Ok, I have been chasing down a mis for about a week now. First, I thought it was something with the cc carb (1987 Z28 with Q-jet) like the MC solenoid. I thought the carb because the O2 sensor was showing very lean. Was not that.

Next, I started looking into the ignition. I have a Mallory box with Crane plug wires rated at 25 ohm. First I changed plugs and just put in new AC Delco's. That did not fix it, so with pliers I started pulling off each plug wire at the distributor and watched how the engine reacted. When I pulled off the #4 cylinder, I saw essentially no change in idle.

Therefore it leads me to believe something is wrong with the plug wire, but when I check the resistance, the total wire is reading 150 ohm, which is probably about 75 ohms per foot. Not bad enough to cause a mis?

So what do you guys think is going on? The wire looks perfectly fine and has not be burnt by the headers.

Any advice?

 

Check the spark plug itself and the distributor cap.

 

Yeah, I replaced the plugs and that did not help. However, as I was swapping the plug wire with one from an old set, the terminal on the distributor pulled out. Problem found. I temporarly inserted the terminal to be able to drive the car today and it works fine. I guess the terminal had worked its way lose and was not lining up with the rotor properly?

Anyways, the dist cap was just a cheap AdvanceAuto piece. Any suggestions on a good brand?

 

AC Delco or any replacement brand that has brass terminals (the cheaper ones have aluminum terminals).

 

Autozones Conrad cap and rotor set are high quality. I have one of my 383 with full MSD setup and it has performed flawless for the last 15K miles. All brass terminals too.

 

Don't buy cheap ignition parts or any other parts for that matter. Bosch makes good caps, so does GM. Any others I've tried were garbage including Accel. MSD is the only one I haven't tried. Might be ok. They are known for quality.