cjomanche Posted January 2, 2018 Share Posted January 2, 2018 Hi guys, still chasing a phantom gremlin in my rig. Hoping this video can help. Used to only do this intermittently at around 2900 rpms but now it does it all over once it gets up to temperature, and it gets progressively worse the longer the engine is run. Becomes undriveable after a while. Put in a new O2 sensor, tps, coil, spark plugs, fuel filter, distributor cap and rotor, did a fuel pressure check. Nothing has fixed this. No check engine light, but it has stored codes 12 and 35 (I think). Next step will be fuel injectors. Any other ideas? Link to comment Share on other sites More sharing options...
yxmj Posted January 2, 2018 Share Posted January 2, 2018 I just had something similar on a YJ Before you go too far try this Remove the negative (ground wire) battery cable..... One at a time pull the electrical plug off each injector..... Spray with electrical contact cleaner and Polish up with a q-tip or even a toothpick Replace all plugs and make sure they snap in...when done attach the battery ground and test run.....any difference? Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 2, 2018 Share Posted January 2, 2018 ^^ That's a good tactic and it's free. Along with that, pull the 60-pin ECU connector and check for any bent / recessed pins, then spray and clean both the male and female connectors with the same contact cleaner. Link to comment Share on other sites More sharing options...
cjomanche Posted January 3, 2018 Author Share Posted January 3, 2018 22 hours ago, yxmj said: I just had something similar on a YJ Before you go too far try this Remove the negative (ground wire) battery cable..... One at a time pull the electrical plug off each injector..... Spray with electrical contact cleaner and Polish up with a q-tip or even a toothpick Replace all plugs and make sure they snap in...when done attach the battery ground and test run.....any difference? We did try this and it didn't make a difference. Also tried putting in all new plug wires, we changed the CPS, disconnected the exhaust to see if the cat was at fault. Nothing has worked so far. We are really at a loss on what to try next. It seems electrical since the dash lights dim slightly whenever a misfire is occurring. I just don't know what could be doing this since the truck runs normally when cold. It's only after it starts warming up that this problem presents itself. Link to comment Share on other sites More sharing options...
DesertRat1991 Posted January 3, 2018 Share Posted January 3, 2018 What strikes me is the irregularity of the stumbling and the amount of RPMS you lose with each stumble. It's like you have an intermittent voltage dip. Considering everything else you've already replaced, I'd be looking at the ignition coil and ground connections next. Have you tried monitoring your alternator output while stumbling? Even though you don't have a Renix MJ, there is still a lot of useful guidance to be gleaned from Cruiser's tips for inspecting the ground connections, ICU, and relays: http://cruiser54.com/?p=19 http://cruiser54.com/?p=41 http://cruiser54.com/?p=35 Link to comment Share on other sites More sharing options...
cjomanche Posted January 4, 2018 Author Share Posted January 4, 2018 6 hours ago, DesertRat1991 said: What strikes me is the irregularity of the stumbling and the amount of RPMS you lose with each stumble. It's like you have an intermittent voltage dip. Considering everything else you've already replaced, I'd be looking at the ignition coil and ground connections next. Have you tried monitoring your alternator output while stumbling? Even though you don't have a Renix MJ, there is still a lot of useful guidance to be gleaned from Cruiser's tips for inspecting the ground connections, ICU, and relays: http://cruiser54.com/?p=19 http://cruiser54.com/?p=41 http://cruiser54.com/?p=35 We replaced the ignition coil and looked around at all the grounds. Visual inspection only but they looked ok. Will probably take a look at the alternator next Link to comment Share on other sites More sharing options...
rokinn Posted January 4, 2018 Share Posted January 4, 2018 I've seen engines behave this way from vacuum leaks. Might be worth looking at also. Link to comment Share on other sites More sharing options...
