First thing is a compression test. It's always good to know, takes minimal time, and let's you know the mechanicals are in good working order. Wish I had a buck for every tune up done on tired engines.
Pop plug wires one at a time with motor running . That will usually tell you which cylinder. May want to use rubber handled pliers. Listen to your motor, if you pull one that's firing you'll hear the change. When you pull a dead one they'll be no change.
X2 on pulling the plug wires. Be sure to pull the wire off at the distributor end. Ditto on a compression check. Another trick is to start the engine cold, lick your finger and touch each exhaust pipe as it warms up. If that cylinder is firing it will boil the spit under your finger, producing a "TSSsss" sizzle. Dead cyl = no TSSsss. SPARK - FUEL - COMPRESSION. Those are still the things you need to make it go boom.
Start it up at night in the darkest location you can find. With it running, pop the hood and look for any arcing. The cheapest and easiest test you can perform.
Rather than pull wires so you can shock the **** out of yourself put a short piece of 7/32 vacuum hose between the plug wire and the distributor cap for all cylinders and then use a 12v test light hooked to ground and touch the vacuum hose with the probe end to short out the cylinder.
I'd agree with doing a proper compression test to know that the compression is even and you aren't hunting through the rest of the systems to search for the elusive miss. Pulling each plug wire off while the engine is running should tell you what cylinder is the problem cylinder be it valve, plug, wire, cap or distributor issue though. Don't pull the wires off by hand as it can and will shock the **** out of you and if the engine has an HEI it will knock you on your *** if you aren't careful. Pliers designed to pull plug wires while the engine is running are pretty inexpensive in the tool section at the parts houses.
Sounds like the problem I had a few years ago. Finally gave up and took it to a shop with good electronic diagnostic equipment. It turned out to be the coil. Charlie Stephens
Post a video or picture. Last I knew vacuum hose was a pretty poor conductor of electricity. Sounds like a lot more trouble that just pulling wires to me
Vacuum hose has enough carbon in it to conduct, I first learnded of this over 30 years ago at a gm training center cl***. My favorite way to short cylinders is to hook up the ground lead of a test light to ground and carefully slide the probe between the boot and the plug wire till you touch the metal terminal and kill the cylinder. Another helpful way to find bad plug wires is to fill an old spray bottle with water and lightly mist the wires and boots listening for arcing.
There is quite a bit of carbon in vacuum hose, cheaper than a spark tester. Been doing it for 30 years when GM went to DIS ignitions. Try it for yourself if you don't believe it.
Wait til dark and fire it up in the dark, then look under the hood for sparks. Also something to think about is cross firing, if your plug wires are oil soaked they will cross fire or bleed as one mechanic told me once. I once bought an impala cheap because it had a miss until it got revved up. I saw that the wired were coated with oil and dirt so I changed them and it cured it.
this would be my first thought also. very common. tighten all the intake/exhaust bolts up starting in the middle. might stop it temporarily
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