Hello Scotty, 2003 Buick Park Avenue Ultra Supercharged 3.8 V6
there are all new wires on the vehicle and plugs are near new. Great spark from coils 1-5 but number 6 weak. Went to auto wreckers and got a new coil for it replaced it and same thing happening. Also replaced electronic control module and EGR which stopped the surging. Used heat sink paste to make sure of good connection on the module. I just can’t figure out why coil #1 has a weak spark. The number 4 on the same coil is strong. Car has done some rough starts at stop lights when accelerating from a stop.
thx
I'm a little confused. You started with weak spark on #6. By the end of your question the weak spark was on #1.
But it doesn't matter.
First, just because 1 of the 2 coil towers for the same coil has good spark doesn't mean the coil isn't defective.
The coil needs 2 things. 12 volts and a control signal.
Since the coil tower for the "paired cylinder" for that same coil is working, you know you have 12 volts and a control signal going to that coil.
The positions of the 3 coils on your control module are interchangeable. (Of course, if you have OEM coils that have the cylinder numbers printed on them, you'll have to ignore those numbers if you swap coil positions. The plug wires locations aren't interchangeable)
So to see if it's a problem with a coil, just swap position of the defective coil on the ICM with one of the other 2 known good coils.
If the weak spark follows the defective coil to the new location on the control module, then you know you have a problem with that coil.
(replace it).
If the weak spark stays at the same location on the ignition control module, then you either have a bad ignition control module or with the wiring going to it
