Theweezersdad

I just picked up my ‘16 GTS from the powder coater (wheels) and of course, had a tire pressure message. No problem, I’ll drive it a bit and they will reset themselves. (They all showed okay pressure.)
While driving, I noticed the boost gauge was acting funny (full boost showing most of the time regardless of throttle position). I got up on the freeway and it just feels dead. It will pull pretty good, but nowhere near how it felt a month ago.
So, I think maybe the pressure message was telling the engine to not get too crazy.
Go off the freeway and the TP message turned itself off. I parked the car for a few minutes to see if that would bring life back. Nope.
Still sluggish and the boost gage is still goofy. The boost bar is orange (was it always, and I’m just now seeing it - I thought it was red).

I parked it again for about 30 minutes and took it back out. Same deal. When I got home this time, I popped the hood to check for any obvious loose hoses, connectors, clamps. Nothing. However, the ECU was humming/buzzing - I’ve not noticed that before.
I went back a few minutes later and the buzzing had stopped.

realien

Run a diagnostic tool, see if there are any pending codes, you can use a videntlink i400, ICarSoft MBii, most of the autel scanners or go to a shop that can scan. Usually if the car is behaving that badly you'd get a pending code, or a check engine light.

Orcbolg

Sounds like potentially a stuck exhaust valve issue.

https://mbworld.org/forums/w213-amg/...ost-power.html

https://mbworld.org/forums/w213-amg/...lve-issue.html

https://mbworld.org/forums/coupe-roa...lap-codes.html

JMalanox

^this. I had boost cut issues on my gts. On boost gauge, it would cut out/limp mode whenever I accelerated. OP, do you have rattling in your exhaust? I had light feathering /rattling in my exhaust when I let off the gas. Bought my gts at 7k miles, issue happened at 12k. I was out of warranty and MB wouldn’t compromise, so I opted for downpipes and have an exhaust in the making. If it’s an exhaust valve issue, best fix (and most economical, as MB quoted $6500 for oem exhaust) is a quality aftermarket exhaust. It will get stuck again down the road so oem is pointless. You’ll also get more smiles per gallon with aftermarket exhaust and DP.

Theweezersdad

I have noticed any rattling, but I'll certainly check. Now that you guys mention this issue, I did put my hand in front of the exhaust yesterday after I got home (I'm not really sure why - a habit from waiting for motorcycles to warm up I guess). Thinking back, maybe one side did feel different than the other.

Theweezersdad

I will. I have a friend who is lead mechanic at local Infinity shop. I'll ask if their scanners can give me a place to look. I just hate going into dealers blind, but this forum group is giving me great info on where to start!

Seems like stuck exhaust valve or low voltage after having car sit at detailers are the most common.

You guys are awesome!!!

Orcbolg

Another potential culprit:

https://mbworld.org/forums/coupe-roa...-no-boost.html

Theweezersdad

Just to follow up...
Scan showed three ECU and two TCU issues. Most likely caused by low voltage while it was at detailer. Cleared the codes, and she's back to normal.

realien

Ha. nice! always good to have a simple solution