Hi all,

I had my Cosworth YB powered Mk2 Escort up on the rollers yesterday to check fueling. Unfortunately, after the first run up she developed a missfire when under load (approx 3500 RPM).

A bit of background on the engine:

Freshly ran in 2wd YB
Freshly rebuilt T34 with 0.48 compressor housing and -31 actuator
803 Injectors
3 Bar MAP sensor
MSD chip to suit the above setup
New MSD leads
New plugs
New GPA coil (MSD)
New crank position sensor

When cold - it boosted well up through the rev range... however, when hot, it started to break down and missfire. I changed out the ignition amplifier and air temp sensor today as I had spares in the garage and they made no difference.

Any ideas what it might be??