912is rpm drop

Marty and Fredrik

Before you both make the 7 hour drive, I thought of one more thing that’s easy to check. Connect your BUDS computer and start the engine. Go to the Fuel and Ignition tab in BUDS and compare the values between Lane A and B for both fuel and ignition parameters. I’m not sure they should be exactly the same, but look for an obvious anomaly. Usually a MAP or MAT sensor fault will report an error, but just thinking out loud, maybe a sensor could be misreporting without causing a fault.  It would also be interesting to do a lane check watching this screen.  And if you don’t have the securing clips on your MAP and MAT sensors you should check those connectors.  

Thanks Jeff, we will give this a try before starting to take it apart.
We will record the screen while we test so we can upload it here after!

Good luck Fredrick.  I’m always interested in learning what can cause this type of obvious engine problem but will not generate a fault code.  There are probably a few folks around who know the most common reasons this can happen, but that information seems hard to come by. I would like to see an advanced troubleshooting class for these injected engines, where ALL codes are explained, and non-code failures are discussed.  

Did a new day of diagnostics today - here is what we found/learned.

The fault is on Lane B. Lane B controls coils 2 and 4. Coils 2 and 4 control all top spark plugs.

Disconnecting the two front top spark plugs makes the engine stop immediately when Lane A is turned off. 

We figured this means the fault is on Coil 4, supplying the two back top spark plugs.

We switched coils 2 and 4. No change.
We switched spark plugs on the front and back cylinders. No change. (all spark plugs are brand new)
We switched the spark plug connector cap on the front and back. No change.

We then connected a small oscilloscope to the input side of both coil 2 and coil 4. The signal going into the coils seems identical on both.

From all this we figure the ignition system seems to be ok?
Will go back to the airport tomorrow and have another good look on the fuel injection system.
We will also connect the BUDS system and look for obvious anomalies. 

We had a look at the injectors today and fuelsystem today.
We swapped the positions of the Lane A and Lane B injectors, hoping the fault would move to Lane A. It didn´t.

Measured continuity to all injector connectors to the fuse-box and checked all fuses. All good.

Running out of ideas again, anything we have missed?

Some photos and videos from testing is shared here: https://photos.app.goo.gl/NTQPqHjRP4DWPjoL8