Need engine misfiring advice Options

[oakdalecurtis]

Here’s a question for the braintrust.
I have a 1974 stock FI original motor, 130,000 miles. It has a Crane Fireball ignition and Novolny plug wires. It has always run flawlessly from startup. Lately, upon cold start, it has been badly and randomly “missing” for the first 2 minutes, especially on acceleration. It is not a constant steady miss on one cylinder. I can’t say that is isn’t one cyclinder doing the missfiring, but the miss is random, 2 seconds, 4 seconds, 3 seconds apart. Then it runs flawlessly after the first 2 minutes.. The AAR valve works fine. The MAPS board has been replaced with a new one a while back. I have checked that all the plug and coil wires are tight. I thought maybe some long term water concensation in the gas tank might settle and cause an issue. I added a fuel additive to prevent that, made no difference.
What do these clues indicate on where to start looking for the this inital start random misfiriing?

[VaccaRabite]

Yes.

Think about it this way. Something is happening that is keeping a plug from firing until the engine gets warm. So a great first step is looking at plugs. Make sure you know what plug comes out of what cylinder.

While you have the plugs out anyway, do a compression test. (engine cold, since you want to replicate the issue you are having with a cold engine - though if you get a dodgy result, do it engine warm too.)

And since you already have plugs out ant the engine is cold, do a valve adjustment. Hopefully you find everything more or less to spec. But if you find something badly out of adjustment it could be an issue you are able to nip in the bud before it becomes larger.

Since its missing badly, one of these tests is likely going to show you something what goes away as the engine comes to temp.

Zach