I have a 1994 deville concourse - It runs rough.
I replaced the MAP sensor and replaced the spark plugs.
The converter has been beat out by previous owner.
When I pull the 4&6 plug wire it does change how it runs.
No codes
So how do I check if this is a coil pack & Spark, or fuel injector?
Thanks
David

if 4 and 6 are both on the same coil pack that might be a hint. does it run better or worse with those plugs pulled?

Make sure your plug wires are connected like this: (click and scroll in). (Northstar only....)