GM 3800 ICM not working after spark plug and wire

[rkpatt]

I just changed the spark plugs and wires on my 1999 GM 3.8 . The engine ran briefly then died . I went through a diagnostic procedure and and determined that the ignition control module (ICM) was bad. I did not check the gap on the plugs before I installed them but later found out the gap out of the box was too small. The Autolite wireset seemed to be fairly close to the original in length wires on cyls 3 and 5 were slighty longer than the original . Would either of these (small plug gap or wrong wire length) cause damage to the ICM ?

 

[rkpatt]

BTW- the gap on the plugs out of the box was 0.035 . THe sprec is 0.060

 

[The_Eric]

The too small of a gap shouldn't have killed the ICM. If you're sure it's the ICM and not something else, like a crank sensor, then check the wiring harness at the ICM, the grounds below it on the stud and also remove the ICM and check for corrosion between it and it's mounting plate.

 

[Nyquist]

Verify you have signal & power going to the ICM along with verified reference voltage (5V) at your sensors. As stated above the crank sensor could be bad.

I seem to recall on some 3.8L that were supercharged that there is an error in the Mitchell & Haynes books regarding spark plug wire placement. I can't remember the model years off the top of my head, but I believe it was late-90s an caused a severe misfire and/or no-start.

 

[sciphi]

Make sure the wire to the #6 cylinder is not anywhere near the primary oxygen sensor. It will cause running issues. If it's touching the sensor, it will throw off the reading and make the engine cough or even die the second it switches to closed loop. That takes about 30 seconds to a minute after a cold start.

And, are you sure you routed the wires correctly? I incorrectly routed the wires once on my old LeSabre with the 3800, and it had a big miss until I routed them correctly.

 

[rkpatt]

I will remove the ICM and check for corrosion .

BTW- No spark on coil pack 3/6 . Intermittent spark on others.

I diagnosed the ignigition system using this procedure - http://easyautodiagnostics.com/gm_ignition_3800/test_ignition_module_1.php . CPS checked out ok and it appears to be a bad ICM .


I am tempted to go back with my original plugs and wires (the were not that bad and the car ran fine) just to see what happens.

BTW- BTW- No spark on coil pack 3/6 . Intermittent spark on others.
The spark plugs I bought were Denso PTT16TT 4511, wire set Autolite 96650

Thanks