JeepComanche89 Posted March 5, 2013 Share Posted March 5, 2013 So I have a 89 4.0, ax-15 combo, with 32,000 on the clock. I have been having some idle surging problem, and intermittent starting issues. I replaced the iac, tps, and eventually ended up replacing the icm. Everything seemed good after that, until now. When starting it when cold, it ha been idling very low, around the 500 range (needle is just above the zero mark on the tach). The truck is starting fine, but sometimes it wants to die when idling because it is so low. Once running for a couple minutes, it straightens right out, and is up around 700. My question is what could be causing this? I adjusted the new TPS, per cruisers tips, but is there I way I can further adjust it to correct this, or is it unrelated? Any help would be appreciated, TIA. Link to comment Share on other sites More sharing options...
jeepcoma Posted March 5, 2013 Share Posted March 5, 2013 I'm having a similar problem on my '91 HO. It seems to be worse when the outside air temp is colder. My guess is it's the coolant temp sensor, though I haven't gotten around to testing it yet. Link to comment Share on other sites More sharing options...
Biotex Posted March 5, 2013 Share Posted March 5, 2013 I'm still trying to wrap my head around the emissions and FI portion on these engines, but I believe a leaking EGR will cause a drop in idle. Might be only happening when it is cold. Link to comment Share on other sites More sharing options...
1987Comanche Posted March 5, 2013 Share Posted March 5, 2013 There's a documented TSB on cold idle/driveway die out when cold. The factory ECU mapping is not correct for all temps. The fix is a MOPAR reflashed ECU with the correct tables. I don't remember the P/N offhand but there's a M/T and A/T version. I can verify the remapped ECU solves this issue...found that particular piece of unobtainum and ran it in my '90 for 2+ years. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 5, 2013 Author Share Posted March 5, 2013 I'm still trying to wrap my head around the emissions and FI portion on these engines, but I believe a leaking EGR will cause a drop in idle. Might be only happening when it is cold. Interesting, I will take that into consideration. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 5, 2013 Author Share Posted March 5, 2013 There's a documented TSB on cold idle/driveway die out when cold. The factory ECU mapping is not correct for all temps. The fix is a MOPAR reflashed ECU with the correct tables. I don't remember the P/N offhand but there's a M/T and A/T version. I can verify the remapped ECU solves this issue...found that particular piece of unobtainum and ran it in my '90 for 2+ years. Never heard of that, I will look into it though. Sorry but whats TSB? I have a MT but the engine was from an auto, do you think that could be part of the issue? Link to comment Share on other sites More sharing options...
1987Comanche Posted March 5, 2013 Share Posted March 5, 2013 TSB=technical service bulletin. I looked it up from my archives: TSB # 18-54-89 Revision A M/T ECU: 53007842 A/T ECU: 53007843 These P/Ns were superceeded by a later number. The M/T ECU that I have is the superceded # (look for a MOPAR Reman tag on the ECU...has the P/N). As long as everything was hooked up correctly the fact that the engine came from an auto shouldn't matter. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 5, 2013 Share Posted March 5, 2013 So I have a 89 4.0, ax-15 combo, with 32,000 on the clock. I have been having some idle surging problem, and intermittent starting issues. I replaced the iac, tps, and eventually ended up replacing the icm. Everything seemed good after that, until now. When starting it when cold, it ha been idling very low, around the 500 range (needle is just above the zero mark on the tach). The truck is starting fine, but sometimes it wants to die when idling because it is so low. Once running for a couple minutes, it straightens right out, and is up around 700. My question is what could be causing this? I adjusted the new TPS, per cruisers tips, but is there I way I can further adjust it to correct this, or is it unrelated? Any help would be appreciated, TIA. Have you cleaned your throttle body? Did you do the sensor ground test included in the TPS instructions? Have you ever checked your intake manifold bolts for looseness? Link to comment Share on other sites More sharing options...
