Truth be told... my '06 R53 is pretty upset with me as is... my CEL's (At the moment) are..

P0128 - I have the M7 Thermostat and in the winter I need to let it warm up; but sometimes I don't have time, so this guy comes and goes.

P0456 & P0442 - EVAP System... I need to find the leak, but it's not something that really bothers me too much.

And then the problem... P1688 and P0107.

The usual suspects...

Crankshaft Pulley - I already replaced this when it failed last year with the ATI.
Belt - Replaced with the Crankshaft Pulley.
Tensioner - Replaced with the Belt.
Throttle Body - Replaced last year when I had similar problems... ended up being the crankshaft pulley.
BPV - Replaced last year with the Throttle Body, replaced by DT-BPV.

The symptoms have been either spikes or hesitation under part-throttle and off-boost situations... and have generally only popped up after a couple minutes of highway driving, like the issues never really happen on the surface streets.

I have the M7 16% Pulley, have had it on for over 100K miles. I'm wondering if that might be the culprit? I have seen images of the pulleys which featured similar designs fail.

What are the other things to consider? Lemme know, gents...

 

Seeing lots of complaints due to the BPV. Can't link this forum on here as it's blocked so I have pasted from it below. The hesitations could be related to possible leaks in the system as I did stumble upon a thread where boost issues were present for someone with codes P0171 and P1688. Code P1688 and hesitation went away once fixing:

But code P0171 came back and the solution was:

Another different solution for someone else.

Hope some of these help with your diagnosis and let me know what you find.

 

Do you have the correct size belt on the car for your setup?

Have you done any electrical diagnostic on the MAP sensors? MAP sensor issues will give you these lights and codes as well as the extensive list of other components you've replaced.

Our DT BPVs are all hand actuated to check the diaphragms, and all hold vacuum prior to being boxed, now that's not to say that over time the spring was able to puncture the diaphragm.

You can remove the vacuum source from the brass nipple on the BPV, squeeze the diaphragm, place your finger over the vacuum line and see if the diaphragm holds vacuum. When you release your finger from the line you should either hear an audible click as it returns to the set point or be able to see the diaphragm return to the set screw. If there is in fact a problem with the valve we will be more than happy to help you out in every way possible to get the car running again.

We will be the first to say that the DT valve may not be for everyone, as it does change how boost comes on and can feel jerky or lurchy to some people that feeling is normal for how the valve is designed. As for our valve causing CELs, that's hardly the case as we've sold thousands of them with no issue.

 

MAP Sensor - With the OBD-II reader hooked up it's giving me the proper atmospheric altitude, but I know that reading is just with the TMAP sensor and I know we have two of them.

BPV - I'll try to see what I can find in terms of operation. I'll put some vacuum on it and see if it holds.

Belt Size - I need to check my belt-size... I know it's a Continental Elite (Gatorback was bought by Continental) The box here in my toolbox is the 4060537 (6PK1365); if this is what's on there right now, then I think... I may need a smaller belt from what I can recall? I have a 16% Pulley. I'll double check in a few minutes.

6PK1365 Belt is 1365mm long, for reference. According to M7, their recommendations are a 1367mm belt.

 

I'm at Half-Circle with the belt tension... but honestly I have no frame of reference into what that means.

 

Half circle showing is fine, once you don't have any of the hole exposed is when I would recommend replacing the belt, or if it starts to deteriorate.

 

I still have my old BPV, it's holding vacuum well... I just did the DT-BPV because I thought my BPV was bad last time when it turned out my crank pulley failed. I can't touch anything until the weekend but I might swap back to my OE to see if that helps.

I'll try to see if I can test the DT-BPV first before digging too far into it.

 

I haven't had a chance to get to it because I've been working... literally every single day since my issues started.

I managed to get a small video of the boost spikes... they're not subtle at all... when they happen the thing kicks like a mule.

Does this seem like a BPV issue or a throttle-body wiring issue?

Have no idea why there are two videos up there... I tried to get this thing to post correctly to no avail.

 

I finally had some time to pop the hood in daylight... and I realized that I was looking at the tree, but not the forest.

The last thing I messed with was the ignition and fuel injectors because I had a bad post on my coil. I removed the intercooler and didn't put it back on right; additionally... my boots are just beat to hell.

So I started thinkin... well, that makes sense. If I have a boost leak then I wouldn't notice it under throttle with the exception that it would feel like a slight loss of power.

Under vacuum, it would cause the BPV to modulate incorrectly because now the BPV is fighting a leak in the system.

So I put some new IC boots on Will-Call and I'll pick them up tomorrow. Even if it's not the problem.. they're still beat up and need to be replaced; so it's a Win-Win and one less thing I gotta worry about.

 

I replaced the boots... and it's been a couple days now. I also figured... while I was at the dealership, pick up a new gas cap; apparently they changed the design so I got that.

So far... no check engine lights; but I know that the problem isn't completely gone. I still feel flat-spots of hesitation at part-throttle. So that kinda sucks because I know something is still wrong...

And then of course... something else is now broken because... why wouldn't it be?

Now it sounds like a diesel at idle and it's not going away through the RPM range. I've been reading around that's it's probably my timing-chain tensioner; but I just replaced that like two months ago and it was completely seized.