Terrible rattle noise from engine top

[scott99c2]

Guys,
Because life got in the way, I just finished up my stage 3 install. If you’ll recall, I was driving home from Ohio and my car threw an EPC and CEL for misfire on cylinder 3 and some lambda failures and went into limp mode. It was also making some mechanical noise, so I suspected the turbos.

It was NOT the turbos, but since it was a misfire and I was replacing most of the world, I figured I would find the issue. Well, I started the car today and it is still there. It’s a loud rattle, and the limp mode came right back on.

I didn’t have the bumper on when I started it so I got a bunch of errors, but nothing that pointed to what this could be. Any ideas? I suspected one of the HPFPs was self destructing, but that doesn’t sound like the culprit.

[gk1]

Are you able to narrow down where you think the sound is coming from?
Wastegate rattle?
Cylinder deactivation solenoid?
How’s the oil look? Any metal?
Timing chain/tensioner?

[wwhan]

.... Any ideas? I suspected one of the HPFPs was self destructing, but that doesn’t sound like the culprit.

What year?

There are issues with some of the pre 2017 S6/S7 for timing chain guide and cam adjusters. There are often issues with the HPFP, but mostly leaking fuel into the oil (bad seal).

Camshaft ATU: https://static.nhtsa.gov/odi/tsbs/20...50761-9999.pdf

[scott99c2]

Are you able to narrow down where you think the sound is coming from?
Wastegate rattle?
Cylinder deactivation solenoid?
How’s the oil look? Any metal?
Timing chain/tensioner?

It seems to be coming from the top of the engine on the drivers side, think cam cover, but it’s hard to tell. Oil seems fine, I did get an error when I was limping home about cylinder deactivation, but it’s not in the logs anywhere that I can tell.

[scott99c2]

What year?

There are issues with some of the pre 2017 S6/S7 for timing chain guide and cam adjusters. There are often issues with the HPFP, but mostly leaking fuel into the oil (bad seal).

Camshaft ATU: https://static.nhtsa.gov/odi/tsbs/20...50761-9999.pdf

It’s a 13, but I get no camshaft related errors like the error codes mentioned here.

[viceroy1976]

You'll get cylinder deactivation with misfires, which is pretty normal.
I think there is a threshold of a certain number of misfires before it deactivates the cylinder.

[wwhan]

It’s a 13, but I get no camshaft related errors like the error codes mentioned here.

Maybe HPFP may be a reasonable guess, if it is not Cams or Turbos.

https://static.nhtsa.gov/odi/tsbs/20...22182-9999.pdf

"01 MIL on (DTC P01C900 and P008800 - fuel rail pressure too high); noises from engine compartment
01 14 61 2035235/2 January 23, 2014."

"S6, S7 2013"

"The customer reports that the engine warning light illuminates sporadically (Figure 1).
• The engine may have reduced performance without significant loss of power or stalling.
• Noise is heard coming from the engine compartment, specifically from the High Pressure Fuel Pumps 2.
• The following DTCs are stored in the engine control module (ECM), J623 (address word 01):
• DTC P008800 (fuel, rail/system pressure too high)
• DTC P01C900 (fuel, rail/system pressure bank 2 too high)"

"Technical Background
The fuel metering valve of the high-pressure fuel pump is controlled by a specific on/off ratio. If there is a low system voltage, the on/off ratio may not be enough to keep the fuel metering valve constant in all areas. In such a situation, the fuel metering valve is deactivated and the high-pressure fuel pump switches to full supply mode. Because the increased rail pressure does not match the respective driving situation, the DTC appears.
Production Solution
ECM software update."

"SVM Update Instructions
1. Follow all instructions in TSB 2011732: 00 Software Version Management (SVM), operating instructions.
2. Update the ECM software using the SVM action code as listed in the table below if necessary.

"Model Engine Old Software Part Number Old Software Version New Software Part Number New Software Version (or higher) SVM Action Code
S6/S7 (MY 13) 4.0T CEUC 4G0906014B 0006 4G0906014B 0007 01A148"

Also on 2013 models: https://static.nhtsa.gov/odi/tsbs/20...68767-6903.pdf

[scott99c2]

Just to close the loop on this, there was an open circuit on the sensor on the driver's side HPFP sensor. If that's unplugged the car makes the worst racket you've ever heard... thought the valve train was going to come through the cam covers. Glad it was nothing serious.

[wwhan]

Just to close the loop on this, there was an open circuit on the sensor on the driver's side HPFP sensor. If that's unplugged the car makes the worst racket you've ever heard... thought the valve train was going to come through the cam covers. Glad it was nothing serious.

Good to know. Glad it is was resolved easily.

An unplugged sensor disconnects the control loop, so it is running open loop on part of the fuel system.

Low Fuel Pressure Sensor G410 & Fuel Metering Valve 2 N402 are located on the HPFP