RS6 Plus C5 misfiring and misbehaving
Posted: Wed Jul 13, 2016 3:55 pm
Hi everybody!
I've recently bought an RS6plus with the engine misbehaving...
I knew what i was buying and being previously an owner of 80, 100, V8, S8(D2), A6(C5,2.7tt), A8(D3) I am quite familiar (at least in general terms) with how it all works.
But still - it turns out, I need your help!
So here is my story.
The engine is not stable. The idle run is floating +/- 5% - can't see it on the tachometer, but can feel it.
At the full-throttle first of all it feels like the engine is not giving it's full power.. it feels like something is holding the car's rear bumper, like she wants to ride and something is not letting her do that. the torgue, the acceleration is not smooth. From time-to-time (while holding the throttle pedal down) she suddenly shows her full power for a period and then back again (and then again - suddenly she awakens abruptly, then again half-power)...
Here is what the computer says:
What I tried already:
checked intake for leaks - didn't find any leaks;
checked turbo pressure - up to 2.2 bars (also see below);
checked air consumption - up to 300 l/s at full power (also see below);
swapped spark plugs and coils. got much better, but still no there.
swapped Mass Air Flow sensors - no significant improvement, so I put back my old ones (tests below - with the old ones)
I did a few road-tests, here is what i got:
and a couple of graphs:
Conclusions:
MAFs are fine.
Lambdas are fine. (Or should I take a look at some other lambdas measurements? There are many and I get lost in them)
Turbos are fine, except for strange wastegate behavior.
up next:
- Swap fuel filter, flush fuel system (probably won't cure, but still a good thing to do);
- Swap: N112 Secondary Air injection valve, N249 actuator, Diverter Valves, Fuel pressure regulator;
- I did not order N75 Wastegate actuator, looks like it works.
Am I on the right path?
I've recently bought an RS6plus with the engine misbehaving...
I knew what i was buying and being previously an owner of 80, 100, V8, S8(D2), A6(C5,2.7tt), A8(D3) I am quite familiar (at least in general terms) with how it all works.
But still - it turns out, I need your help!
So here is my story.
The engine is not stable. The idle run is floating +/- 5% - can't see it on the tachometer, but can feel it.
At the full-throttle first of all it feels like the engine is not giving it's full power.. it feels like something is holding the car's rear bumper, like she wants to ride and something is not letting her do that. the torgue, the acceleration is not smooth. From time-to-time (while holding the throttle pedal down) she suddenly shows her full power for a period and then back again (and then again - suddenly she awakens abruptly, then again half-power)...
Here is what the computer says:
Code: Select all
VIN: WUAZZZ4B95N999163 Mileage: 202080km/125566miles
-------------------------------------------------------------------------------
Address 01: Engine Labels: 077-907-558-BCY.lbl
Part No: 4D1 907 558 F
Component: 4.2l V8/5VT G 0001
Coding: 0010752
Shop #: WSC 13364 153 403078
VCID: 316F6586AB5E3096243-5072
6 Faults Found:
17985 - Right Engine Mount Solenoid Valve (N145)
P1577 - 004 - Open Circuit
18393 - Coolant Control Module 2 (J671)
P1985 - 002 - Malfunction - Intermittent
18308 - Coolant Fan Control 2
P1900 - 004 - Open or Short to Ground - Intermittent
18010 - Power Supply Terminal 30
P1602 - 002 - Voltage too Low - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 001 - - Intermittent
16688 - Cylinder 4
P0304 - 001 - Misfire Detected - Intermittent
Readiness: 0000 1000checked intake for leaks - didn't find any leaks;
checked turbo pressure - up to 2.2 bars (also see below);
checked air consumption - up to 300 l/s at full power (also see below);
swapped spark plugs and coils. got much better, but still no there.
swapped Mass Air Flow sensors - no significant improvement, so I put back my old ones (tests below - with the old ones)
I did a few road-tests, here is what i got:
- Why did the Wastegate open fully at full throttle at low RPMs(<2500)??
This causes the discrepancy between Specified and Actual Boost Pressures...
- I don't understand how Engine load can be 170% ??
MAFs are fine.
Lambdas are fine. (Or should I take a look at some other lambdas measurements? There are many and I get lost in them)
Turbos are fine, except for strange wastegate behavior.
up next:
- Swap fuel filter, flush fuel system (probably won't cure, but still a good thing to do);
- Swap: N112 Secondary Air injection valve, N249 actuator, Diverter Valves, Fuel pressure regulator;
- I did not order N75 Wastegate actuator, looks like it works.
Am I on the right path?