Twood

Couple of questions:
Does the twin plug set up on a 964 fire both plugs at the same time?

Does it make any difference which coil lead goes to which distributor?

I am trying to diagnose a misfire that has happened to me twice now. For no real reason (eg hot engine) I suddenly develop a misfire, car will not idle, engine cuts out etc

If I change the lead from coil 1 to distributor 2 and vice versa the problem appears to go away.

I have changed coils and coil/distributor leads with new items about 12- 18 months ago and last week the problem came back- changed leads from coils to the distributor and problem seems to go away

PS Scan tool tells me I have a hall sensor fault but the general running of the car is fine (unless I have the misfire)

thanks in advance

Silvertarga

If you used the silver coils then change back to your old black ones, the silver coils are terrible

Both plugs fire at same time ,

Twood

They are the black ones- the coils in the car are made in Brazil, the older coils (probably original) are also black and Made in Spain.

Thanks, I thought they both fired together but other people put doubt in my mind

Alex Sol

the silver coils are know to crap out but can do a resistance (ohm) check on them. try unplugging the hall sensor (at the distributor) and see if there's any difference

Alex Sol

i'm checking the ignition control modules - well going to replace them - and see if it helps with my idle / driveability issues - they are $50-100 each depending on who makes em.

Alex Sol

from 911chips.com

The Porsche 964 and 993

Starting in 1989, with the twin plug motors of the 964 and 993, there are two spark plugs per cylinder which fire simultaneously for more complete combustion. Because the spark is fired from two locations across the cylinder head, the time to total fuel combustion is reduced, reducing the amount of ignition timing advance necessary to achieve the optimum peak pressure point of combustion after passing top dead center. Because of this, the amount of spark advance before TDC of twin plug motors for best power is typically 7-9 degrees less than that required for a single plug 911 motor.