Re: V4 rough idle
I have been having intermittent spark problems with my '89 150 XP V-6. Just last night, I had a heck of a time getting it to start. Took a lot of cranking until it even fired (and it is getting plenty of fuel). When it finally did start, it was idling rough. I began pulling plug wires, one at a time, to figure out if all cylinders were sparking. If you hold your plug wire near the tip of the plug, you'll get a nice, bright arc that will jump from within the plug wire cap to the plug. I found that 2 of my 6 cylinders had no spark whatsoever. I shut it down, then started it back up (after it's been started, it fires back up very easily). I checked, and those 2 cylinders still had no spark. Then I shut it down, swapped plug wires and re-started, but still the same 2 cylinders had nothing (wires okay). Then I swapped coils, between one of these cylinders and another one that had good spark. When I re-started it, both cylinders that I just swapped coils on had good spark. Looks like a ground problem. I then removed both of these coils, cleaned up the contact area (one of the bolts has a metal contact on it to ground to the block). Now all 6 have good spark. May not be your problem, and I'm no mechanic, but something easy to try before spending a bunch of your beer money chasing this problem! Good luck.
