mfendley Posted October 2, 2018 Share Posted October 2, 2018 Son's 91 Comanche 4.0, 5-sp. Runs well when cold, but dies after warming up (5-8 minutes driving). Gauge is in 175-185 range. Have replaced ECU, distributor, coil, wires, plug, CPS on electrical side. Replaced fuel pump and filter on fuel side. When driving, it almost feels like someone is turning the ignition off, and then back on immediately. First it happens briefly, then gets more frequent, until the engine dies, leaving the Comanche stranded on the side of the road. Will not restart until fully cooled down. Thoughts? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 2, 2018 Share Posted October 2, 2018 Check for trouble codes: Link to comment Share on other sites More sharing options...
bluenotenick Posted October 2, 2018 Share Posted October 2, 2018 I had a Honda that would do this. Replaced a relay and it was fixed. When the relay heated up it would fault out, only to work again after cooling off. Link to comment Share on other sites More sharing options...
mfendley Posted October 2, 2018 Author Share Posted October 2, 2018 Thanks HOrnbrod. I will check and report back. bluenotenick - which relay? Link to comment Share on other sites More sharing options...
bluenotenick Posted October 2, 2018 Share Posted October 2, 2018 It was an ignition relay under the dash, but it was an '87 Honda so the electrical is probably different on an MJ. Is there an ignition relay in the engine compartment on the MJ? My knowledge in that area is limited. Maybe someone else can chime in... Link to comment Share on other sites More sharing options...
kryptronic Posted October 2, 2018 Share Posted October 2, 2018 4 hours ago, mfendley said: Son's 91 Comanche 4.0, 5-sp. Runs well when cold, but dies after warming up (5-8 minutes driving). Gauge is in 175-185 range. Have replaced ECU, distributor, coil, wires, plug, CPS on electrical side. Replaced fuel pump and filter on fuel side. When driving, it almost feels like someone is turning the ignition off, and then back on immediately. First it happens briefly, then gets more frequent, until the engine dies, leaving the Comanche stranded on the side of the road. Will not restart until fully cooled down. Be thankful it's an HO Comanche, and you've got OBDI to help. Get codes, even if there is no check engine light, there still could be codes. Sounds like it's an electrical/sensor issue to me. The system goes into closed loop at 185 degrees, and that's the point at which the computer takes over. To my knowledge, restarting when hot (above 185 degrees) puts the system in close loop immediately, which could cause your failure to restart when hot. Beyond that, when you say you replaced the distributor, did you replace just the cap and rotor, or the entire distributor? I'm asking because the camshaft position sensor is in the distributor and can cause rough idle, but probably wouldn't cut the engine out. Link to comment Share on other sites More sharing options...
omega_rugal Posted October 3, 2018 Share Posted October 3, 2018 cps... Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 3, 2018 Share Posted October 3, 2018 A bad CPS would show up as a code 11. There's no reliable way to test the CPS on an HO except replace it. I've had this same problem engine cut-off problem at temp twice and both times it was the ignition coil. There was no OBD1 code either. The first time it was a cooked original Mopar coil, replaced it with an aftermarket Accel coil I had lying around. It too failed about a year later. OP, if you replaced your Mopar coil with a cheap aftermarket, this could be the problem. Hope you replaced it with an original Mopar unit. The ignition coil is stupidly mounted directly to the engine block w. no insulators and it bakes over time. On an aftermarket junk coil this time isn't very long. The best cure for this is here . If you can't do this, at least get the ignition coil off the engine block. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 3, 2018 Share Posted October 3, 2018 Good rule of thumb for early 90s HOs. If it has a Magnetti Marrelli coil, replace it. Link to comment Share on other sites More sharing options...
mfendley Posted October 3, 2018 Author Share Posted October 3, 2018 When I replaced the distributor, it was the entire unit. I have replaced the CPS and the coil, but the replacement parts were from Advance Auto, not OEM. I will look into finding better quality parts. Relocating the coil away from the engine makes sense, will try that also. Haven't had a chance to pull the codes yet, the truck is at a mechanic's shop I trust to see what he was able to find; nothing yet. I also purchased a replacement engine wiring harness (junkyard, but appears to be in good condition) as I read there can be issues between the harness and ECU. I appreciate all of the suggestions presented - I will report back what cures the problem. Link to comment Share on other sites More sharing options...
Zaptoo Posted October 5, 2018 Share Posted October 5, 2018 Does it start up after it cools down a bit? do you have to wait long? --Sorry OP reread your post, "Will not restart until fully cooled down.". -- It almost sounds like vapour lock, how old is your gas cap? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 5, 2018 Share Posted October 5, 2018 On 10/3/2018 at 1:21 PM, mfendley said: Haven't had a chance to pull the codes yet, the truck is at a mechanic's shop I trust to see what he was able to find; nothing yet. Tell your mechanic to check the codes then. He should know this. Probably save you some $$. Link to comment Share on other sites More sharing options...
