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Thread: 97 XJ Cherokee

  1. #1
    Advanced Tuner axekick's Avatar
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    97 XJ Cherokee

    I thought about hijacking the 99 XJ thread but I didn't want to be rude and I suspect the 99 and 97 XJs are a little different.

    I got my MVPI2. I hooked it up last night, pulled the tune without any problems and made a short data log with it running. Here are a couple of things I noticed... My Fuel Trims seem stuck. Even on my way to work the LTFT and STFT were the same all the way to work. They were something like -3 for STFT and 1.5 for LTFT. If they aren't moving, I'll have to do any fuel tuning with my wideband or based on the narrowband voltage but I'd rather get it trimming like it should. It was commanding Closed Loop, BTW.



    Also, There was no PID for MAP that was working. There's a "Manifold vacuum" PID but it stayed at 60kpa even though the MAP Voltage seemed to be reading correctly. I'll have to make a custom PID to log MAP based on voltage. I can't understand the numbers in the tune for the MAP sensor curve. Maybe someone can help with that.



    Lastly, my engine coolant temperature was stuck at 90 degrees F the whole time. I suspect my sensor is bad. I unplugged it to see if it would change and it did. It went to -40 deg and threw a CEL. Then when I plugged it back in it stayed stuck at -40. I'll try to get a sensor today and see if that fixes that.



    I haven't started making changes in the tune yet. I need to be able to monitor some of these parameters before I'll feel comfortable making changes.
    I'll post my log file later today.
    2006 Tahoe
    Iron ls2, built up 4l60e w/vig 3000 stall, 232/234 114, 4.30s, LTs, ORY NNBS intake and LS2 TB etc.

    Fighting solves everything...
    ...except partial differential equations.


    Click here to combine multiple VE Logs into one.


  2. #2
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    Not much difference between the 97 and 99. About the only real difference is the intake manifold design. Other than that, I'm pretty sure damn near everything will interchange.

    In 2000, the big change with the XJ (and 4.0's in general) is the change form a single ignition coil\distributor\rotor\cap to a Coil-On-Plug (COP) setup.

    4.0 XJ's (and maybe the WJ's?) used the Asin-Warner 4 speed automatic trans with a separate TCM from 87-01.

    The 4.0 Wranglers and Grand Cherokees used the Chrysler 32RH, 42RH, and 42RE transmissions. The 42RE was an electronic shift trans and used in 97+ Wranglers and Grand Cherokees but I believe the transmission control was incorporated in the ECM.

    4.0 XJ's in some ways are very different animals from the Wrangler and Grand Cherokee.
    Last edited by grimmechanic; 10-15-2019 at 10:48 PM.

  3. #3
    Advanced Tuner axekick's Avatar
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    Ah, good info. I assumed yours was a COP jeep. So can you scan for MAP in kpa? Also, mine is a manual so I don't have to worry about shift tuning. I wish it was an auto but you get what you get sometimes. I'm excited to get to tune mine. Once I get everything working right, I'll get into the Jeep tuning business. I've been tuning LS cars and trucks for nearly 10 years.
    2006 Tahoe
    Iron ls2, built up 4l60e w/vig 3000 stall, 232/234 114, 4.30s, LTs, ORY NNBS intake and LS2 TB etc.

    Fighting solves everything...
    ...except partial differential equations.


    Click here to combine multiple VE Logs into one.


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    Quote Originally Posted by axekick View Post
    I thought about hijacking the 99 XJ thread but I didn't want to be rude and I suspect the 99 and 97 XJs are a little different.

    I got my MVPI2. I hooked it up last night, pulled the tune without any problems and made a short data log with it running. Here are a couple of things I noticed... My Fuel Trims seem stuck. Even on my way to work the LTFT and STFT were the same all the way to work. They were something like -3 for STFT and 1.5 for LTFT. If they aren't moving, I'll have to do any fuel tuning with my wideband or based on the narrowband voltage but I'd rather get it trimming like it should. It was commanding Closed Loop, BTW.



