MX5Ireland

The car is misfiring when I get to about 0.5 bar. A bad misfire, much like hitting a spark cut limiter. This happened after sitting for a week or 2, changed the leads. Drives fine off boost e.g. cruising. The plugs were the recommended ngk r copper plugs, only 1 or 2K km on them, if even that.

I put new plugs in (standard, not the recommended ngk r ones) and I THINK it improved ever so slightly. Think they need gaping, or just new ngk r copper plugs?

Before this, it was running great (bar a vacuum leak which is now fixed). I think, that the vacuum leak which cause the car to run crap and rich, may have wrecked the plugs.

what plug gap are you using? You also need a colder grade than standard.

yep, regap them down, sounds like the boost is blowing out the spark.

Got it, lads. It was the map, over fuelling.