when coil fails the engine will start and run bad on the other 4 cyl. usually when the crank sensor goes you get no spark or an intermittent start then no start but when its not starting you get no spark. weak spark is really confusing, possibly the icm is bad. possibly bad ground.testing icm for 3800 but i would think its similar:ICM test
you should pull a inj connector you should have volotage on one side, then you can make a tester to see if you have the inj. pulse with a 12v bulb. run one wire to the 12+ the other to the inj connector, the pulse from the computer is the ground. with someone trying to crank it the bulb should flash.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock