Afternoon folks. Car was running very smoothly, until it occasionally developed a flutter at partial throttle, noticeable once a week or so. Fast forward to a long highway trip, and the problem at part throttle becomes much worse, leading to dash lights and a complete (EML) shut down on the highway.

Curiously, it ran like this intermittently for the weekend. After sitting overnight, the lights (traction control) did not reappear and the car drove fine while babying it. Getting back on the highway caused the problem to reappear permanently.

At this point, it was still idling fine. I was able to continue to drive the car by avoiding half throttle— loping between coasting and mild acceleration. Made it back to Minnesota from Ohio like this(!)

Now, the car has trouble idling and will typically stall when coming to a stop without a throttle blip. Partial throttle is very rough, full throttle is OK but clearly down on power, and will cause the car to go in full shut-down mode, with EML light. Restarting clears the EML and allows the car to limp.

I have five P codes, two of which are 0000. The other three are:

P1106
P0107
P1688

Indicating MAP sensor faults. When the problem is occurring (traction control light on), Scangauge II gives a 0 reading for MAP and boost reading is frozen at a vacuum reading.

No obvious problems with wiring or corrosion on the ignition coil. I would delve deeper but I just moved and am hesitant to start disassembling the car, street-side.

The interwebs suggest MAP problem or crank pulley on the way out.

Additional diagnostics to try before I limp it to the mechanic?

'06 R53 with ~148k miles.

 

Look into the crank pulley failing as well as the possibility of the SC pulley slipping on the shaft, we've seen that on a couple of cars this year already.

MAP sensors aren't really a high failure item, but the MAP sensor on the intake manifold is prone to having the insulation rub through on the core support and cause corrosion and weird boost issues.

You could also be needing a bypass valve if the spring is either broken or the butterfly is sticking, give that a look as well.

 

And it was the downstream MAP sensor!

Thanks for playing folks!