Cars, etc.

[Id_Jit]

BD, did you actually switch the coils?

Make sure that the plug wire for #1 cylinder is properly seated at both (coil and plug) ends, and as Larry said, make sure that it is properly dressed in the wire loom.

You might want to pull spark plug #1 and check it for a proper gap.

Back to Larry’s suggestion. start the car up at night and look for any arcing on the plug wire etc. for #1. Take a spray bottle with tap water in it and LIGHTLY Mist the coil, wire and plug. Watch for any arcing.

Check for a bad intake gasket to cylinder #1. This can be done by carefully spraying carb cleaner around the gasket between the intake manifold and the head with the engine idling. Use the little tube to direct the spray ALL around the gasket. WD-40 or Throttle Body Cleaner? also may work here. If the idle picks up then drops after you stop spraying, you have a bad gasket.

Kinda OT: Fuel system cleaner… I presume that you mean fuel injector cleaner.
I’ve used twice the recommended `dosage’ in a full tank of gas in my now defunct Civic (10 gallon tank) I’ve read on Passat World a recommendation to use a double dose of Techron in a half tank of gas. Drive it until the tank is 1/4 or less, and then fill the tank with another double dose. I doubt your problem is a dirty injector, given your cruise control problem, but it is from the “Won’t Hurt Department”.

Id