2003 Buick Lesabre

Code - P0300 - Random Misfire

-Cat and exhaust clear.
-Replaced a bad Plenum gasket that was leaky.
-New plugs. New wires.

Upon checking for spark, cylinders 1 and 4 were not getting spark. I picked up a new coil and replaced. Still no spark. Cylinders 2,3,5,6 are all getting spark. So the other two coils are working fine.

Could the Ignition Control Module send spark to 2 of the coils and not 1?

 

I found a great resource while researching this.

http://easyautodiagnostics.com/index...articles_1.php

This website has a list of diagnostic steps for the 3800.


http://easyautodiagnostics.com/gm_ig...n_module_1.php

^ This one in particular goes through the steps to determine where your misfire is.

I tested the ignition coil module to make sure it was getting 12 v. It was. I then used an LED light to test the module to see if the switching was turning on. It wasn't.

2 of the towers were switching and 1 wasn't leading to cylinders 1 and 4 misfiring. I will be replacing the ICM. Which is quite costly.

 

A smart move would be to replace it with OEM parts, AC Delco.

 

Well it's great to see Imadozer is still with us, as he always gives great advice. Firstly itis hard to point a direction to start without a code, until I read the whole question I was ready to reply with the idle air controler, but when he is accerating that didn't apply, I have had a similar problem that ended up with the plug wires, the carbon pile inside hardened up right at the spark plug end of the boot and created the same problem..(actually at 2 of the wires). So until we get a code to get a direction where to begin throwing parts at it won't be the best place to start. There was another incident that created a similar problem in the past and that was the little rubber elbow with the vacuum line that went to the modulator on the transmission that had dried out and split and made it lose the vacuum and caused the bad idle condition, but there wa an indicator light with a (P) or permanent code without an explanation, and if this helps I'm all for looking into that, as it's an easy fix as is what I'm responding here with, good luck in any case. By the way that LeSabre had 250,000 miles on it at the time.