Hello, I have an audi a6 2.7t..car is shuddering at idle and under load..car is throwing p0102 MAF air, and a p300 cyl 2 misfire..checked all vac houses/connections everywhere..no leaks. The vac house Up by the drivers side diverted valve where it connects to the hard line by the throttle body is making an extremely loud hissing sound..(seems like it is overpressurized)there are no leaks however and the other dv side is quiet? What gives? Only thing I can think of is the drivers side turbo is seized up..

The other day it started shuddering under load, then suddenly smoothed out..only to have returned later

Any ideas guys?

 

If you have the stock diverter valves still, it might be time to replace them. If the diaphragm ruptured, that is where the hissing noise would be coming from

 

Hmm..I switched the valves around though. Still no difference..what about the n75 valve? That's the main diverter right? Still not exactly sure what that does..also cleaned throttle body..ran fuel system cleaner through..unplugged MAF and car still runs like crap, ruling that out.

I unplugged each coil pack at a time with the car running..noticed that on cyl 2 made no difference with coil pack off. Pulled and replaced the plug..bad injector or something else wrong with that cylinder?

 

Likely a bad coil - failures of coil packs are common. That would likely fix part of the issue.

 

Figured it out..it was a bad ignition control module..did the switch test and the dead cyl jumped over to the other bank of the motor