mfendley Posted October 5, 2018 Author Share Posted October 5, 2018 11 hours ago, Zaptoo said: Does it start up after it cools down a bit? do you have to wait long? --Sorry OP reread your post, "Will not restart until fully cooled down.". -- It almost sounds like vapour lock, how old is your gas cap? Not sure of age of gas cap, but I am almost certain this is ignition related issue. Once the Comanche is up to temperature, it is like something is turning the ignition off briefly, and then it comes back almost as quickly. The instances are 30-45 seconds apart, but then starts happening more frequently. Once this has happened enough times, the unburned raw fuel in the exhaust ignites, and a backfire occurs with a visible flame out the exhaust pipe. If enough of the occurrences happen in a short period of time, the engine dies, and then is impossible to restart until the engine fully cools down. Link to comment Share on other sites More sharing options...
mfendley Posted October 5, 2018 Author Share Posted October 5, 2018 On 10/3/2018 at 12:19 AM, cruiser54 said: Good rule of thumb for early 90s HOs. If it has a Magnetti Marrelli coil, replace it. How is this coil identified? I think I will get a new coils, along with the kit to relocate to the shock tower, if I can find one. Link to comment Share on other sites More sharing options...
kryptronic Posted October 5, 2018 Share Posted October 5, 2018 6 hours ago, mfendley said: How is this coil identified? I think I will get a new coils, along with the kit to relocate to the shock tower, if I can find one. Look for it on the block near the distributor, in front of it. There will be a wire running from the distributor to it. Link to comment Share on other sites More sharing options...
cruiser54 Posted October 6, 2018 Share Posted October 6, 2018 10 hours ago, mfendley said: How is this coil identified? I think I will get a new coils, along with the kit to relocate to the shock tower, if I can find one. Has the name on it. Link to comment Share on other sites More sharing options...
Zaptoo Posted October 6, 2018 Share Posted October 6, 2018 5 hours ago, kryptronic said: Look for it on the block near the distributor, in front of it. There will be a wire running from the distributor to it. Oh wow. That's where they put the coil? o.o Mother of god that is a dumb setup Link to comment Share on other sites More sharing options...
Minuit Posted October 6, 2018 Share Posted October 6, 2018 9 hours ago, Zaptoo said: Oh wow. That's where they put the coil? o.o Mother of god that is a dumb setup The heat from the engine makes the sparks go faster! Link to comment Share on other sites More sharing options...
mfendley Posted October 6, 2018 Author Share Posted October 6, 2018 9 hours ago, Zaptoo said: Oh wow. That's where they put the coil? o.o Mother of god that is a dumb setup It's a lot easier to see here, since there is no AC compressor blocking the view. I has a NOS coil, bracket, and voltage-reducing harness on the way, should be here on Tuesday. This weekend I am going to work on the blower motor. It currently works, but only slowly. I thing I will get a new blower motor and resistor pack. Any tips on the blower motor? Link to comment Share on other sites More sharing options...
Zaptoo Posted October 6, 2018 Share Posted October 6, 2018 8 hours ago, Minuit said: The heat from the engine makes the sparks go faster! Link to comment Share on other sites More sharing options...
omega_rugal Posted October 7, 2018 Share Posted October 7, 2018 13 hours ago, Zaptoo said: Oh wow. That's where they put the coil? o.o Mother of god that is a dumb setup was so difficult to put an spacer so the coil doesn´t touch the engine, preferibly made of a non conductive material? Link to comment Share on other sites More sharing options...
mfendley Posted October 9, 2018 Author Share Posted October 9, 2018 On 10/6/2018 at 9:16 AM, mfendley said: It's a lot easier to see here, since there is no AC compressor blocking the view. I has a NOS coil, bracket, and voltage-reducing harness on the way, should be here on Tuesday. This weekend I am going to work on the blower motor. It currently works, but only slowly. I thing I will get a new blower motor and resistor pack. Any tips on the blower motor? Changed the blower motor and resistor, blowing much better - except that there is no high speed. Have Low, Med1, Med2, but no high. Will have to figure that out later. More importantly, I received the NOS coil and voltage reducing harness (no bracket, but I was able to re-purpose the old one. Relocated the coil behind the passenger shock tower. Still have the occasional miss, after the engine warms up. Did note that this only occurs over 2750 rpm; lower than that and it runs fine. Any other ideas? Still have to go check the trouble codes, will report back what I find. Link to comment Share on other sites More sharing options...
kryptronic Posted October 10, 2018 Share Posted October 10, 2018 Something happening after the engine warms up versus before is an indication of a sensor or computer related issue. Looks like you handled the crank and cam sensors. Did you clean the throttle body, TPS and IAC valve? Have you run vacuum and fuel pressure tests? Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 10, 2018 Share Posted October 10, 2018 1 hour ago, mfendley said: Still have to go check the trouble codes, will report back what I find. Please do before throwing more parts on it. Link to comment Share on other sites More sharing options...
mfendley Posted October 10, 2018 Author Share Posted October 10, 2018 No codes registered. Even though this truck is not driven often (my son's daily driver is a Renegade) it has been a couple of years since its last tuneup. Will get cap, rotor, wires and plugs swapped. Will also run some Seafoam or similar to ensure the injectors are clean. That way, I know that portion of the ignition has no breakdowns (shorts to ground). Link to comment Share on other sites More sharing options...
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