Strangest thing I've ever seen in 45 years working on cars on a 1991 Olds 98.
 

I have a 91 Old's 98...Series 1 3800 non-supercharged.......... when the engine is cold it will not start BUT if I put a spark tester on the 1, 3, or 5 tower on the coil it'll start...... THEN when the engine gets to operating temperature the engine will run without the spark tester in place BUT it will not start/run until the engine warms up......... ANYONE dealt with anything like this? I even moved my grounds to see if it was a grounding problem.......still no luck..........

Sounds like the ICM or maybe a connection under the coils.

ICM is known to do this.

Can you explain why? This is a brand new ICM.... I guess I need to take it up and have it tested.....
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Clean the grounds (plate and bolt holes) for the coil pack/ICM.

Done it..... no luck but with my volt meter I'm getting good ground.