For the past 8 months i have had misfire issues with my car. i replaced the plugs, wires and 2 coil packs. then i replaced the ICM with 2 i have bought from the junk yard. every month i am changing the ICM with the 2 i bought from the junk yard and the original one. qafter a month it runs fine then misfires so i replace the ICM and misfires are gone. a month later the same problem i change the ICM it runs fine. I do this every month now. its hard to believe i picked 2 faulty ICMs from the junk yard. i dont want to spend $150 on a new ICM if this problem is going to happen again. is there any other know issues that cause the ICM to crate misfires? possibly a bad signal from a faulty cam, crank, or TPS sensor? just throwing out ideas
When you replace the ecm you are clearing the memory of the unit. that is why it will run good for a short time then the ecm will record trouble codes , turn the light on and go into limp home mode. start by having your codes pulled . I would stay with the ecm that should be in it. ecms are flashed to be vehicle specific
OK, the proper way to test that system is via load. Yes, changing the module and coil packs see,s to change stuff, but we need to know what it can and cant do. a 30kv test plug would be really nice to have. If all coil towers can CONSISTENTLY jump 30kv, then the problem isnt in coil. However, if the plugwires leaving a coil have 30,000 ohms of resistance (And they can be high resistance and still look like new!) then they will make the coil work 10x harder than it should to jump the spark gap...and the coil and.or module will fail over and over...but take months to do so, Also, a bad ground can lead to early coil and module failure, improper cooling, loose mounting bolts, high voltage from the alternator. a current probe and a labscope would help determine what is going through the coil vs what is coming out., an ICM is just an on-off switch for the coil packs and a buffer for the crank sensor signal. They generally fail 2 ways, hot misfire/stall/no start till it cools, or completely dead in the water no starts.
Coils generally fail 1 way, they draw too much amperage and they overheat the ICM and cause it to fail early.
changing the ICM via musical coils is not a good test. You need to know what is happening when it fails, and determine why swapping a previously removed ICM temporarily stops the misfire. Is the car losing spark? Fuel? Timing? does the connector have greenies in it? does the engine ground strap and the main ignition ground loop both show zero volts of voltage drop?
If the above doesnt help narrow it down, it may be cheaper to pay an expert who has access to labscopes and current waveforms to diagnose it before you purchase any more parts.
If any of the ignition components fail, you should get a check engine light and a trouble code for that component.
Are you getting any codes ?
Yes p0300 random multiple cylinder misfire . I cleared the code yesterday after I switched out the icm and the MIL has not come back on. After a few weeks the car will misfire, the mil will come on with the same code then I change the icm again. I repeat this process every month with any one of the three icms I have
My first thought is the module is getting too hot for some reason. Or one of the coils is breaking down and causing problems. But a coil would not come and go. Is there a chance something is wrong with the wiring plugs for the module ? Moisture or corrosion ? Or oil leaking around the module ?
Other than excessive heat or a bad connection I can't think of anything that would cause a partial failure and then be ok again.
Connection is good no loose wires. No oil or corrosion
I can't think of anything else either. Im going to the junkyard tomorrow and getting another icm. I might pull one off of a super charged 3.8l and see what happens
the plate that the icm bolts to on my 01 lesabre wasnt grounded properly and was eatin up an icm per month. took off cleaned real good and bolted back on, getting a damn good ground now and should be good to go
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SOURCE: replaced ignition control module on 1994 buick
check fuel pressure are fuel rail? Should be 40-47 psi. Also check filter at rear frame rail near RR tire, pull vacuum line off fuel pressure regulator at intake mainfold. Should have vac. and be dry, no gas at fitting.
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