    Also, There was no PID for MAP that was working. There's a "Manifold vacuum" PID but it stayed at 60kpa even though the MAP Voltage seemed to be reading correctly. I'll have to make a custom PID to log MAP based on voltage. I can't understand the numbers in the tune for the MAP sensor curve. Maybe someone can help with that.



    Lastly, my engine coolant temperature was stuck at 90 degrees F the whole time. I suspect my sensor is bad. I unplugged it to see if it would change and it did. It went to -40 deg and threw a CEL. Then when I plugged it back in it stayed stuck at -40. I'll try to get a sensor today and see if that fixes that.



    I haven't started making changes in the tune yet. I need to be able to monitor some of these parameters before I'll feel comfortable making changes.
    I'll post my log file later today.
    So, LT and ST trims don't seem vary much on these. I've noticed this over time with my Matco scanner. The issue with your temp and baro may not be with your sensors. If the engine is running fine and not throwing a code for the MAP (barometric sensor), it's probably working fine. This ECM is heavily dependent on the MAP and if its not working, it's going to run like ass. Same for your coolant sensor. The same sensor is used for the dash gage and if the dash gage is working, then the sensor is likely good.

    I'm thinking you are seeing the same problem I've seen with communication issues with the HPT scanner.

    The main fuel table 'FUEL BASE -EGR OFF' is the one you want to use for fuel changes. The numbers in the fields are injector pulse time in microseconds. Fuel is based on manifold air pressure and RPM with some modifiers for cold start, etc. Of course, this is that base map. The 'FUEL BASE -EGR ON' is of no use since 97+ 4.0's do not have an EGR valve, and its disabled in the OE tune.

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    Quote Originally Posted by axekick View Post
    Ah, good info. I assumed yours was a COP jeep. So can you scan for MAP in kpa? Also, mine is a manual so I don't have to worry about shift tuning. I wish it was an auto but you get what you get sometimes. I'm excited to get to tune mine. Once I get everything working right, I'll get into the Jeep tuning business. I've been tuning LS cars and trucks for nearly 10 years.
    I believe you can convert the units in the editor. The native units (in my Matco scanner) are PSI for the MAP sensor and that's what shows up on the HPT scanner. But in the editor, MAP is displayed as KPa. No big deal, KPa can be converted easily to PSIA. 100 KPa is atmospheric pressure, about 14.7 PSIA, and 50 KPa would be half that, about 7.35 PSIA.

    At my altitude (4,500 feet), cruise is around 7 PSI on the MAP (48 KPa), light acceleration is 9.5 to 11 PSI (65.5 to 75.8 KPa), and idle is 4.8 PSI (33 KPa).

  6. #6
    Advanced Tuner axekick's Avatar
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    No, my problem isn't a unit conversion. It looks like the only options I have are manifold vacuum and MAP sensor voltage. My manifold vacuum reads 60 kpa all the time. The map sensor voltage seems to work as expected but I have to figure out the math that the PCM uses to convert voltage to vacuum.

    Maybe I should try the non-beta version.
    2006 Tahoe
    Iron ls2, built up 4l60e w/vig 3000 stall, 232/234 114, 4.30s, LTs, ORY NNBS intake and LS2 TB etc.

    Fighting solves everything...
    ...except partial differential equations.


    Click here to combine multiple VE Logs into one.


  7. #7
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    Quote Originally Posted by axekick View Post
    No, my problem isn't a unit conversion. It looks like the only options I have are manifold vacuum and MAP sensor voltage. My manifold vacuum reads 60 kpa all the time. The map sensor voltage seems to work as expected but I have to figure out the math that the PCM uses to convert voltage to vacuum.

    Maybe I should try the non-beta version.
    Non-beta version wont work right now on the 4.0's. Try reinstalling the beta version and make sure all of your drivers and firmware are updated.

