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Underboost code, but is it really a bad water pump??

5K views 3 replies 3 participants last post by  JustJamesTX 
#1 ·
Greetings,

On my 2016 M274 Metris, I get a generic underboost code under hard acceleration. The issue is worst in Comfort mode and if I hit the accelerator in Eco, it switches to Comfort and then goes into limp mode, revs go to 6k with no power before eventually kicking back down and power is restored. Limp mode is never "permanent" so to speak.

46k mi on the odo.

The condition seems to only occur when the engine is at operating temp, which leads me to believe the problem is like that described here in the C300 forum.

Pipes and fittings have been inspected (no cracks), but a comprehensive vacuum check remains to be performed. Turbo works great when engine is still warming up and under less than full acceleration. With the relatively low miles, I have little reason to suspect a faulty waste gate. I also need to pull the temp from OBD but the dash says the coolant is at 90-95c, which seems a tad high.

Other owners have linked this issue to the shoddy 722.9 G tronic conductor plates, while others still said it was a deteriorating catalyst.

Appreciate your thoughts!
 
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#3 ·
Greetings,

On my 2016 M274 Metris, I get a generic underboost code under hard acceleration. The issue is worst in Comfort mode and if I hit the accelerator in Eco, it switches to Comfort and then goes into limp mode, revs go to 6k with no power before eventually kicking back down and power is restored. Limp mode is never "permanent" so to speak.

46k mi on the odo.

The condition seems to only occur when the engine is at operating temp, which leads me to believe the problem is like that described here in the C300 forum.

Pipes and fittings have been inspected (no cracks), but a comprehensive vacuum check remains to be performed. Turbo works great when engine is still warming up and under less than full acceleration. With the relatively low miles, I have little reason to suspect a faulty waste gate. I also need to pull the temp from OBD but the dash says the coolant is at 90-95c, which seems a tad high.

Other owners have linked this issue to the shoddy 722.9 G tronic conductor plates, while others still said it was a deteriorating catalyst.

Appreciate your thoughts!
Hello just curious if you ever found the problem. my 2017 metris with 200000 plus miles is doing the same. I notice my wastegate linkage has a lot of play where the vacuum actuator connects.
to me only means boost leakage since is not closing all the way. your feedback will be greatly appreciated.
 
#4 ·
Same issue still ongoing for me after replacing the turbo, O2 sensors, boost solenoid, air temp sensor, boost sensor, and water pump. Considering things like vacuum pump and wiring harness now. Love my van but at times it's unsafe and undriveable if I can't go above 30mph.
 
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