I've had the 2nd 3800 motor running in my car and have been driving for just over a week. With the first 3800 series II NA I installed, I had a variety of missing problems which turned out to be ignition coils. I replaced all 3. With the new motor, everything seemed to be fine until yesterday. Starting yesterday, a miss has come back and this time the tachometer bounces when the miss occurs. As I continued driving, it seems that is progressively getting worse. These symptoms seem to indicate the Ignition control module because the module provides the tach signal, but before I go and blow $150 are there any other suggestions or possible causes for a miss and a tach bounce. I also have the module and coils mounted in the original spot, except mounted by one bolt instead of 2 in order to clear the hood bracket. Is it possibly just too warm in this location for the coils and module?

Some additional info: The new motor is a series III with the aluminum intake. I am using series II electronics and series II injectors. The coils and ICM are series II as well from my first motor. That motor spun a rod bearing this past spring

[This message has been edited by FieroFish (edited 08-21-2011).]

How are the plugs and wires?

The new motor has just over 4000 miles on it, thus I'm fairly certain they are in good condition. I haven't been able to dig in and check plugs or anything yet...I will also be doing that before I would replace the module.

It could be a pick up problem also. Is your MIL light hooked up? Have you scanned the PCM for trouble codes?

How regular is your miss? Do you have some separation between the high voltage secondary wires and the primary wires leading to the ICM?

My MIL light is hooked up and is lit up. I have scanned for codes after putting the motor in, but had not had the chance to scan again after todays issues. There were no ignition related codes, and everything ran great for a week. My girlfriends Honda accord had a similar issue and it was the distributor/ignition control, so I thought I would just ask for input on the idea. I haven't had time to dig into it and troubleshoot yet. The miss is getting more frequent. After first start up when cold, it runs fine for a few minutes. Once it heats up though, it starts missing and the tach bounces. by the time I got home this afternoon, the car was stumbling under acceleration and missing at idle. At idle the tach bounces lightly, under acceleration and heavier missing, it bounces significantly more.

As to your last question, pardon my ignorance, but I am somewhat confused as to what would be the primary and secondary wires. high voltage secondary are spark plug wires correct? On the 3800, the only wires are the spark plug wires and then the ICM connector plug. If you could fill me in as to what you are referring to that would be great.

I was not driving a 3800, but I had the same problem last year. It was my distributor's pickup coil.

Good luck!

Spark plug wires are the secondary. They should have some physical separation from the ICM primary (input) wires.

Today had a few minutes and had a chance to scan it. Its giving the P0336 code, Crankshaft position sensor. So...I'll start there, pull the wiring a little and see if I can find anything. I found other threads where there was some discussion that even with this code, problems still could be ICM or wires, coils, etc.