Hello all,

2016 e63s with 85k ish miles. Have owned it for a little over 6 months. Recently developed an odd issue I'm trying to pinpoint. After driving a couple miles the vehicle starts to shake violently and cel flashes. Pull over, cut it off and back on again and it's back to normal. The first time it had no codes. Second time I got a bunch of misfire codes, P0505 and P0721. Thinking that the P0505 is the primary issue to chase.

The misfires are not present while idling or when driving before of after these incidents. I had my scan tool with me the second time to verify that with misfire data. Additionally it's for both banks. Codes for cyl 3,5,6, and 8.

The output shaft speed I'm guessing is because of how violently it's shaking when it's misfiring.

I did check the wiring harness and no oil is present in the connectors. Everything else seems fine. Nothing obvious from just looking it over.

So that leaves me chasing the P0505. Do these cars even have an iac valve? Where is it located? All I have is google and a scan tool until monday, so any help is appreciated!

 

Can you list your codes description in english so we can all be on the same page

-- You have a recent purchase that's misfiring violently on both banks under load with misc faults.

-- Everything resume normally after a simple engine restart.

-- CPS were proven dry

-- Occurrences :
- the first time had no stored codes !!
- the second time codes were recorded

(there's no IAC: throttle is in charge of 100% air)

> This matches your inputs well:
-- Go ahead and setup your IC Display to show "shop menu data"... battery voltage!
-- See if chassis voltage drops below 12.3V at anytime or under acceleration.

> Sudden + Random...
I don't think this has anything to do with fuel delivery nor ignition qualities.

> ECU is freaking out !
-- Disconnect batteries and check for oil at the ECU Connectors both sides.

++++ PARTNERS:
ECU directly relies on CAN partners data... ESP, TCU, CGW.
Pay attention to All Modules for their ability to snowball what you're reporting.
Meaning don't only concentrate on ECU alone.

 

I would strongly recommend 8 new spark plugs and 8 new Bosch ignition coils.

 

Is this car modded - ecu or intakes?

 

I’m with jaybird, how old are the plugs and coils

 

Your original post entered in chatgpt

You’re on the right track by focusing on P0505 (Idle Air Control System Malfunction) since that could contribute to the misfires and overall rough running. However, there are a few things to consider before zeroing in on an IAC valve, as modern Mercedes-AMG engines (like the M157 in your E63S) use electronic throttle control instead of a traditional IAC valve.



Breakdown of Your Symptoms and Codes:

1. Misfire Codes (Multiple Cylinders, Both Banks - Cyl 3, 5, 6, 8)

• The fact that misfires appear suddenly, violently shake the car, then disappear on restart suggests something electrical or control-related rather than a mechanical failure.

• Given that it affects both banks, a shared system (fuel, air, or ignition control) is more likely than isolated components (e.g., individual coils or injectors).

2. P0505 - Idle Air Control System Malfunction

• The M157 engine doesn’t have a separate IAC valve; idle control is handled by the electronic throttle body.

• This code could indicate a problem with throttle body operation, adaptation values, or even a vacuum leak affecting airflow at idle.

3. P0721 - Output Shaft Speed Sensor Range/Performance

• Likely a secondary code caused by the violent shaking/misfiring, which can cause erratic sensor readings.

• If the transmission was struggling to get proper speed input, it might have contributed to the issue (but not the root cause).

Potential Causes & What to Check:



1. Throttle Body / Electronic Throttle Control

• Given the P0505 code and the behavior (sudden misfires, then normal after restart), the electronic throttle body may be sticking, failing, or needing recalibration.

• Try a throttle body reset (Google “Mercedes-Benz throttle body adaptation reset� for your exact procedure—usually involves key cycles and pedal presses).

• Physically inspect the throttle body for carbon buildup or binding.



2. Vacuum Leaks / Crankcase Ventilation Issues

• A vacuum leak (especially on the PCV system or intake manifold) could throw off the air-fuel ratio, leading to misfires across multiple cylinders.

• Listen for any hissing sounds, check hoses around the intake manifold, and consider doing a smoke test if you suspect a leak.



3. Wiring / Sensor Issues

• Check the throttle body wiring harness for any damage, loose connections, or chafing.

• Mass Air Flow (MAF) Sensor: A faulty or dirty MAF could cause air metering issues that lead to erratic behavior and misfires. Try cleaning it with MAF cleaner.

• Check battery voltage and alternator function: Low voltage can cause throttle body and ignition control malfunctions.

Steps to Try Now:

1. Throttle Body Reset – Attempt a simple adaptation reset.

2. Check for Vacuum Leaks – Look around the intake area and PCV system for disconnected or cracked hoses.

3. Inspect Wiring – Check the throttle body and MAF sensor connectors for damage.

4. Monitor Live Data (if your scan tool supports it) – Check throttle position, MAF readings, and fuel trims to see if anything is out of spec.

Next Steps if Issue Persists on Monday:

• Perform a full throttle body adaptation/reset with a professional scan tool (like a Mercedes STAR diagnostic system).

• Check for software updates—sometimes these cars have throttle calibration issues that a dealer can reflash.

• Consider a smoke test to rule out vacuum leaks.

• If no improvement, the throttle body itself may be faulty and require replacement.