Been reading other posts and made a few too about this but I have a bit more info.

97 UK turbo 2000 with Apexi ECU.

Im getting an occasional misfire and it seems to happen more after I've put my foot down a little - it doesn't take much though, I have to be really gentle on the throttle.

I've check the plugs, swapped out plug leads and coil albeit for 2nd hand ones. Plugs VERY sooty when I first checked, I know this can be indicative of a misfire but it could also be a symptom of dodgy lambda and ECU making mixture too rich - hence misfire.

Oh - all plugs were same colour so it's not a single plug lead.

I've been looking at the voltage output of lambda on the Apexi controller. Normally it cycles from 0 - 0.76V on cruse and tick over when warm. 0V on over run and a steady 0.88v ish with wide open throttle.

When it starts misfiring the voltage reads a steady 0.88 or 0.9V even when on light throttle. It seems to clear the misfire when the lambda sensor starts to cycle up & down again.

Anyone know if this is indicative of a knackered lambda sensor or is the sensor just reporting on the state of the exhaust while something else is causing the misfire?

This seemed to start a while ago when I changed the plugs and leads. Standard plugs, after market leads (present). I was a doofus as I didn't fit one of the leads properly and it fell off the plug, I so I have a quite a few miles on 3 cylinders, with the fuel obviously washing through the exhaust to the lambda sensor - could this have damaged it?

Thanks in advance