carnuck Posted January 4, 2018 Share Posted January 4, 2018 I've seen engines behave this way from vacuum leaks. Might be worth looking at also. Cracked vacuum can behind the passenger side bumper? It’s almost like one or two injectors stop spraying. The power drop makes me wonder about adding another negative from battery to body. That fixed my 2.5s starting and charging issues. Could a wire be sitting on the exhaust or pinched by a bolt on the block, like the O2 or CTS? Will it do that in park? If so, unplug the alternator (not the main terminal) and see if it goes away. Shorted diodes used to be a thing of the past, but they can really mess with electrics by throwing AC voltage across the diode which interferes with the computer and eventually kills the battery. Dirty battery terminals can do that too. Power spikes really mess with computers. My old Throttle Position Sensor affects my 2.5 too. I have to put the pedal in just the right position or it won’t start cold. I’ll fix it later but I have a 107,000 mile ‘90 4.0L AW4/NP231 and full harness to go in. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
Skorpyo Posted January 4, 2018 Share Posted January 4, 2018 15 hours ago, rokinn said: I've seen engines behave this way from vacuum leaks. Might be worth looking at also. Check that annoying one between the TB and the MAP sensor... always a nuisance to me... I'm planning on doing the nipple swap on @cruiser54s list... Link to comment Share on other sites More sharing options...
kryptronic Posted January 6, 2018 Share Posted January 6, 2018 If this is happening only after reaching operating temp, it's computer/sensor related. Had nearly an identical issue with a 2.5L HO YJ. Had to replace the entire distributor assembly to fix as the issue was the Camshaft Position Sensor. Other possibilites are a bad TPS, O2 Sensor or Crankshaft Position Sensor. IAC as well. But I bet its the Camshaft Position Sensor. Link to comment Share on other sites More sharing options...
HOrnbrod Posted January 6, 2018 Share Posted January 6, 2018 On 1/6/2018 at 8:14 AM, kryptronic said: If this is happening only after reaching operating temp, it's computer/sensor related. Had nearly an identical issue with a 2.5L HO YJ. Had to replace the entire distributor assembly to fix as the issue was the Camshaft Position Sensor. Other possibilites are a bad TPS, O2 Sensor or Crankshaft Position Sensor. IAC as well. But I bet its the Camshaft Position Sensor. I've had both the crank position sensor (twice) and the distributor cam sync sensor go bad but the symptoms for both were random engine shutdowns, not the ticking issue you are experiencing after your engine goes into closed loop. Both issues threw trouble codes also. I'm not saying these issues couldn't cause your ticking issue; they just did not for me. It was either it ran, or didn't. The 91-92 MJ distributor cam sync sensor requires complete disassembly to change. You have to remove the distributor and pull off the drive gear and shift to change it - PITA. A great upgrade is to junk this distributor and replace it with one from a 1994 model and up. The sensor is right on top under the cap so there's no disassembly of the dizzy required to change it. 94 and up Jeep 4.0 distributor 91-92 Jeep 4.0 distributor Link to comment Share on other sites More sharing options...
kryptronic Posted January 7, 2018 Share Posted January 7, 2018 8 hours ago, HOrnbrod said: both were random engine shutdowns, not the ticking issue you are experiencing after your engine goes into closed loop. Both issues threw trouble codes also. A great upgrade is to junk this distributor and replace it with one from a 1994 model and up. My experience was rough/eradict idle after reaching closed loop with no codes. No ticking though. +1 on the 94-95 distributor. Thats what I popped in for a fix. Link to comment Share on other sites More sharing options...
cjomanche Posted February 23, 2018 Author Share Posted February 23, 2018 Ended up being the distributor Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 24, 2018 Share Posted February 24, 2018 23 hours ago, cjomanche said: Ended up being the distributor What did you do? Replace it? Crushed wires where the harness goes in under the cap? Replace he sync sensor? Link to comment Share on other sites More sharing options...
cjomanche Posted May 15, 2018 Author Share Posted May 15, 2018 On 2/23/2018 at 4:40 PM, HOrnbrod said: What did you do? Replace it? Crushed wires where the harness goes in under the cap? Replace he sync sensor? Sorry for the late reply. Replaced the entire distributor. Been running like a champ ever since. Link to comment Share on other sites More sharing options...
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