2003 RS6 engine issues...

[Marcin]

Hi all,

This is my first post here as I only bought my RS6 very recently. It's a 2003 one with 98K miles on the clock that made only about 5k miles in the last 8 years. On the initial check, the engine ran uneven but, I was sure it had to do with a lack of use/old petrol, etc as it was sitting in a garage.

After a couple of days and the Liqui Moly system cleaner consumed the issue is still there. The engine feels like a misfire once the accelerator is tapped from the idle, during drive it hesitates on acceleration, lacks power, and seems like not running on one cylinder which is very pronounced between 2-3K RPM. There are no faults in the engine giving me any indication of where to start my investigation. The car was "serviced" by the "dealer" but, I have serious concerns about the quality of their work.

This weekend I will go check the obvious things like leaks around the intake ect, I appreciate any help as I do not have much experience with these engines.

Thanks for any help and advice!

[srichards]

Take it to a specialist to have it looked at. It'll save a lot of time and effort. Unit 20 up in the North West is considered the go to place but that might be too far away.

Could be anything at all. Fresh VPower is also a good idea. It keeps the octane a lot longer than a lot of the others.

Battery is one obvious to check too. Mine was always an arse when it wasn't generally kept on a 12 battery conditioner. I keep it on a ctek all the time and just leave it off for a few days now and then. Check the voltage and if you have a way of testing the battery health then it that's worth doing.

[Marcin]

Take it to a specialist to have it looked at. It'll save a lot of time and effort. Unit 20 up in the North West is considered the go to place but that might be too far away.

Could be anything at all. Fresh VPower is also a good idea. It keeps the octane a lot longer than a lot of the others.

Battery is one obvious to check too. Mine was always an arse when it wasn't generally kept on a 12 battery conditioner. I keep it on a ctek all the time and just leave it off for a few days now and then. Check the voltage and if you have a way of testing the battery health then it that's worth doing.

Thanks srichards! You are correct, I will give it one go at the weekend, and if I cannot see anything obvious the car will go to a specialist to get it sorted. The battery is probably the strong point, only 2-year-old Bosch yoke.

[Shoppinit]

Could be anything. Cool packs, air leak, fuel pump or pressure regulator.

Are there any fault codes?

If you bought the car at a dealer consider taking it back for a refund.

[Marcin]

Could be anything. Cool packs, air leak, fuel pump or pressure regulator.

Are there any fault codes?

If you bought the car at a dealer consider taking it back for a refund.

Thanks Shoppinit, there are no fault codes which is very weird. Bringing it back to the dealer would be the last option as these cars do not exist in Ireland, currently 0 for sale. Also, as I found out they have no capacity to fix it themselves... car was meant to be checked as I highlighted uneven engine run. As long as it's nothing too serious I don't mind taking a small hit to fix as I do love the car.

[Shoppinit]

Fair enough.

Get a Vagcom then. You’re shooting in the dark without one.

Then we’ll go through things methodically.

Do a compression test too before going much further.

[Marcin]

Fair enough.

Get a Vagcom then. You’re shooting in the dark without one.

Then we’ll go through things methodically.

Do a compression test too before going much further.

I have an original Vagcom and Obdeleven but like you said, I will start with a compression test. What I noticed during log checking yesterday is, once acceleration is pressed from idle cylinders 2 and 3 ignition gets instantly retarded by approx 1.5 to 2 degrees. It doesn't happen on the other 6 pots.

[Shoppinit]

Start by logging the air flow and trim values. It takes a few starts for warning lights to come on if the dealer has cleared them just before you drive off with the car.

Might be a dodgy map. Might be worth flashing the standard map back on to the car.

After compression test then do a fuel pressure test.

The retardation is probably in response to the knock sensor adjacent to those cylinders. There are only 3 knock sensors for 8 cylinders so I don’t know how accurately it can pinpoint which cylinder is pinking.

You could swap all the coil packs from bank 1 to bank 2 to see what affect that has. It’s all good info.

[Shoppinit]

I’m also willing to bet a beer at this point that you have a massive air leak.

[Marcin]

Start by logging the air flow and trim values. It takes a few starts for warning lights to come on if the dealer has cleared them just before you drive off with the car.

