Please help, i have a 2003 Buick Lesabre I've been working on. Its a no start most of the time but once in a while it will start. Not reliable enough to take anywhere and last tim i was able to get it started I smelled what i could only describe as burnt popcorn. Anyways, I checked the ignition coils and they are all good. I bought new coils, spark plugs, and wires. However the bottom coil is not firing. Before i go and spend $100 on a new icm, I was just wondering is anyone on here could confirm that it might in fact be a bad icm. The top 2 are running and firing I assume fine. they fire and I am just guessing that they are firing on time. Thank you ahead of time.

 

Remember the coil gets its signal from the icm that gets it's signal from the crank sensor. Starting from the beginning, make sure there are no apparent problems at the crank sensor reluctor which is behind the crank pulley. every so many teeth the signal from the reluctor triggers the icm that triggers the coil in question.

 

I did go ahead and purchase a crank sensor since i found one on rockauto for only a few bucks. I haven't put it in yet an will probably install tomorrow morning. i also ordered a cam sensor. I saw a few things online saying that could be the issue so i ordered it as well. I wish i could read the odb port but the port keeps giving me a link error when I try to use my scanner. Anyways, i will update tomorrow if the problem continues. I wasnt sure if a bad sensor could only cause one of the coils to not fire. I figured that the sensor going bad would cause all the coils to not fire or atleast not only the bottom one. Also, if the icm is bad, could it only quit one of the coils? Im new to cars and this is the first time i've really repaired a car other than changing tires if that could be called repairing. Just kind of learning as I go. Thankyou so much!

 

Before diving into replacing the crank sensor (some combine cam and crank sensors) I would suggest you do some homework and read up on what is required to replace that sensor. It involves removing the R/S front wheel, inner fender, and crank pulley.after you have the vehicle up on jack stands. You may need a special puller to remove the crank pulley. Not a small job on this vehicle.
Personally I would rather take a chance at replacing the ICM before going through all the trouble of possibly replacing a good crank sensor.

Reminder; I suggested you check the reluctor BEHIND the crank pulley that triggers the sensor. Look for a possible bent tooth.

 

I had same exact issue on my 03 lesabre. New delco icm and it's fixed. When replacing icm, use thermal paste on the bottom. It's a better heat conductor then anything else. A nice thin coat and also clean the the bracket it attaches too.