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Tom in NH

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  1. Hi Moses, Spent the last couple days tracking and tracing everything I could. Narrowed the major draw down to what appears to be the ignition switch. I got a draw (bright light)at the alternator, but not the thick red wire going to the single post. That tests fine, but rather at the brown/tan resistance wire which according to diagrams I have seen leads to yellow ignition wire and what I have read suggests a faulty ignition switch. Also got a draw at the green lead running from the hot post on the starter relay which again, diagrams say leads to ignition. Have just replaced ignition switch, cleaned up as many grounds and wiring issues as I can find including all major grounds - some of which definitely needed cleaning. I still get a dimly lit test lamp. Using your scratch test, I get a very faint hard to detect spark. Used to be a rather pronounced "pop". I am guessing zero draw is not possible as I have a working original analog clock and the ecm needs some level of current to hold sensor settings, so I am hopeful the much improved and smaller draw is roughly within spec. Will connect everything back up and I guess ultimate test is let Jeep sit overnight or two and read battery voltage in the am? Thank you
  2. Hi Moses, Thank you for your full and complete responses. And yes, you mentioned the battery right up front. Had it tested, thought all was good.... Update. New battery shows 11.9 volts this am. Given your explanation, believe we have found the smoking gun. Now have to find the actual culprit. So, that means battery drain when Jeep is "off", correct? To confirm, with Jeep in off position I disconnected ground and ran a test light from ground cable to neg post and it light up. So, now I disconnect accessory cables at battery (we have 2 led light sets and an oversized positive lead for audio amp - I think I should check those first) one at a time until light goes out? If light stays lit, I move on to fuse box and disconnect one at a time? Any shortcuts or am I on the right track? Again, many thanks - as I mentioned electrical is always something I avoided. So I've got a learning curve here.
  3. Hi Moses, Yes, double checked the scale on the multimeter when I checked the lead from ecu pin 27 and it read a legit .5-,6, but what you say makes sense. My multimeter is a relatively cheap version and is digital. I have read that analog meters are sometimes better at reading signals that change quickly. Idle didn't change after cleaning cps, but it was idling well prior. The Jeep runs quite well ... until it stumbles which is sporadic and infrequent. Even less frequent stalling and no start immediately after stalling only a couple of times in the last 6-9 months since this issue was first detected. Each time there was a no start, I replaced the coil and icm, cleaned cps, but have not ever replaced cps. Resistance on cps is about 206 cold and 244 hair dryer warm. New info - checked battery last night and got a reading of 11.9volts. It did start and I checked with Jeep running and alternator and got 14.4. This morning battery reading of 12.1. Weird, as I had battery and alternator checked at one of the chain stores. Battery was 7 years old, so Got a new battery today. All seems well and alternator still checks good. Thank you
  4. Hi Moses, OK, backprobed the orange wire at the ICM that connects to pin 27 on the ecu. When running, I get a kind of bouncy reading of between .5 and .6 volts. No pattern or regular timing to the variation. So if it is supposed to be a 5 volt sine wave, I'm assuming that means I should get a 5 volt reading alternating with zero at regular intervals? Also pulled my cps and it was oily like it usually is when I check it. Cleaned it and area around it, retorqued valve cover. Ran it for a good half hour, and even though the coil is getting 14+ volts at the + lead, it was not hot I would say just warm to the touch. Keeping my eye out for a used FSM. Thank you
  5. Moses, Another thought. So, if 14+ volts on the yellow lead to the ICM is normal and expected, then is it possible the Autozone brand ICM could be the culprit and is just not up to the task? As they are warrantied parts I have been simply replacing with the same. Because, as I think this through, I am also getting 14+ volts at the + lead of the coil, so the ICM is not doing anything to step the voltage down before it sends the power to the coil. Like I said, electrical is not my strong suit - swimming as fast as I can here to keep up, but learning and enjoying it. Thank you.
