Code P0302, engine miss?

Thank you for your reply, Ken. Your answer does not apply to my vehicle as it has a throttle body injection system with a distributor and old fashioned coil and spark plug wires. Is there a way to test for spark in the cylinder? Any other ideas why still missing? I suspect intake manifold gasket or head gasket but would like to troubleshoot to know exactly before unnecessarily taking engine apart.

New plug new wire and spark seems good when plug grounded to exhaust manifold. Is there a way to test the spark if the plug is screwed into the head? Thought maybe a short somewhere. Did 4 revs on compression gage and got 155psi so assume the valves and rings are ok, also removed valve cover and no stuck valve. I tried vacuum leak test with propane torch, but nothing will try again. Can intake gasket leak be determined from outside the manifold? How can I test the intake gasket and head gasket to determine if good?

I pulled all six plugs and the one from the dead cylinder looked pretty clean no rough tan appearance like the rest, like it was steam cleaned from a coolant leak into the cylinder. It was consuming a tiny amount of coolant, so I did a K seal head gasket sealant treatment. But the miss is still there. The coolant consumption is very small and have been adding alumaseal to the radiator every couple years to keep it at bay. Could I feed some clothesline into the spark plug hole and run or just turn over the engine to see if it gets wet and smells of gas or coolant or would this cause damage? I will do more propane leak testing when the wind dies down. Does placing hand over oil spout and feeling vacuum mean a possible intake gasket leak?

Update. Connected propane torch nozzle to pcv hose and ran propane into intake manifold. Still rough idle but check engine light did not come on over several minutes. Reconnected pcv valve and p 0302 came back. Will wait till engine cools to do more propane tests. Also, ran engine with radiator cap off till operating temp and no bubbles in coolant, so head is the gasket okay?

Also, would old/bad or water in gas cause a p0302 misfire code?

Update. Disconnected hose from pcv valve and engine idled rough but did not throw a code for 10 minutes. Reconnected the hose and threw a p0302 code in less than a minute. Could a bad pcv valve cause a code p0302?

I am getting a new PCV valve today. Put my hand over oil filler neck and didn't really feel any suction so maybe intake gasket, okay? I might try tightening TBI nuts also. Just curious why disconnecting the PCV hose gets rid of the check engine light and 0302 code.

Put in new pcv valve but still miss and 0302 code. For the head gasket I used Kseal and have no bubbles in the radiator or no milkshake on the dipstick. Did you mean the tbi gasket on the intake manifold or the orange gasket to the snorkel? The spark plug is a new iridium. I also spray cleaned the MAF sensor. Wonder if its just bad gas to throw a code 0302.

Yep, it has a nervous idle, you can feel the truck shake. I drizzled about 3/4 bottle of Seafoam down the throttle body let it soak then took it for a hard drive up to 75 mph. It seems to run good at high rpms but has the idle miss. I was thinking of pouring water down the carb like we did as teenagers. I will try to video but am not very good at it I am old.

Doesn't the all-cylinder compression test get the relative compression of all the cylinders to detect a weak but firing cylinder? I just tested the misfiring cylinder several times and it always came up to 155psi. Wouldn't that rule out the valves, rings and head gasket as faulty? Could any of those be faulty if the cylinder still compressed to 155? On the vacuum leaks I sprayed carb cleaner around and didn't hear any engine rpm increase. I'm starting to think intake manifold gasket, any ways to target that with a test? And is that a common problem on chevy small blocks with only 120k miles on them? I've had 350's run to 300k no problems, but those were older, built in the 70's.

Update: Yesterday I tried to pour water down the TBI, but I couldn't stop the engine from shutting off with the air cleaner snorkel removed, so I nixed that test.

I already removed the EGR valve and cleaned it with some WD40 spray, so it is not stuck and the valve springs freely. The EGR valve in the video looks different, mine doesn't have a dashpot. I will try to upload some pics of the engine this weekend if I can.

Update. Would a spider injector have a throttle body, a distributor, and one coil? I thought a spider injector had coil packs.