94 Z28 stalls/stops running when warmed up
07-18-2014, 06:16 PM
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94 Z28 stalls/stops running when warmed up Haven't been on here in awhile and did the search function but no luck.
Picked up a 94 Z28 6 speed late last year cheap cause previous owner said car wouldn't run. Charged battery and car ran great!
But a few months back the car would stall and not run when it warmed up. Had to what till it cooled down to start again.
I guessing back coil/ICM? The car runs great up to the stalling part, doesn't break up or misfire. It's not throwing any codes too.
Any help will be appreciated.
Picked up a 94 Z28 6 speed late last year cheap cause previous owner said car wouldn't run. Charged battery and car ran great!
But a few months back the car would stall and not run when it warmed up. Had to what till it cooled down to start again.
I guessing back coil/ICM? The car runs great up to the stalling part, doesn't break up or misfire. It's not throwing any codes too.
Any help will be appreciated.
07-18-2014, 06:46 PM
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If you replace it, do the washer/spacer mod to it. (place a washer or 2 between the ICM bracket and the head on each bolt)....the air gap keeps it cooler than being bolted directly to the head.
from shbox.com
Some people have reported ignition problems that seem to be heat related. One item that can be relieved of some heat stress is the Ignition Control Module (ICM). Merely spacing the coil and ICM bracket away from the cylinder head has solved miss problems in some cases. Any time you can reduce the amount of heat in an electronic component, it will normally prolong it's life and allow for more stable operation.
Getting to the coil and coil replacement is covered elsewhere in my Tech Pages, so I am not going to step through that procedure.
On my 1995 Z, I used a very simple approach to creating some space between the coil bracket and the head. I used some common 3/8" flat washers that I already had laying around. After removing the coil and studs, I put 2 washers between the "stud nut" and the cylinder head on the inboard stud. There is also a bracket for the EVAP hose that goes on this stud to take up some room. I used 3 washers on the outboard stud. With the thickness of the washers I had, this made the distance on each stud approximately the same (approximately 3/16").
The washers are used, because without the coil bracket sandwiched on the stud, the threads would bottom out in the head. This just gives a little extra space, which is not a problem.
Once the washers are in place and the studs screwed back in, you can mount the coil on the outside of the stud nut, instead of the inside where it was before. Torque value for both the stud to head and the nut is 18 lb. ft.
The total gap came out to about 1/2". Note that one of the studs has more threads on the outside portion of the stud nut. This is the stud that goes in the outboard head hole and is longer to accomodate the ground straps attached to it.
Another note: 1993 owners may have a bolt instead of a stud on the inboard side and others may have identical studs on both sides. It really does not matter. The intent is to create an air space between the head and the coil bracket. A little ingenuity and a couple of additional fasteners may be needed.
Tighten up the fasteners and reconnect electrical harnesses and you are done. I don't have any dyno runs or temperature comparisons for before and after, but for next to nothing in cost, this mod can't hurt.
I am not the first one to do this and it could be done using other methods and materials (perhaps, even more effectively). This just happens to be the way I did mine.
Update: At least one person monitored the temperature of the ICM and the head after the mod. With the engine running, the ICM stayed cooler, but when the engine was turned off, the ICM did not dissipate heat as fast as the head did. I did not get any info on how long the ICM stayed hotter. I am just providing that for your information and you can draw your own conclusions.
5/10/2003
from shbox.com
Some people have reported ignition problems that seem to be heat related. One item that can be relieved of some heat stress is the Ignition Control Module (ICM). Merely spacing the coil and ICM bracket away from the cylinder head has solved miss problems in some cases. Any time you can reduce the amount of heat in an electronic component, it will normally prolong it's life and allow for more stable operation.
Getting to the coil and coil replacement is covered elsewhere in my Tech Pages, so I am not going to step through that procedure.
On my 1995 Z, I used a very simple approach to creating some space between the coil bracket and the head. I used some common 3/8" flat washers that I already had laying around. After removing the coil and studs, I put 2 washers between the "stud nut" and the cylinder head on the inboard stud. There is also a bracket for the EVAP hose that goes on this stud to take up some room. I used 3 washers on the outboard stud. With the thickness of the washers I had, this made the distance on each stud approximately the same (approximately 3/16").
The washers are used, because without the coil bracket sandwiched on the stud, the threads would bottom out in the head. This just gives a little extra space, which is not a problem.
Once the washers are in place and the studs screwed back in, you can mount the coil on the outside of the stud nut, instead of the inside where it was before. Torque value for both the stud to head and the nut is 18 lb. ft.
The total gap came out to about 1/2". Note that one of the studs has more threads on the outside portion of the stud nut. This is the stud that goes in the outboard head hole and is longer to accomodate the ground straps attached to it.
Another note: 1993 owners may have a bolt instead of a stud on the inboard side and others may have identical studs on both sides. It really does not matter. The intent is to create an air space between the head and the coil bracket. A little ingenuity and a couple of additional fasteners may be needed.
Tighten up the fasteners and reconnect electrical harnesses and you are done. I don't have any dyno runs or temperature comparisons for before and after, but for next to nothing in cost, this mod can't hurt.
I am not the first one to do this and it could be done using other methods and materials (perhaps, even more effectively). This just happens to be the way I did mine.
Update: At least one person monitored the temperature of the ICM and the head after the mod. With the engine running, the ICM stayed cooler, but when the engine was turned off, the ICM did not dissipate heat as fast as the head did. I did not get any info on how long the ICM stayed hotter. I am just providing that for your information and you can draw your own conclusions.
5/10/2003
07-19-2014, 11:45 AM
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ICM, and Opti have heat sensitive devices that can take u out like a switch. The coil could too but i think would have different symptoms. PCM can do it also but i suspect it would just stop completely rather than be heat sensitive.
I would start with the easiest parts to test first. Test the coil. Then have the ICM tested. Finally replace the opti. Dont know who makes a good opti anymore.
My vote its the opti. Ive had both opti and ICM fail on my car and the opti can be intermittant (though it can completely die also) with the ICM died and never recovered.
I would start with the easiest parts to test first. Test the coil. Then have the ICM tested. Finally replace the opti. Dont know who makes a good opti anymore.
My vote its the opti. Ive had both opti and ICM fail on my car and the opti can be intermittant (though it can completely die also) with the ICM died and never recovered.
07-24-2014, 08:25 PM
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I'm going to have the ICM and coil tested hopefully this weekend.
I've had opti problems before and this is not showing any signs of this.
I do have a new opti just in case!
Thanks for this info.
I've had opti problems before and this is not showing any signs of this.
I do have a new opti just in case!
Thanks for this info.
07-16-2015, 07:56 AM
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Hi I know its been a long time since this was posted, but what did you find out? I am having the same problem. New PCM,ICM,Coil,Coil wire, fuel pump x2, TPS, water pump temp sensor, MAF,all injectors pulled and cleaned. The only thing different is mine when it dies it says check gauges. Fuel PSI 40 and stays there. I can't scan it will not connect and the fuses are all good. Tried to use a jumper and all that will do is turn fans on. Thanks in advance for any help.