Black spark plugs

[zed4]

I'm trying to get to the bottom of a small misfire in my TVR. It occurs around 1500 to 2000 RPM, it's only very small, but I notice it. It's also taking a long time to start.

I've removed the plugs today (so far only 4) and they're pretty black. What do you think? Are they too black, or is this normal on the RV8? I'm wondering if they're over oiled. I've got a compression tester, but it's the type you hold in the spark plug hole, so I can't do it when the engine is hot. I'll burn my hand!

DSC_6776 by danyeates, on Flickr

DSC_6778 by danyeates, on Flickr

DSC_6779 by danyeates, on Flickr

DSC_6780 by danyeates, on Flickr

DSC_6781 by danyeates, on Flickr

[zed4]

Just done a compression test on the offside, they were all between 190 and 200 PSI which seems nice and high, although it's hard to get an accurate result with that tester and trying to turn the ignition key on my own! can't do the nearside, can't reach the key!!

[zed4]

yknot said:

Hi Dan, my plugs used to look like yours until I changed the 7's for 6's. Unless you are regularly driving hard then the standard heat range that TVR used will soot up. Lots of discussion on here if you search.
Can't say it will sort your slight misfire as it could be many things, but mine had that symptom until I changed the TPS!!
HTH
P

Thanks. TPS = throttle position sensor?

[zed4]

Just tested the TPS, was at 0.29v and was linear up the range. I've adjusted it so that it's now 0.33 volts at idle.