300xs cutting out

[Dave_r]

Hi Folks

i have a 300xs that some where around 6000 RPM on a flat out run the engine starts "missing".

Behaves like protection kicking in but no faults being recorded on my DDT. My filters and VST are all clean so we're pretty sure it's not a fuel supply issue.

Didn't some series of these engines have coil problems at higher RPM?

I can cruise all day below 5800 RPM.

I have a DBR and STOCk ecu, both do the same thing.

Thoughts ?

[Davidlake]

Man, You need to use spell check. Your post is intelligible! :confused:

[Dave_r]

Sorry, rushed on my phone. Hopefully better now!

[Davidlake]

Maybe a coil starting to go bad. Start by checking your spark plugs for a fouled one. If so likely a bad coil. Those coils are notorious for being bad. If fact, Mercury was replacing all of them if one was bad when the engine was under warranty.

[Wayne Cammidge]

Put a computer/ DDT on it and then run it till it starts missing and do a cylinder drop test.
Once you know which cylinder, then change good know parts to that cylinder.
One good part from each cylinder separately.
Then run it again and see where the problem has gone.
Will tell you very quickly where the issue is and what needs replacing

[Euroski]

Get your ohm meter and check the resistance of a 6 sparkplug wires. On my 300xs 2 were open circuit. Also I had 2 coil failures since 2007 and both coils produced NO SPARK

[Dave_r]

Thx folks will try