my cosworth has developed a missfire for the first time under load at about 4000 rpm. so far have changed coil, cap, rotor arm, cps, phase sensor, ignition amp. checked & cleaned all connections & all the wiring multiplugs near the bulkhead have been removed & hard wired. only thing left are the leads which all appear ok but when I measured the resistance all were showing around 2ohms is this right?

 

Sounds a bit high m8 .

 

I'd be more concerned with Insulation resistance than resistance of the core itself. Don't know what the figures should read for leads, but lower the better, a quick google search seems to suggest ~3-5k ohms is right. You sure its 2 not 2k?

Low insulation resistance on the other hand would give misfire.

 

Check your plugs, don't no your engine spec, but if standard 1mm gap, if stage 3 reduce gap to around .6mm to overcome spark blow out.

 

plugs are denso irdium as specced by nms running 2bar only done about 1000 miles

 

Checked fuel supply then ?
tabetha

 

If you have checked all the ignition components.........

Is it exactly 4000 rpm ?

Try revving it gently on the spot.

If it is, it is most likely to be a sensor fault and the ECU is deliberately rev limiting the engine to protect it.

Does the rev counter operate correctly and smoothly when in the problem place.
If not, its the crank sensor...

 

sell it