  8. #8
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    Performance wise, on the stock 4.0 engine, there isn't going to be much gain with a re-tune. Maybe a little better fuel economy by forcing open-loop and leaning out the cruise fuel. Another improvement may be richening up the idle a tad to get smoother off-idle performance and idle quality. These things really run lean at idle. With a CO meter ahead of the cat, the CO is under 1%. Getting the CO above 2% will help idle quality. O2 can be a little deceptive for tuning idle quality because depending on the camshaft profile, there can be air introduced into the exhaust during overlap the leads an O2 sensor to show a false lean condition. CO under some conditions is a better indicator of mixture than O2.

    This 4.0 calibration also seems to be really tame on the ignition advance as well. Maybe some gains there.

    In my experience with the stock 99 and older 4.0 engine, the biggest single improvement in performance was by by replacing the exhaust from the cylinder head to the cat. The stock 4.0 front exhaust from 87-99 is horrible. There isn't anything on the market to address this problem. The stock exhaust manifold chokes down to 1-5/8" inches where it connects to the down pipe and it's under 2" all the way to the cat. I got tired of replacing the stock crappy welded-tube exhaust manifold because of the cracking problem they all have. What I ended up doing was to replace the 87-99 single outlet manifold with the 2000+ 2-piece, dual outlet, cast-iron manifold. Problem is, the 2000+ exhaust manifolds wont fit the 99 and older heads without some modification. I had to weld the flange on the bottom sides of the exhaust ports and enlarge the openings to match the earlier head. Using the 2000+ dual outlet manifolds, and the non-California (no pre cats) 2000-2001 XJ down pipe, I got a full 2-1/2" back to the cat. And I added a full 2-1/2" exhaust with a Flowmaster muffler to the rear bumper. This change made a HUGE difference in power. I wished I had before and after dyno runs, but the seat of the pants feeling was that I gained 20-30 HP easily. I also picked up about 2 mpg by fixing the choked up front exhaust. I get a consistent 20+ mpg in mixed driving.
    Last edited by grimmechanic; 10-15-2019 at 11:29 AM.

  9. #9
    Advanced Tuner axekick's Avatar
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    That sounds like a great mod. I'll get to play with my scanner again some at lunch. I'm going to go get a temp sensor and if I can't get some of my PIDs to work like they should I'll submit it to HPT Support. I'm happy to have this dialogue going. I don't expect to be able to make huge gains through tuning, but I'll be ready to tune for mods that do make nice gains.
    2006 Tahoe
    Iron ls2, built up 4l60e w/vig 3000 stall, 232/234 114, 4.30s, LTs, ORY NNBS intake and LS2 TB etc.

    Fighting solves everything...
    ...except partial differential equations.


    Click here to combine multiple VE Logs into one.


  10. #10
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    Quote Originally Posted by axekick View Post
    No, my problem isn't a unit conversion. It looks like the only options I have are manifold vacuum and MAP sensor voltage. My manifold vacuum reads 60 kpa all the time. The map sensor voltage seems to work as expected but I have to figure out the math that the PCM uses to convert voltage to vacuum.

    Maybe I should try the non-beta version.
    Again try reinstalling the Beta or returning all of your display settings to the defaults. The default display should have the MAP chart but the units are not in PSI. My default display does not show the MAP volts but it does show the MAP KPa in chart group 2. I assume you are looking at the charts and not the histogram (graph).

    Manifold "vacuum" is going to be that same chart/group/series as MAP pressure output. It's a unit conversion thing. I don't see a "manifold vacuum" listed in any of the channels. I tried searching the channels and didn't see anything with "vacuum". The data for the MAP comes from the "intake manifold absolute pressure" channel. You can change units in this channel from KPa to PSI, or inches Hg.

    So, if you want to change the units in your chart, right click over the chart you want to change, click on "charts layout". You'll see a list of 'groups' and under each 'group' will be a list of 'series'. Each 'group' corresponds to a chart. When you open up the scanner for the XJ tune and everything is at the default settings, the default group that has MAP should be displayed under "Group 2/MAP". The default units for this group/series is in KPa. Left click on "MAP" and change the units to PSI.

    If you have a MAP series that is showing in V, it was something that you added. It works with my 99 and there was no 'MAP volts' in the default group/series.

