Intermittant rough running caught on VCDS

Every now and again my 05 will run very rough, almost like it's missing. I was out checking my torsion value today and the car started acting up. I scanned through the different channels and found channel 3 to be of interest. Here is a screen shot of the graph





I then took a log and brought the RPMs up incrementally until things seemed to smooth out. I'm not sure how to upload that so it makes sense but the car smoothed out around 1600 RPM and then when I brought it back to idle it was running smooth again.

These are the 3 codes I get regularly:

17057 - Cylinder 3 Glow Plug Circuit (Q12)
16485 - Mass Air Flow Sensor (G70)
16683 - Boost Pressure Regulation

I've only owned the car 3000 kms (2500 miles) and it didn't come with any maintenance history. So far I've replaced the intercooler hose right off the turbo and the one right before the "throttle body" plus all my fluids and filters. Car has 460k kms (285k mi).

I haven't had time to do a lot of other things on this car yet.

It's averaging 6.9l/100 (34.3 USMPG) which I think is bad (but it's a lot better than the van it replaced)

I'm not sure where to go from here so I would appreciate some input.

Any ideas of where I should start the troubleshooting process?

Start by looking up the codes at Ross-rech's wiki. Here, I did the first one for you http://wiki.ross-tech.com/wiki/index.php/16683/P0299/000665

Thank you, I don't really think any of the codes are related based on what I've read on the forums (but I'm happy to be wrong about that).



Looking at the graph I posted, MAF requested and MAF actual follow each other quite well so I don't think I have an issue there. A boost leak isn't going to cause my engine to run rough like this that I can think of and it's definitely not a glow plug problem.



I think from what OilHammer has posted in other places, the MAF and Boost codes are likely the result of a boost leak that I have yet to locate.



Could this be a fuel supply issue or an injector acting up? I haven't checked my cam yet but I don't think that would result in intermittent rough running.

You might check the MAF sensor/circuit. The16485 code is for an implausible MAF value.

A PD with an intermittent miss that doesn't record misfire CEL could be injector harness. You can tighten the connections to the injectors without replacing the harness. Look up CoolAirVW's youtube video on it.

https://www.youtube.com/watch?v=1WB-ygxOLk4

Replacing your fuel filter could be a good low-investment starting point considering there's no maintenance history. One of my Passats did nearly the same thing the other day, though it was right on startup. Seems to have been a one-off event. I had recently replaced the fuel filter, maybe some air just now found its way out of the filter.