Biotex Posted March 5, 2013 Share Posted March 5, 2013 Cruiser, please educate me on the effect of a vacuum leak on our renix systems. On carburated engines a vacuum leak raises the idle. I'm not able to test it out, but what happens if the intake leaks? Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 5, 2013 Author Share Posted March 5, 2013 TSB=technical service bulletin. I looked it up from my archives: TSB # 18-54-89 Revision A M/T ECU: 53007842 A/T ECU: 53007843 These P/Ns were superceeded by a later number. The M/T ECU that I have is the superceded # (look for a MOPAR Reman tag on the ECU...has the P/N). As long as everything was hooked up correctly the fact that the engine came from an auto shouldn't matter. ok thanks, I will look into it, but I'm kinda leaning towards the egr, because it does correct itself once warm. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 5, 2013 Author Share Posted March 5, 2013 Have you cleaned your throttle body? Did you do the sensor ground test included in the TPS instructions? Have you ever checked your intake manifold bolts for looseness? Yeah, I cleaned the throttle body spotless before re installing it. And the tps ground showed no resistance when wiggling the wires as said in your instructions. And manifold bolts are defiantly tight Link to comment Share on other sites More sharing options...
cruiser54 Posted March 5, 2013 Share Posted March 5, 2013 Cruiser, please educate me on the effect of a vacuum leak on our renix systems. On carburated engines a vacuum leak raises the idle. I'm not able to test it out, but what happens if the intake leaks? Unmetered air enters the system. O2 sensor thinks it's lean mixture, increase the pulse width of the injectors to richen the mixture. Low manifold vacuum read by the MAP sensor tells the eCU the engine is under a load and it needs more fuel, so The ECU adds it. Have you done the complete ground refreshing per my instructions? Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 6, 2013 Author Share Posted March 6, 2013 No, I have not upgraded any grounds yet. But all of the grounds I have come across I cleaned the very well, and then reattached with dielectric grease as a preventative measure. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 6, 2013 Share Posted March 6, 2013 No, I have not upgraded any grounds yet. But all of the grounds I have come across I cleaned the very well, and then reattached with dielectric grease as a preventative measure. Renix Ground Refreshing The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily. The components grounding at the dipstick tube stud are: Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff. The factory was aware of the issues with this ground point and addressed it by suggesting the following: Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint. Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely. While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely. Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end. First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely. Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely. A suggestion regarding the braided cable: I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116. A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115. For those of us with Comanches, it’s very important to remove the driver’s side taillamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Reattach securely. If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price. Revised 03-04-2013 Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 6, 2013 Author Share Posted March 6, 2013 Thanks for the link but 200 bucks is just too much for me to spend. What ground would you susspect to be the culprit? I plan on upgrading them all eventually, but anywhere in particular to start? Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 6, 2013 Author Share Posted March 6, 2013 Where is the vaccum line that comes from the egr tube connect to? The round black plastic thing? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 6, 2013 Share Posted March 6, 2013 Thanks for the link but 200 bucks is just too much for me to spend. What ground would you susspect to be the culprit? I plan on upgrading them all eventually, but anywhere in particular to start? Do the whole refreshing cutting no corners. Just skip the added cables to save money. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 6, 2013 Author Share Posted March 6, 2013 Do the whole refreshing cutting no corners. Just skip the added cables to save money. OK, I just re read that list and I have brand new quality battery cables. So the only ones I would be buying is the block to firewall, and alt output to distrib? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 6, 2013 Share Posted March 6, 2013 OK, I just re read that list and I have brand new quality battery cables. So the only ones I would be buying is the block to firewall, and alt output to distrib? NO! Just refresh the grounds. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 7, 2013 Author Share Posted March 7, 2013 NO! Just refresh the grounds. I'm confused now, i though you were suggesting buying the kit? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 7, 2013 Share Posted March 7, 2013 I'm confused now, i though you were suggesting buying the kit? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 7, 2013 Share Posted March 7, 2013 At a MINIMUM do the refreshing. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 8, 2013 Author Share Posted March 8, 2013 At a MINIMUM do the refreshing. OK, I already cleaned and reassembled if thats what you mean by refreshing Link to comment Share on other sites More sharing options...
cruiser54 Posted March 8, 2013 Share Posted March 8, 2013 OK, I already cleaned and reassembled if thats what you mean by refreshing All of them? Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 9, 2013 Author Share Posted March 9, 2013 All of them? To my knowledge, I did the ones on the dipstick, the head to firewall, the one for the fuel pump behind the tailight, underneath the steering column, another small one to the dash that under the column, and thats all I can think of right now. Link to comment Share on other sites More sharing options...
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