912is rpm drop

I have seen the 912iS sensors read hot when they are beginning to fail.  So while unlikely, it’s possible your EGT readings are not associated with the RPM drop you are seeing when checking Lane-A.  Replacing coil SP1 as discussed earlier is a good step, but if that does not fix it then you are going to have to go back to standard troubleshooting.  Also, from my observations 700 hours is just about the lifespan of the 912iS EGT sensors.

Check all the spark plugs, check that the plug boots are screwed on the wires tightly. Check all wiring and connectors to ALL coils and Injectors. Section 74-20-00 of the MMH has the ignition system inspection procedures, and specific tests for the coils are in section 76-70-00.   Check all the fuses in the Rotax fuse box, each injector is fused as is each coil.  Check the MAP and MAT sensor connections, each lane has its own set.  

I’m really surprised that you have a 1500 RPM drop on Lane-A and you are not seeing any faults on BUDS or a Lane fault warning light.  Hopefully others will offer some suggestions about what could cause this without a lane fault. Please let us know the outcome.  

update:

last night I replaced coil SP1 and engine started and performed a runup. no lane lights, seemed to run fine but I had to leave.

went back this morning to try again, started up real rough but kind of smoothed out. this time I got a Lane A light so i went and hooked up my computer. attached is the screen shots of the faults. looks like ignition on cylinders 1/2 as expected.

I have replaced all spark plugs, cut all the spark plug wires and re installed the boots, unplugged the leads to the coils and checked them for corrosion and tightness. 

checked all fuses in the fuse box.

if I Shut down lane B, the engine barely runs.

is there any way to verify that the ECU is sending power to the coil?

Marty

Hi!
Glad I just found this thread. We are troubleshooting the exact same error on our 912iS. 
We have also replaced a coil, all spark plugs and checked all spark plugs connectors.

A step we have discussed is to hook an oscilloscope to the input side of the coil to see of there is a signal going into it. Haven't gotten around to do it yet though. Could that be an idea? 

Marty,

I believe a wire or connector problem is much more likely than an ECU problem. Yes, you could put a scope on the coil pack and watch the signal, but I would do some more investigation first.  I know you checked fuse F7, which supplies 12+ power to coil SP1, and you have replaced that coil and checked the wiring to it.  Next I would check Connector X1 at the Rotax fuse box, specifically pin 15, which is the output from fuse F7 to the coil pack SP1.  Unplug the connector and look for discoloration on the pin and socket. You can use an electronics cleaner and then a dielectric grease on these connectors, but if you find a discolored socket it should be replaced.  

If the X1 connector looks good and cleaning and resetting it does not fix the problem, then I would then move to the connectors at the ECU. You can only disconnect and reconnect the ECU connectors 20 times, and you should log each time you do it.  Specifically, I would unplug and inspect the A1 connector at the ECU, and pay special attention to pin L2, which supplies the signal to coil pack SP1. With these connectors Rotax recommends using Deoxit D5 to clean and lube them.  Do not use dielectric grease on these connectors.   

Jeff,

 I will investigate those connections next. I agree with your suspicion that the issue is in this area. 

Thanks,

Marty