test for ignition control module

[Larry Larson]

Hi,
Is there a procedure posted somewhere for testing the ignition control module? I did find the one for the coil packs.

Also, I will soon be testing the coil packs. If I replace them should I replace the ICM too? I know a bad ICM can damage the coil packs, but I'm wondering if the reverse is true also.

thanks...

[91NinetyEight]

Some parts stores can test the ICM and coils, I'm not aware of a DIY test procedure for the module.

[Bing]

Unfortunately testing the ICM can be a crap shoot. Some ICM's will test bad when they actually are good and some test good but they are bad.

What kind of symptoms are you experiencing, or do you have a CEL?

[Larry Larson]

No CEL. Symptoms: The car runs OK at any steady speed. When I accelerate, its sputters and misses. This sort of thing has happened 3-4 times in the last year, and each time I replaced something that made the problem go away. The first time it was the ECU, next time the crank angle sensor, next time the battery, last time, catalytic converter.

I'm suspecting an ignition issue as opposed to fuel pump because if I'm going 60 it stumbles if I hit the gas, but if I downshift one gear before I accelerate, it does better.

[Bing]

Ok just throwing this out there, what about the fuel filter?

You could also hit up the junkyard or pick a part for a spare ICM or two, and test that option out.

[Larry Larson]

forgot to mention that I changed the fuel filter.

[Larry Larson]

So, if my coil packs test bad, should I just go ahead and replace the ICM too, since there's no reliable way to test it?

[Wes]

I personally would not change a working ICM.

Are you saying you already tested the coils and they failed? Or was that just a hypothetical question? Because it is usually just one that fails at a time.

[Larry Larson]

It was hypothetical, I have not tested them yet. My concern is that bad coils might be able to damage the ICM since I read that a bad ICM could damage the coils. I didn't know if it worked both ways.

[Wes]

I'm guessing this is a crank but no start situation. In my experience with these cars, one will go and you will run on 4 cylinders. 1 coil failing will not stop the spark of the other two. Have you checked the spark of all the cylinders of the front bank?

[Larry Larson]

Wes, see my previous post where I describe the symptoms. I have not checked the spark on the front bank because that would be hard to do while driving! It starts fine, idles and revs smooth until under load.

[myfirstbonnie]

Most of the time this ends up being an ignition problem. Start by checking the coils as described in the Techinfo article and go to a JY and get another ICM. If the coils check good, put the new/used ICM on and see how it does. If you find a coil to have a significant amount of change, then replace it. Coils are also readily available at the JY.

Make sure you remove the coils and check both windings.

[Wes]

No CEL. Symptoms: The car runs OK at any steady speed. When I accelerate, its sputters and misses. This sort of thing has happened 3-4 times in the last year, and each time I replaced something that made the problem go away. The first time it was the ECU, next time the crank angle sensor, next time the battery, last time, catalytic converter.

I'm suspecting an ignition issue as opposed to fuel pump because if I'm going 60 it stumbles if I hit the gas, but if I downshift one gear before I accelerate, it does better.

doh, sorry. I read your first post time looking for sypmtoms, and seemed to skim right past them.

From that description, I think you are on the right track by testing the coils first. Usually when the ICMs fail, they take out the ignition all together and not select cylinders. Let us know what you find once you have those check out.

[pbrktrt]

When is the last time plugs and wires were changed?

[Larry Larson]

both changed recently.

[Larry Larson]

Embarrassed but very happy. Even though I replaced the plugs and wires only 20K ago, I pulled a plug today to look at it. The gap was huge. So I replaced the plugs and wires, and it runs great.

No excuse for not suspecting them earlier, except maybe that in the past I had 3 Japanese 4 cylinder cars that I drove over 200K on the original plug wires, and only replaced the plugs every 40K and they ran great. Maybe a supercharged engine is harder on plugs?

Anyway, I'm a happy boy, I've got my scalded cat acceleration back!