As above.

I suspect that the MAF code is a consequence of the fault/red herring. I have scoped the MAF along with the ignition and injection and found no glitches that would correspond with the fault occurring.

I am aware of the TSB on this re the idle speed valve. I am pretty sure that this isn't it!

After having 'scoped the injection and ignition I conclude that what is happening is that, every now and again, the injection duration momentarily shoots up to 15-20 mS flooding the engine. Sometimes the ecu can compensate with the idle speed motor (with the result that the engine stumbles, then surges before settling back to an idle) sometimes it cant in which case the engine stalls.

I am minded to change the temp sensor on the grounds that it isn't expensive and that a glitch on it could cause this problem.

Any other suggestions gratefully received