V8 Misfire when wet ... probably

[dumbfunk]

Can anyone help me with a mystery intermittent problem?

My Griff500 has 59k miles and usually runs beautifully; it pulled over 300bhp on a rolling road recently so I believe the engine to be in good internal order. It did however break down in the pouring rain on the way back from Le Mans with a horrific misfire that made the engine undriveable. I fixed this with a new fuel pressure regulator but the misfire slowly began to come back.

So, I sent it off for an early 12k service with a specialist I absolutely trust, and driving the car home it ran perfectly until it really started to rain whereupon the same problem returned and I only just made it home. Yesterday with the weather dry, I basically wobbled and checked the leads on the coil, all of which seemed fairly tight anyway, and it now runs perfectly again.

As I'm about to head off for a 2500 mile lap of Europe does anybody have any ideas on this? I don't know if the rain thing is a red herring but all the usual electrical stuff was replaced at service. All I can think of was whether anyone has had a failing king lead (1 year old Magnecor that looks fine), corroded 100A fuse (no other electrical issues evident), dodgy fuel pump (starts fine always) or duff coil (replaced 6k ago - no idea of brand) and if these symptoms sound familiar? What have I missed?


Thanks lots



dumbfunk


(I put this in "general" as it might apply to multiple models)

[rev-erend]

I would check the spark is good..

[dumbfunk]

It's certainly good now - feels like a rocket ship!

[rev-erend]

So - is it fixed ?

[dumbfunk]

Sorry if I wasn't clear - it is fixed ... but not by anything I have done!
My fear is that unless I can find what it intermittently failing then it might suddenly un-fix itself in an rain soaked Austrian service station

Cheers

df

[rev-erend]

If it always happens when it rains - then I would suspect the leads (even magnicors..) as arcing occurs much easier in a wet atmosphere..

You can generally see this in the dark if it's wet..

Hope you find the problem before you go.

[Barkychoc]

I had this problem a long time ago (not TVR) and eventually found it by running the engine in the dark and spraying the engine bay (leads, coil etc) with one of those hand held garden sprayers, I sprayed a fine mist and you could easily see the spark tracking to earth on the coil.

Just be careful not to get tangled up with the engine if its very dark !

Chris