Hello my 1983 FB Rx7 has emissions delete, Holley 600 DP, Holley fuel pump, RB intake, dual MSD 6al ignition and coils, Bridgeport 12a. Sometimes my car will run fine on all 4 plugs and randomly it will jump to 3 and my rpm gauge will not work when it does happen. I was told to replace my spark plug igniters but I don’t have them on my car, does anyone have any input on this thank you

 

Wow, what makes you say you're only getting spark on 3 plugs??? Have you pulled the plugs and wires off, cranked it and seen spark on only 3 plugs? How else would you know this? What are the symptoms? Which plug has no spark?

 

There are two igniters. One for leading plugs and one for trailing. If both trailing plugs weren’t firing for example you might have a bad igniter. But if only one plug isn’t firing then the igniter shouldn’t be the issue.

It would have to be an issue with the plug itself, the wire, or the distributor (bad cap?).

This assumes you’ve taken the plugs out and checked for spark. Having only a single plug not firing is a weird issue