Misfire "A" Ignition
in 912 / 914 Technical Questions
5 years ago
I have an early RV-12 with 912ULS now with 450TT. Carbs are synched beautifully with electronic CarbMate. Synch is good at idle and just off-idle. L&R EGT’s are very closely matched from idle to WOT.
Problem…. Most of the time the engine runs smooth 1800 – 3000 RPM. Sometimes the engine has a miss at this low speed when “B” ignition is turned off. So, problem is definitely with “A” ignition. I have changed sparkplug caps to NGK Spark Plug Resistor Cover - 90deg. Elbow Type (LB05F) 8051 and installed new NGK DCPR8E Spark Plugs gapped to 0.025”. I thought maybe problem is temperature or moisture related but that doesn’t seem to be the case. The misfire almost seems like induction/cross-talk between the high-tension wires. Engine always runs smooth at 4000 + RPM and extremely smooth at 5500 RPM cruise. Either ignition can be shut off at cruise RPM and engine continues to run smooth.
Possible next steps:
Can ignition wires be replaced on 912 without buying new coils?
Maybe there is problem with magnetic timing sensor?
Maybe timing sensor gap is incorrect?
Any suggestions appreciated. Thanks in advance…
Problem…. Most of the time the engine runs smooth 1800 – 3000 RPM. Sometimes the engine has a miss at this low speed when “B” ignition is turned off. So, problem is definitely with “A” ignition. I have changed sparkplug caps to NGK Spark Plug Resistor Cover - 90deg. Elbow Type (LB05F) 8051 and installed new NGK DCPR8E Spark Plugs gapped to 0.025”. I thought maybe problem is temperature or moisture related but that doesn’t seem to be the case. The misfire almost seems like induction/cross-talk between the high-tension wires. Engine always runs smooth at 4000 + RPM and extremely smooth at 5500 RPM cruise. Either ignition can be shut off at cruise RPM and engine continues to run smooth.
Possible next steps:
Can ignition wires be replaced on 912 without buying new coils?
Maybe there is problem with magnetic timing sensor?
Maybe timing sensor gap is incorrect?
Any suggestions appreciated. Thanks in advance…
