Akula69 Posted September 21, 2011 Share Posted September 21, 2011 Looking for advice on a RPM fluctuation that has started occuring in the 89. Here's the data: Under steady throttle (never happens under acceleration or deceleration) the RPM's will briefly drop by about 200 and then immediately rise back to where they had been. There is no set speed at which this happens - it can happen at any speed. there ar no other symptoms. My son describes it as feeling like a sudden gust of wind hits the front of the jeep while you are driving it. We have replaced the trans computer with a known working one without any effect. All the sensors (13) were replaced with an engine re-build in 08/10. The trans was flushed and the filter was replaced at that time. Any ideas are appreciated. Link to comment Share on other sites More sharing options...
Pete M Posted September 21, 2011 Share Posted September 21, 2011 tried cleaning out the throttle body yet? Link to comment Share on other sites More sharing options...
gl1200aman Posted September 21, 2011 Share Posted September 21, 2011 it is probably the TPS (throttle position sensor). I had a similar problem on my 90. I replaced the TPS and adjusted it per specs for an automatic and it continued to happen. I then adjusted it for a manual trans and it works good. Link to comment Share on other sites More sharing options...
deziped Posted September 21, 2011 Share Posted September 21, 2011 All else fails, check the OHMS of the 3 solenoids in the tranny. Check them by unplugging at TCU and probing transmission side of harnes with circuit tester, check as follows: Place NEG lead in D7 (ground) and then: Key OFF Probe C 14 (TC clutch solenoid), C 15 (Shift solenoid #2 (3rd gear), and while doing this you might as well check C16 (1st -2nd gear solenoid), however I don't think this one would cause symptons your describing. OHM range on all three should be 11 - 15 . One of these could be faulty causing it to move gear selection up or down . May be a speed sensor problem also. Good luck tracking problem Link to comment Share on other sites More sharing options...
Akula69 Posted September 21, 2011 Author Share Posted September 21, 2011 tried cleaning out the throttle body yet? We did that when the engine was gone through, but I will be re-cleaning it when I change out the TPS and clean the IAC. Link to comment Share on other sites More sharing options...
88 Beast Posted September 21, 2011 Share Posted September 21, 2011 All else fails, check the OHMS of the 3 solenoids in the tranny. Check them by unplugging at TCU and probing transmission side of harnes with circuit tester, check as follows: Place NEG lead in D7 (ground) and then: Key OFF Probe C 14 (TC clutch solenoid), C 15 (Shift solenoid #2 (3rd gear), and while doing this you might as well check C16 (1st -2nd gear solenoid), however I don't think this one would cause symptons your describing. OHM range on all three should be 11 - 15 . One of these could be faulty causing it to move gear selection up or down . May be a speed sensor problem also. Good luck tracking problem I think your on the right track with TC clutch as 200 RPM is about the difference between TC locked and unlocked. There is also a switch mounted above the brake switch that controls the signal to TCU to unlock convertor when brakes are applied. You can check the operation of the switch by cruising in OD and tapping brake pedal, RPM should rise about 200 RPM and then drop as convertor locks back up. Link to comment Share on other sites More sharing options...
HOrnbrod Posted September 22, 2011 Share Posted September 22, 2011 Jake, try adjusting the Throttle Valve cable (commonly called the kickdown cable) first. If maladjusted it will cause your AW4 shifting points to be all over the place. Takes no tools and about five minutes to do. 1: Push in and hold the release button 2: While holding in release button, push "conduit" in as far as it will go 3: Release button 4: Rotate throttle to WOT, some people do this with the gas pedal. Others do it from the engine compartment. 5: Hold at WOT for a few seconds, cable should ratchet out a click or two. 6: Your TV cable should now be properly adjusted. :cheers: Link to comment Share on other sites More sharing options...
Akula69 Posted September 22, 2011 Author Share Posted September 22, 2011 Don - Thanks for that suggestion - I never knew the shifting points were adjustable at that location! :cheers: Link to comment Share on other sites More sharing options...
deziped Posted September 22, 2011 Share Posted September 22, 2011 You can adjust the shift points by use of the accelerator also. Soft on the pedal equates to lower RPM shifts. Or stomp on it and it won't shift into 2nd until approximately 4500 RPM. Thats a jerk of an experience, if it doesn't bloo :oops: ooow first. Link to comment Share on other sites More sharing options...
Akula69 Posted October 13, 2011 Author Share Posted October 13, 2011 OK - here goes: We have adjusted the throttle cable; cleaned the throttle body and replaced the TPS and the IAC. Throttle response is MUCH better and shifting is crisper. However, the problem still exists. I will OHM out the solenoids this weekend. When dezipped sugests doing it at the TCU plug, doesn't he mean the two plugs in the engine bay? The TCU plug is on the main bay harness and only has one "side". Thanks Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 13, 2011 Share Posted October 13, 2011 He means unplugging the TCU under the right side lower dash and ohming out the solenoids at the connector pins. Link to comment Share on other sites More sharing options...
Akula69 Posted October 18, 2011 Author Share Posted October 18, 2011 Finally got the time to OHM out the TCU harness. The OHMS on each of the solenoids read in the 16.0 - 16.4 range with the key off. Only thing left is the speed sensor, and it is a seemingly high-priced item (lowest I've found is 76.00) the MOPAR number is 8350 3722 in case any of you enterprising folks wanna look for me ;) Rockauto only shows it for the AW4 on 93 and 94 XJ, but I crawled under the truck and noted it is there, plain as day... Does anyone have any info on testing this sensor? What the performance range (electroniclly) should be? Thanks Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 18, 2011 Share Posted October 18, 2011 I've been busy tracking down an AW4 problem too. Had a MAP and Cruise code fault and it was running about 300 RPM too high while cruising. No torque converter lockup I surmised. I tested the solenoids at the 7-pin grey plug at the back of the engine bay (easier than at the TCU connector), all were right at 15 ohms. Changed out the MAP, no help. The next step was to pull the speed sensor and bench test it like here: http://www.ehow.com/how_7683994_check-transmission-speed-sensors.html. But first I checked the brake switch. When the pedal is up (no braking), a closed contact completes the circuit to the TCU and allows TC lockup. When braking the switch opens unlocking the TC. My brake switch was not closing all the way to allow continuity to the TCU, so the TC wouldn't lock up. All it took was an adjustment and the TC locks up fine now. No more fault codes either. Sooo Jake-man, check your brake switch contacts before pulling the speed sensor. Link to comment Share on other sites More sharing options...
Akula69 Posted October 19, 2011 Author Share Posted October 19, 2011 Wouldn't ya know, we just replaced the brake switch about three weeks ago....hmmmm. Too dark out there now, but I will certainly check it out tomorrow. I wonder if the wiring could be the culprit...we have previously done the 93+ dual booster change-out, and I changed to the plunger-type brake switch (from the spade type). Because of the existing 89 harness connecting to the 93 brake switch only three wires from the switch are used (white/ light tan, white/light pink, pink/blue). I hope one of the other five are not for the TCU signal... :no: Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 19, 2011 Share Posted October 19, 2011 On the 91 the TC unlock wire from the brake switch is WHT/PNK. It comes from the NC contacts of the switch and terminates at TCU pin C10. WHT/TAN is the brake lamps, But in your case, :dunno: Link to comment Share on other sites More sharing options...
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