E34 miss fire - BMW Forum

98shaikh · 10-30-2005, 05:54 PM

Hi

I have a 1990 e34 m20 engine. It seems to missfire occasionally but it only seems to do it when the engine is under strain, for example when accelerating hard or when for example you switch into 5th at about 30mph and floor it. It's hard to describe but its like some of the cylinders suddenly are not even fireing and then suddenly they will fire again. any ideas on what it is. Have checked the fuel filter and vaulve clearance. the distributor cap looks a bit old but could this be the problem. if so why does it only do it when the engine is under strain.

Please help

Cheers

Torque · 10-30-2005, 06:43 PM

I'd start by replacing the spark plugs because it may be that they are the wrong ones (incorrect heat range) or simply too old. And don't bother wasting your money on Platinum +2, +4, + anything. m20 doesn't like anything other than just normal, traditional spark plug.

btw. Are you sure your car is not chipped and you're running octane which is too low for it ?

98shaikh · 10-31-2005, 07:52 AM

What do you mean by chipped?? It didn't used to do this it has only started recently. Using same petrol as always. Do you think it could be something as simple as spark plugs. I will give it a go. What model are the standard plugs.

cheers for the help

Torque · 10-31-2005, 10:32 AM

Ah never mind about the chip thing. I thought you just purchased the car. There are performance chips out there, which require the highest octane petrol and if you use too low of an octane they can do similar thing. Since yours obviously doesn't have a problem with that, disregard it.

I am using just regular Bosch plugs.