Hi all,
I've recently had a misfire on my car (Saab 900 2.0) that turned out to be the coil gone bad (resistances were way out) and it's now fixed. However, I want to understand the underlying reasons, as I can't quite make the connections in my head.
The misfire was occasional at idle and light throttle at ~3000 rpm, and heavy for 1/2 sec when accellerating hard from low revs. All other driving was perfect.
I'm trying to understand the relationship between the changes in cylinder pressure, mixture and required ignition voltage that caused this, but it doesn't stack up for me. I understood that you needed the highest firing voltage with weak mixtures at high cylinder pressures. But the misfire occured mostly at idle (weak but low pressure). It was worst on hard acceleration (high pressure?, rich mixture) but fine at high RPM full throttle (rich, high pressure).
I've seen some info about ignition voltage sag with the throttle snap test, but no details.
Could someone explain any of this?
Cheers Jon