GT40 engine miss at all RPM

[kend]

The miss started last year but is getting worse. 2001 GT40 fuel injected
Cranks right up when cold or hot, but has to turn a few seconds if just warm. It has just a slight miss at idle. When you give it gas the miss becomes more apparent but the RPM will still climb to over 4k and the boat will go 45mph. At 4k RPM you hear a quick blip every .75sec
The miss gets faster at high RPM but feels more time based than a bad cylinder
I replaced the spark plugs last year and looked at them this week, they all look even and clean. Cap & rotor are 2yrs old but look clean.
I'm planning on replacing the TFI module tonight (kind of just a guess)

Has anyone had this issue?

[gun-driver]

Check your exhaust manifold gaskets for a leak.

[kend]

Is the idea that it would drip water on the plugs?

[ESP]

Compression, plugs for cracks, wires, take a magnifying glass take a good look at the rotor for cracks in the cap, a couple ozs of sudsy ammonia in 8 oz of water and spray the wires if you have a wire shorting the spark will follow the ammonia like a lightning bolt. Not likely a module or coil, if it fires right up.

[kend]

a couple ozs of sudsy ammonia in 8 oz of water and spray the wires if you have a wire shorting the spark will follow the ammonia like a lightning bolt.

I've never heard of this but I have been wondering if the wires are ok; they have been replaced by previous owner with nice 8mm (except coil wire). Searching I found multimeter/ohm tests and a guy spraying just plain water in the dark....but ammonia...sounds dangerous. I'll try it tonight.

Also replacing coil wire and installing TFI module & lake testing today.

[charlesml3]

Replace the cap & rotor and all of the plug wires. It's a cheap test and probably something that needs to be done anyway.

This is an ignition problem almost for sure. Eliminate this first.

-Charles

[gun-driver]

Can you actually feel the miss in the performance or is it more of a sound?

[kend]

just a sound most of the time, but when you take off from idle you can feel it

[Jonny Quest]

If not the Thick Film Ignition module, then I would look at injectors…

JQ

[gun-driver]

just a sound most of the time, but when you take off from idle you can feel it

A leaking exhaust gasket can make a ticking sound like a miss, that’s why I suggested it earlier. I would rule that out before throwing more parts at it.
If you can really feel it then I would as suggested above check for a arcing spark plug wire then possibly replace the cap and rotor as they are cheap.
I would think it’s ignition more than a fuel delivery issue at this point.

The feel of a miss during acceleration from idle could be a drive line vibration from the prop or alignment.

[kend]

Just got back from lake test and it runs like new. I replaced the TFI and the coil to distributer wire...so not sure which did the trick. I'll keep the other plug wires, cap, rotor for a rainy day.

[gun-driver]

Glad she's running like a champ again
If you wanted to see which did it throw the old coil wire back on it, you may have a spare TFI also.