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Rudolph · 03-03-2022, 04:18 AM

I have a 42 Mercury with a pertronic points replacement and new leads and NGK plugs, runs really well but after a long drive the other day it developed a misfire at idol like someone is switching the ignition off and back on, if i am in gear and let the the clutch out till the engine get some load and then push the clutch to the floor seems to trigger it, it dose not miss a beat under throttle,

I did notice one of the plugs has a burn mark down the side of the insulator on the outside, I tried a different cap and rotor, I gave the pilot mixture screws a twiddle,

I was wondering if my vacuum brake on the dizzy witch doesn't seem to work was sometimes letting the ignition retard then advancing ?

03-03-2022, 04:18 AM	#1
Rudolph Senior Member Join Date: Aug 2014 Location: North island Newzealand. Posts: 273	Misfire at idol I have a 42 Mercury with a pertronic points replacement and new leads and NGK plugs, runs really well but after a long drive the other day it developed a misfire at idol like someone is switching the ignition off and back on, if i am in gear and let the the clutch out till the engine get some load and then push the clutch to the floor seems to trigger it, it dose not miss a beat under throttle, I did notice one of the plugs has a burn mark down the side of the insulator on the outside, I tried a different cap and rotor, I gave the pilot mixture screws a twiddle, I was wondering if my vacuum brake on the dizzy witch doesn't seem to work was sometimes letting the ignition retard then advancing ?