Another RB25 misfire issue

[joelg4461]

My rb series 1 starting misfiring on cylinder 5 and I have no idea why. I switched plugs and coil packs around to see if it would move but it didn't. So I bought a new fuel injector for that cylinder and still nothing. So I bought some new plugs, gapped them down to .028 and still misfiring. At this point I assumed the worst and ran a compression test. The numbers were a little low(probably my cheap compression gauge) but even all the way across. Nothing that would explain missing in only one cylinder. I have good spark in that cylinder and I'm at a loss. If it were timing or any sensor, why would it be only in one cylinder?

The original spark plug out of that cylinder was fouled, making me think it has been running too rich. How do I go about actually measuring the spark? I know it has spark but who knows.

Any help would be appreciated. Thanks fellow zilvilians.

[fliprayzin240sx]

Check the coilpack wiring, maybe the ground for that cylinder plug is bad.

[joelg4461]

I checked it with a test light and there is ground but I'll remove the harness and check it out.

I also intend on doing a leakdown test but I don't think it would be bad when I have compression at 140 in all 6.

[joelg4461]

I did a leakdown test and it was leaking less than 5% which is great. I checked the wiring harness back to the ignitor and it all checked out fine. I don't know what else to do at this point.

[baube]

is the coil getting hotter thant the others?

[S12 Drifter]

ignitor i would assume

[nyc240sx]

get a new coil pack harness from wiring specialties that fixed my problem

[budderigs]

my rb20 has bad exhaust valves and still runs fine with 80psi of compression on all 6.

my guess is no power or no ground going to the coil harness. I had a plug on my harness once that the pin was loose inside the plug and it would lose connection.

the igniter might be an issue as well but doubtful. igniter issues are normally random misfires on all coils.