Hello, A while back I had a situation where I slowly went over a speed bump and at that moment my check engine light came on and I had a loss of power. I ran the codes and they came back missfire on cyl 1 and missfire on cyl 3. I read online that a BLINKING check engine light means you are continuously getting a missfire and that it is normally related to the ignition coils. I replaced the coils on cylinder 1 and 3 but it has not resolved the issue. Is there anything you would suggest checking next? Been dealing with this issue for quite a while now.

 

ICM - ignition control module?
maybe you hit and theres a short in the system try and read with a multimeter

 

I'm planning on testing this tomorrow. Is there anything else you can think of that could 'jar' and screw up? After replacing the coils the CEL stopped blinking for about a minute but then it came back. It makes me think I am closer, but, its expensive to debug the isue $200 at a time

 

New spark plugs in general?

 

replaced all four when I changed the coils. I must be an electrical idiot and i'm not figuring out how to use a multimeter to test the ICM. I set it to resistance (2000) and place the red lead on the middle pin of the input side (the five plugs) and test the resistance of the four output pins with the black pin. I get a read from the first pin, the third pin and the fourth pin at about 520-530 but nothing from the second pin. I don't really have any confidence that actually told me anything.

 

Fixed the issue! it was indeed a blown ICM. It turns out when the previous owner installed the radio, he ran a direct wire to the same fuse that runs the ICM. It had an exposed wire and it looks like going over a bump would cause it to touch other electrical equipment. I believe this is why going over a bump caused the ICM to short out.

In the case of figuring out how to test the ICM, i used this:

http://forums.audiworld.com/showthread.php?t=211086

which indicated to test them in an 'X' pattern.

 

I remember seeing a post a while ago that was a pretty good write up with photos of how to test an Ignition Control Module. I used it to diagnose my misfire problem. I've actually had to change the ICM twice in the last 5 years. I don't know why they're prone to failure, but the posts said that it's a very common problem that usually shows up as a misfire in cylinder number 2.

Pete