  6. Hi Moses, Wow. Thank you for the thought and detailed comments. A lot here. A few comments and then I will test what I haven't yet tested and report back . With key on, engine not running, I get 12 + volts (basically static battery) at connection A (yellow lead) and at the + lead on coil. With engine running, I get the 14+ volts at both. I was aware of the 5 volt sine wave function (though didn't really understand it's operation until your explanation - electrical is not my strong suit), but I have not tested it running. I got zero volts at key position run with jeep not running earlier - now I know why. I will back probe it and test and report back. I have replaced 3 coils and 2 icms. The last 2 replacements have been both together as a unit. I replaced the original o2 sensor with an off brand a while ago, but in reading other threads of yours, realized it probably wasn't a good fit. Have since replaced it with an NTK, which I understand is appropriate. Other sensors have tested good (TPS, MAT and MAP). tested EGR solenoid and it tests good. Replaced the EGR valve as it was original andrusted, filled with carbonized crud, etc. All of these things have resulted in Jeep running quite well. However, it just stumbled yesterday for the first time in a couple weeks, which tells me the issue is starting up again, which makes sense. It is interesting what you say about the Idle Air Control Motor and the CPS. I check the CPS periodically and it is almost always oily. (valve cover has a crack at one back corner bolt hole). I clean it and replace. Didn't realize that could cause issues when hot. Very interesting. Any fix (besides trying to keep it from getting oily)? I replaced the IAC motor and regret it. Should have cleaned and rebuilt the original- which I may still do and reinstall. The newly installed IAC seems ok, just not sure it is bang on. I guess I have been assuming that there was a failure on the ecu relating to pin 27 or pin 3. I haven't found an option for repair of the ecu and thought a ceramic resistor installed on the yellow lead (connection a), while not part of the original set up would at least reduce voltage to coil to keep things functioning and not frying coils/icms. I guess a reading of the orange lead from pin 27 to the ICM while running will help clarify that?
  7. Hi Moses, Thank you for your response and thoughts. Some more info and answers to some of your questions. I am reasonably sure the grounds are good. Will check in the am, but went through them after reading another thread on your site when this problem first cropped up. I paid particular attention to the ground by the dipstick. I also added grounds a couple years ago and checked and cleaned those. I have had both battery and alternator tested at autozone and they check out good. I am on my 3rd coil in the last 18 months (warranteed, but still ...). This last one is what got me to searching for the cause and today found the constant 14 volts. My understanding is that line voltage (12-14+ volts) passes to the coil at crank, but the ecu is then supposed to step the voltage down to less than 9 volts at run. Is that correct? If so, then my constant 14 volts at run means some defective circuitry on the ecu and my problem of frying coils? Could the ignition switch play any part in this problem? It appears to function properly. No problem at crank jeep starts well (and runs well until coil degrades over time and then stalls/misbehaves when hot). All accessories run and work properly, tach functions properly. I'm inclined to look to the ecu, but a new ignition switch is much cheaper than a reman ecu. I will check more voltage and resistance in the morn. Thank you.
  8. Greetings, Have a 1989 YJ with the 2.5l TBI. Have had a sporadic idle, stall problem. Verified fuel delivery and injector performance, tested and/or replaced all sensors and IAC motor. Cleaned throttle body, checked for vacuum leaks. Kept looking over at the coil/icm assembly, but thought "no, just replaced those not too long ago." Long story short, tested the coil - badly out of spec. Changed out both coil and icm and finally (slow learner here) checked voltage entering coil. Constant 14 =/- volts at startup and run. Checked with my daughter who drives the vehicle and she confirmed after pondering that yes, seems to only happen after driving for quite a while - giving the icm/coil plenty of time to get nice and toasty. So, I'm guessing that means ecm troubles, as I know this problem has popped up from time to time but am wondering if it is possibly an ignition switch issue? So, I'm checking with the experts before I choose which pain in the butt part to remove first. Thank you.
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