on here that you need to use the Jeep/Eagle test set OR the snap-on MT2500. I have been looking at Ebay and finally bid on a used snap on unit. I had it deliver on Friday and over the weekend have been using it.

I used it on my 88 XJ and it only gives me current values, like everyone said, since the Renix has no memory. I then tried it on a buddies 88 oldsmobile with the buick 3800 V6. We did the TPS check and found he had a low value BUT no error code had set. He had installed a new TPS and used the multimeter method. So we adjusted his back into range.

I then took the unit to my cousin's and tried it on his 85 vette. We also did the TPS check and found he was out of range, he was also low. He had installed a new TPS using the multimeter method. We found this after our first drive - nothing like a 123 mph test drive We then set the TPS to the correct value using the snap-on tool then went for a second drive. He noticed it had more seat of the pants power but it solved his idle problem. He was sold just on getting a better idle.

We talked and concluded the multimeter method does NOT take in account any voltage drop in the vehicle harness. Using the test set you can find out what value the engine computer is using.

My thoughts are us renix XJ owners need to use the test set to calibrate the TPS, the multimeter is better than nothing but it appears the snap on tool is the way to go.

I did look a while and concluded I better buy a snap on scanner that said it had a "GM-FORD-CHRYSLER-JEEP" catridge. Some of the scanners had 93 cartridge but it only listed GM-FORD-Chrysler" so I was not sure. Also if you look on ebay make sure it has the Jeep-1 connector included for your renix XJ.

You didnt mention how it affected your '88?Did you get a smoother idle,more throttle response also?My idle has always bugged me,very low and kinda bumpy.I too have adjusted TPS with multi meter,unfortunately I dont know how smooth you can actually get an xj since the TPS among other things were not working when I bought my '90.Egr should probably be suspect also?

Which arm did you give for that tool? so they do make a reader for older xj's.Is it a "real time" type reader?

MACH90XJ,

I am unsure of the change in my XJs operation when the dealer adjusted the TPS, that same trip it was into him because it ran bad and he installed a new EGR.

I am sure we all noticed it is to the point you need some type of scanner to work on vehicles. It would of been nice if we Renix guys would buy one of the $50 to $150 scanners but not our luck.

I just happened to find a good deal on Ebay and went for it. I see other ones on ebay with higher bids and less stuff or older data cartrages. Just watch and in time you will fine the bargin.

I also have vehicle beside the XJ and figured this was my time to jump in with both feet. My dealer will charge me $70 to "diagnose" the XJ. I figure I can off set the price of the tool by the trips I save into the service dept; also, IF something is acting up I can hook up the tool and figure out today while it is doing it instead of waiting till tomorrow. I will pay for the tool in less than 10 hours of diagnostic time. Remember I have also set the TPS on two GM products so that an added capability. I may check my sisters Explorer when I go see her this next week.

I was also affraid the dealers renix test set may fail one day and I'd be stuck. I'll tell you a funny one, 2 years ago I purchased the cruise control tester for my XJ, last one Mueller speical tool had, and the dealer mechanic used it to fix my XJ. They said "the tool no longer available and we don't have one". In the past 2 weeks I had the same dealer mechanic call me and ask for my cruise control tester. So with the Renix XJ, if you plan on keeping it having your own speical tools is just self preservation.

why not just check it on the other end of the harness?

Martin. What's the part number on that SNap On? I'd like to keep an eye out for it.

It doesn't do OBD II as well does it? (that'd ba asking a lot! The girlfirend's Neon is that...but I'm more concerned with my Renix)

Thanks,
Sequoia

Sequoia,

If you are to by it new it is a very expensive tool. It is the MT2500 series scanner. Here is the snap on page for it. Examine it and over time you will understand how they provide updates, etc:

Link: http://buy1.snapon.com/catalog/pro_...&group_ID=3098&store=snapon-store&dir=catalog

For a "new" one this tool costs $2400 tool accoring to the web site. Here what is says it can do:

1980-1/2 and later GM coverage including Saturn (Engine, Transmission, Airbag, and ABS).
1981 and later Ford Coverage (Engine, Transmission, Airbag, Body, and ABS).
1983 and later Chrysler Coverage (Engine, Body, Transmission, and ABS).
1984 and later Jeep Coverage (Engine, Transmission, Body and ABS).
Fast-Track troubleshooter tips for Transmission and ABS covering Domestic and Asian Imports require optional software.
Optional Asian Import coverage is also available for the 15 most popular makes.
Generic OBD-ll coverage for most Domestic, Asian Import and European through current model year.

When you look on ebay you will find older models that lock the coverage. It looks like you can buy from snap on any component you are missing or if you want to upgrade.

Yes, it does OBD II but the current data offered is through 2001.

HTH, good hunting!

Martin

I am a new member of this site. I have a 87 XJ and have put a new TPS on, I "eyeballed" the placement of the old unit. I don't have the preformance that should be there, no overdrive when on the road, but when you slow down at a coast it changes to OD.
My question is what is the procedure to adjust the TPS, from bolting it on the throttle body,no wires hooked yet.
AS if you are replacing it?

Thank you all for the great site for the XJ's.
WVridgerunner