V6 popping and missing firing

I have a 156 that has a gas conversion. Whilst it warms up on petrol it miss-fires and pops, but when it goes over to gas it's fine. It also has the motor system falure notice up.

Yesterday I thought I'd try and give it a clear out on petrol on a bit of dual carrage way so switched it back to petrol, dropped it down couple of gears and floored it. It failed to pull at all and motor system falure notice repeatedly kept sounding for several seconds after I lifted my foot.

Is this possible symptoms of the air mass meter? I know it's nothing mechanical as it runs fine on gas.

Any help would be gratefully received,

Cheers, Rick.

When were the Spark plug changed last?

I must be honest I've had it for 18K and I haven't got a clue when they were done before that. I think I'm going to have to have a chat with my local indi specialist. I'd change them as a proccess of ellimination, but it's a major strip down especialy with all the gas plumbing too.

Cheers, Rick.

Its probably your air mass meter. Is it a single point injection system or multi point injection gas system?

Either way, I think LPG systems just use the lambda in a feedback loop and ignore mass meter readings.

I'm still going Sparkplugs i've had both MAF and Dead plugs on a V6 and a MAF wont cause popping and mis-fire, but dead sparkplugs might also the gas will more than likely tolerate poor spark.