    I don't know if this is a subtle difference between the OS between the two years, but it would be surprising since there is little other changes between these two vehicles. The manual trans shouldn't make a difference.
    Last edited by grimmechanic; 10-16-2019 at 09:35 PM.

  11. #11
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    I got to play around again at lunch. I reinstalled the Beta and that got my MAP reading correctly so that's great! I also went and bought a new temperature sensor but that did not fix my coolant temp problem. It still reads -40 on my scanner even though the gauge on my dash works just like it should and the engine is running perfectly fine. I had to reset the CEL by unplugging the battery but it didn't come back on. Another thing I noticed with the latest scanner, my Fuel trims look weird in the channels list, like -100 for all of them except STFT Bank 2 which I don't even think matters. That one says -23. However, in the graph it looks more normal. STFT are -.62 and LTFT are -1 across the board. I'm sure this info doesn't help anyone but I'm just keeping track of where I'm at. I'm going to submit an info log and scan to Support but I'll post them here too in case anyone cares.
    Attached Files Attached Files
    2006 Tahoe
    Iron ls2, built up 4l60e w/vig 3000 stall, 232/234 114, 4.30s, LTs, ORY NNBS intake and LS2 TB etc.

    Fighting solves everything...
    ...except partial differential equations.


    Click here to combine multiple VE Logs into one.


  12. #12
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    Quote Originally Posted by axekick View Post
    I got to play around again at lunch. I reinstalled the Beta and that got my MAP reading correctly so that's great! I also went and bought a new temperature sensor but that did not fix my coolant temp problem. It still reads -40 on my scanner even though the gauge on my dash works just like it should and the engine is running perfectly fine. I had to reset the CEL by unplugging the battery but it didn't come back on. Another thing I noticed with the latest scanner, my Fuel trims look weird in the channels list, like -100 for all of them except STFT Bank 2 which I don't even think matters. That one says -23. However, in the graph it looks more normal. STFT are -.62 and LTFT are -1 across the board. I'm sure this info doesn't help anyone but I'm just keeping track of where I'm at. I'm going to submit an info log and scan to Support but I'll post them here too in case anyone cares.
    Thta's excellent! I made a few more changes to mine and did some testing. I'll post what's been done on the 99 XJ thread.

  13. #13
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    So I'm able to flash changes and support was great getting my scanner issues dealt with on the latest beta. However, my trims, or "fuel multiplier" numbers are very high and adding to my base fuel maps doesn't seem to help so I'll have to do some experiments to see how they all play together.
    Last edited by axekick; 10-21-2019 at 10:33 AM.

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    After playing with the base fueling table over the weekend, I've come to the conclusion that Long Term and Short Term Fuel Multipliers are not the same as fuel trims. Mine are as high as 60 for much of the map, that's long term and short term but adding or subtracting from my fuel table doesn't bring them closer to zero in any predictable fashion. I haven't been able to get any negative numbers. I'll keep bugging support about it. They do seem interested in helping so that's awesome.
    2006 Tahoe
    Iron ls2, built up 4l60e w/vig 3000 stall, 232/234 114, 4.30s, LTs, ORY NNBS intake and LS2 TB etc.

    Fighting solves everything...
    ...except partial differential equations.


    Click here to combine multiple VE Logs into one.


  15. #15
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    Beta 4.5.853 solved all of the scanner issues I was having for my Jeep. I can finally see MAP, ETC and Trims all working properly. That is exciting to me! But beware, mine now takes a full 45 minutes to flash. I've tried it twice and it took that long both times. I have been in contact with support and they've been great at working on these issues so I expect this to be a temporary problem.
    2006 Tahoe
    Iron ls2, built up 4l60e w/vig 3000 stall, 232/234 114, 4.30s, LTs, ORY NNBS intake and LS2 TB etc.

    Fighting solves everything...
    ...except partial differential equations.


    Click here to combine multiple VE Logs into one.


  16. #16
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    Support has been really great through this process. My scanner works now for everything I need to see and the editor now writes normally. Now I just need to learn how to deal with baro calculations with a 2 bar map and I?m ready to start building and tuning some turbo Jeeps and dodges!