[Volkom]

Hi All,
2013 BMW X3 with the N20. ~81,000 miles on the chassis/trans. Engine is a 2017 N20 with ~55,000 miles with many accessory components on the engine, like the turbo, being original to the car. I replaced the engine myself after the timing chain broke a few years ago.

I need a way to diagnose what I suspect to be a bad diverter valve without just throwing parts at it.

I'm having a new and recent issue with:
120308 - Charge-air pressure control, plausibility pressure too low.

It comes up at highway speeds (75+mph) when I'm cruising along, i.e., i'm not pushing the car. If I stress test up to 60mph by hammering the car at WOT I have no issues at all. Even cruising (light driving) at lower speeds doesn't trigger it. The annoying part is that the problem is intermittent yet not random if that makes sense. It never happens at idle, for example. I don't see how this can possibly be related to speed since what gear I'm in shouldn't matter to the engine if I can simulate an equivalent load at a lower speed going up a hill.

DIY smoke test passed but i'll keep trying.
Plastic air intake pipe was replaced two years ago, no visible cracks seen now. Charge pipe from turbo outlet to intercooler has the o-ring, looks good but seems to temporarily collapse if WOT -> sudden dropoff in throttle, slightly expected.

Vacuum lines look good visually, they hold vacuum when tested with a handheld vacuum tester. No leaks to the line that runs to the exhaust flap.
No leaks in the vacuum line from the boost solenoid to the pneumatic wastegate diaphragm. When i test the VAC line (vacuum provided from the pump to the solenoid) it holds vacuum. When I test the OUT line (goes from the solenoid to the PWG) it doesn't hold any vacuum at all, but I'm not sure it's supposed to when the solenoid isn't triggered.

When I do the ISTA tests the PWG opens and closes as does the exhaust flap. I will say, though, that the PWG opening is smooth and potentially sluggish but I have no reference to compare to. The PWG closes at 7.5 in Hg but it's supposed to close at 6 in Hg. I don't feel like taking off the rattling cotter pin to adjust the PWG clearances yet unless you think it could be the issue.

My boost solenoid (TIS calls it a pressure converter) is one of the ones identified as needing replacement by part number, but my symptoms are not jerky throttle/engine speed variations so I'm hesitant to say this is it. 11T290 to 12T157 require replacement- mine is in that range.

ANYWAY- how do I diagnose the diverter valve without taking it off and hoping that's the problem? Is the GFB DV+ a replacement to a faulty stock DV or would I need an OEM DV and then the DV+ bolts onto it? I'm not really sure what the internal construction here is so the question may seem ridiculous. I assume I'd only need the DV+ if my OEM one in the car right now is faulty.

Or, do you think of any other causes?


I also had several issues that appear to have disappeared after I replaced components. I don't need input on these but they might be tangentially related somehow. I'm not sure how that would be possible, but who knows.

140102 - Misfire, cylinder 1
140002 - Misfire, several cylinders
140110- Combustion misfire, cylinder 1
140010- combustion misfires, several cylinders

Replaced cylinder 1 and 2 fuel injectors- I had a problem with swapping the EU5 injectors from my old engine to the new engine that had EU6 two years ago. The EU5 injectors took much much more force to remove than TIS specs. TIS says replace if the force is too high- I didn't and it ran okay but not spectacular. It's better now with new injectors- I'll do the other two soon, it's an easy job but I don't like to throw money at issues without knowing the cause.

1D2404 - Map thermostat, activation, line disconnection

Replaced thermostat, seems fixed

Thanks!

[E36M3]

Your likely sources of this you’ve already identified: boost solenoid or diverted valve. If you pull the diverter valve out your can partially disassemble it and inspect the rubber diaphragm and how smooth it’s operation is. Most likely it’s your boost solenoid. No real good way to independently check them.

[csdc20@gmail.com]

Hi, were you able to resolve the issue with your n20?