Turbo mx5 misfiring under boost

[Mx5markey]

I have a mk1 1.8 turbo mx5, but this problem can relate to all turbo cars.

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.

[martycturbo]

Could be blowing out your spark alright,, worth gapping them down a bit,,

[Mx5markey]

Cheers, I'll give that a go as soon as I get my hands on a gauge. Any idea on gap size?

[Ptank]

Check the air flow sensor too.

[martycturbo]

Cheers, I'll give that a go as soon as I get my hands on a gauge. Any idea on gap size?

Measure them all and go a few thou down on each, just make sure they are all the same starting off,, trial and error will sort it