About 6 months ago i replaced my intake gasket to fix a coolant leak. Eng lite came on but started and ran fine. 3 or 4 months later it starts to misfire only when cold or wet outside. Once warmed up, it ran fine. Gradually got worse when wet outside but always started and ran, and got better as it warmed up. I replaced cap, rotor, wires, plugs from azone. No difference. It rained last week, went out to start truck, no start. Cranks and sounds to me like it's out of time. Have fuel at plugs. Fuel pressure is good. Have spark at plugs. Appears to spark at correct time, testing with finger in plug hole and looking at spark. close to 100 k on engine. So, i got fuel and spark, but not hitting at all. It does sound like it hits one time right after i stop cranking the starter.??? Lotz of similar post on here but it seems no one takes time post what it took to fix the problem. I'm probably overlooking the post that explains what i need to look for. I'm going to chk compression today to rule out the timing chain. Any suggestions? I don't have a scan tool.

 

How does it sound like the timing is off? 100K is pretty low to skip timing. Especially for a 350.

And how do you know you have spark?

I think your problem is electrical in nature. Did you check your PCM? Are the wire harnesses frayed? Is your PCM sending a signal to the ICM after you release the key? Does it have this issue with different keys in the ignition? PASSKEY issues can cause this problem=Start Inhibition.

You re going to need a Code tool to see if you get a response from the PCM and even if there is a CKP sensor or something that went to bed on you.

 

Compression does not change when it is wet outside.