88mjgilley Posted February 23, 2013 Share Posted February 23, 2013 ok so my 88 mj does some wierd stuff some times it runs 100% and other times well it doesnt when it is acting up if you give it much throttle it cuts out and will either loose everything or back fires threw the intake or numerous other thing i have been beating my head at it for a while and really can't seem to track it down and also it only does it once its a operating temp when its cold it runs perfect and some days it doesnt have a single issue tonight i couldnt even get it over 35 and most times if i shut it off and let it sit for a minute or two it will come out of it for a few minutes also my tach doesnt drop off when its doing it so i really don't think its the cps it has confused the hell out of me Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 23, 2013 Share Posted February 23, 2013 Jezus, not one period. reading thru yur post it's hard to figur out what ur saying bt if i read correctly it sounds lik yr not switching fm closed to open loop maybe try a new O2 sensor or check wiring for fries. Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted February 23, 2013 Share Posted February 23, 2013 Sounds like you and I are having the same problem... I have a thread started and am currently awaiting some more replies if you'd like to follow it. I'm sure that it will benefit you as well. What engine do you have, by the way and is yours an automatic or stick? That thread I was talking about.... http://comancheclub.com/topic/37396-25l-tbi-help/ Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 wouldnt the o2 cause crappy fuel milage tho? Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 4.0 5spd currently bone stock for a few more days or untill i get this crap figured out Link to comment Share on other sites More sharing options...
JeepcoMJ Posted February 23, 2013 Share Posted February 23, 2013 sounds like the CPS wire is laying on the exhaust manifold. I've had similar experiences with that exact issue. Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 i have been thinkin possiably ingintion control mod. i am planing on getting that a coil, another tps, cam pick up, and a air intake sensor tomorrow hopeing one of them will fix it and i really don't think cps seems how my rps never drop well they drop but the tach doesnt bounce around when its doing its stupid stuff Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 but i guess ill go buy a new cps and o2 sensor also this ting is wearing on me needless to say Link to comment Share on other sites More sharing options...
cruiser54 Posted February 23, 2013 Share Posted February 23, 2013 i have been thinkin possiably ingintion control mod. i am planing on getting that a coil, another tps, cam pick up, and a air intake sensor tomorrow hopeing one of them will fix it and i really don't think cps seems how my rps never drop well they drop but the tach doesnt bounce around when its doing its stupid stuff Don't "shotgun" it with parts for crying out loud. Backfire through intake is typically lack of fuel. YOu could have an intermittent/weak fuel pump. Before replacing the coil/ICU, do this simple refreshing. Renix Jeep ICU/Coil contact refreshing The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future. The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner. Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU. While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in. I feel this procedure should be performed at least once in the lifetime of a Renix Jeep. Revised 11-29-2011 Since it's an 88, do this: Renix Jeep C101 Connector Refreshing The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before. Almost every critical signal between the engine sensors, injectors, ECU, and some to the TCU, travel this path through the C101 connector. The C101 connector is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time. Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth. If you have a small pick or dental tool, tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter before bolting both halves back together. Revised 07-17-2012 And eVERY Renix era Jeep needs this done: 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, and wasted money replacing unnecessary components. 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 12-04-2012 Link to comment Share on other sites More sharing options...
Dirteatr717 Posted February 23, 2013 Share Posted February 23, 2013 Spam alert! Link to comment Share on other sites More sharing options...
Eagle Posted February 23, 2013 Share Posted February 23, 2013 Jezus, not one period. reading thru yur post it's hard to figur out what ur saying bt if i read correctly it sounds lik yr not switching fm closed to open loop maybe try a new O2 sensor or check wiring for fries. An alternate diagnosis would be that it IS switching from open loop (warm-up) mode to closed loop mode, and that one or more of the sensors used in closed-loop mode is faulty. Several sensors are by-passed in open-loop mode, so if it runs fine with sensors by-passed then doesn't run well with the sensors are in the loop ... that should tell you where to start looking. I think the oxygen sensor would be a good place to start. Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 Also brand new fuel pump installed last night. I have by passed the balast resistor, and also when it does its stuff the fuel pump is screaming untill it starts then it goes quiet. The old pump did this also thats why i bought a new one. Any one know a common spot for the fuel pump wireing to be bad, or do you still thing it would be open/ closed loop? Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 Also i have cleaned all my grounds, plugs and the c101 connector Link to comment Share on other sites More sharing options...
cruiser54 Posted February 23, 2013 Share Posted February 23, 2013 also brand new fuel pump installed last night i have by passed the balast resistor and also when it does its stuff the fuel pump is screaming untill it starts then it goes quiet the old pump did this also thats why i bought a new one. any one know a common spot for the fuel pump wireing to be bad or do you still thing it would be open/ closed loop? Your lack of punctuation gives me, and those other old guys who can help you, a frickin headache. When you replaced the pump, did you replace the hoses in the tank that run to/from the pump? Link to comment Share on other sites More sharing options...
cruiser54 Posted February 23, 2013 Share Posted February 23, 2013 Spam alert! Must have glommed on to the thread title: head pounder!! LOL. Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 yes i replaced the hoses Link to comment Share on other sites More sharing options...
cruiser54 Posted February 23, 2013 Share Posted February 23, 2013 Ever refresh the ground behind the driver's side taillamp? It's for the fuel pump among other things. Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 yes i have followed allmost all of your Renix tips. I did them all with in the first week of buying it Link to comment Share on other sites More sharing options...
onlyinajeep726 Posted February 23, 2013 Share Posted February 23, 2013 Ever refresh the ground behind the driver's side taillamp? It's for the fuel pump among other things. I will be checking this on mine too since you mentioned it. :idea: Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 23, 2013 Share Posted February 23, 2013 An alternate diagnosis would be that it IS switching from open loop (warm-up) mode to closed loop mode, and that one or more of the sensors used in closed-loop mode is faulty. Several sensors are by-passed in open-loop mode, so if it runs fine with sensors by-passed then doesn't run well with the sensors are in the loop ... that should tell you where to start looking. I think the oxygen sensor would be a good place to start. Yep, that's what I meant, open to closed loop. Had them reversed. :doh: (Head Pounder) Change the O2 mate. Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 any way to by pass it? possibly un plug it? Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 23, 2013 Share Posted February 23, 2013 any way to by pass it? possibly un plug it? Without the O2 sensor, you will stay in open loop meaning your computer will automatically default to a very rich mixture. You will get terrible gas mileage, less power, and fouled spark plugs at a minimum. Not recommended. Link to comment Share on other sites More sharing options...
88mjgilley Posted February 23, 2013 Author Share Posted February 23, 2013 ok so far in the past 24hrs i have replaced cps, air intake temp, ingintion control module, fuel pressure regulator, map sensor, coil, fuel pump, fuel pressure regulator. I have also bypassed the factory wiring on the fuel pump so i could turn a switch on to send power directly to it when it started acting up, and that didnt help at all. New o2 sensor will be here tomorrow afternoon Link to comment Share on other sites More sharing options...
cruiser54 Posted February 23, 2013 Share Posted February 23, 2013 Shotgun those parts at it!!! Link to comment Share on other sites More sharing options...
ComancheKid45 Posted February 23, 2013 Share Posted February 23, 2013 Just outta curiosity, check the wiring above the parking brake assembly for rub marks or possibly breaks... Link to comment Share on other sites More sharing options...
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