Missing down low

[Joes_meat]

A mate of mine has asked me to fix his Series 1 6-pot VN.

He says it's missing at low revs, he thinks it's missing on cylinder 5. He replaced leads, plugs, cleaned the TB, changed the oil.

I'm thinking it's coil-pack (it's the old S1 style) or the DFI module.

Is it possible to pull off my VS coil-pack and put it on the VN for testing purposes? Or is there a better way to test the coil-pack and DFI module?

In the case it's not the coil or DFI, what else could it be?

[AdamIan69]

My Vn does the same thing, i noticed it gets worse the hotter the engine gets until you can hardly accelerate in 5th gear. i have changed my leads, plugs, coils, DFI module, and MAP sensor. i took my VN for a drive tonight waited till it got to full operating temperature, and then pored 2 litres of water of the Crank Angle Sensor, to cool it down. it didnt completly stop the miss, but helped it considerably. give it a go and tell me how you went!

[anton1o]

I would strongly think its the Coil Pack..

[AdamIan69]

I have replaced them with S2 coil packs and dfi module, didnt work? Anything else it could be.

[Joes_meat]

Didn't test the coil-pack.

Did a compression test and cylinder 3 had 50psi dry and 80psi wet. Every other cylinder has a very even 125psi.

I'm thinking bent-valve, stuck valve seat or broken piston ring.