Might be a dodgy map. Might be worth flashing the standard map back on to the car.

After compression test then do a fuel pressure test.

The retardation is probably in response to the knock sensor adjacent to those cylinders. There are only 3 knock sensors for 8 cylinders so I don’t know how accurately it can pinpoint which cylinder is pinking.

You could swap all the coil packs from bank 1 to bank 2 to see what affect that has. It’s all good info.

Thank you! This will keep me busy for the weekend. Yes, the car is remapped which could add to the problem. But for now, it doesn't even push the standard power. I don't know how accurate function blocks 120 and 122 are but according to it, the engine max torque under load is around 440nm and something is limiting the max actual boost in block 115 which is only around 1450mbar and is aligned with the specified one.

I will give it a go and as long as the compression is OK... there is hope

[Marcin]

I’m also willing to bet a beer at this point that you have a massive air leak.

Nothing is impossible at this stage

[Shoppinit]

The boost will be limited if there are other issues. It’s not helpful at this point other than to confirm the ecu isn’t happy about something.

The torque values you refer to aren’t going to be helpful. It’s just a rough theoretical calculation that the TCU will use to do its thang.

[Marcin]

The boost will be limited if there are other issues. It’s not helpful at this point other than to confirm the ecu isn’t happy about something.

The torque values you refer to aren’t going to be helpful. It’s just a rough theoretical calculation that the TCU will use to do its thang.

Oh poor ECU has plenty of reasons to be upset...

For now, I will start with a compression test, and check for air leaks, and fuel pressure. This should answer a couple of questions.

Thank you for all the help!!

[Marcin]

I’m also willing to bet a beer at this point that you have a massive air leak.

Update after the weekend work:

1 - Compression test done:

1 - 224 psi, 2 - 225 psi, 3 - 224 psi, 4 - 224 psi, 5 - 222 psi, 6 - 210 psi, 7 - 215 psi, 8 - 220 psi

These values seem higher than the spec... hmmm

2 - Sparkplugs checked, old and worn (dealer "forgot" to put new ones in) tapped them down to 0.7mm, new ones ordered.3 Sparks were loose!!! All connections were cleaned with the contact cleaner.

3 - The Airbox was found loose, and the mounting bolt was missing also all nipples were broken away. Also, MAF sensors cleaned seals lubricated with the silicone spray to soften them up - new ones were ordered.

4 - Fuel filter was replaced as the dealer "forgot" to change it again.. despite the car sitting in the garage for a long time

5 - Engine flushed and correct 5W40 oil put in + new oil filter as the dealer "forgot" to replace it again...

6 - General inspection - a couple of leaks which will need further investigation found, a couple of screws missing... one from gearbox sump , turbo control vacuum lines worn I need to find replacements.

RESULT - Car feels way better, all the issues are gone she pulls nice and smooth. I have another question as looking at the logs after the work the boost still seems lowish?.. correct me if I am wrong. On the full load heavy acceleration measuring block 115:

Engine load 120.3%
Boost specified 1340 mBar
Boost actual 1350 mBar

It doesn't seem right with the engine load over 100% result of remap?... and according to the description, the boost range should be between 1500 and 1800 mBar. I might go back and check the fuel pump efficiency as a hand-up... I forgot about it until the engine was hot again... fire hazard/safety first.

[Shoppinit]

That's a pretty encouraging result. Yeah, loose spark plugs would definitely cause issues. Did you order the correct NGK plugs? It's important on this car.

The engine load % isn't useful. It can (and often does) go above 100% on a stock map. I don't know what the ECU strategy is for the load so let's ignore it for now.

Your low requested boost is curious, if you have no DTC. The stock max boost is about 1750-1800 mbar (there is no min, ECU often specifies zero boost).

Now that you've fixed the issues, clear all the codes in all modules, drive the car for a few miles. Stop the engine, turn off ignition. Drive another few miles. Do this a couple of times. See if any DTC appear. Check TCU and ABS for codes in addition to ECU.

Then log a short run with partial and WO throttle. We need to log the following:

Group 002: Engine Speed Engine Load Mass Air Flow Mass Air Flow
Group 032: Adaptation (Idle), Adaptation (Partial)
Group 115: Engine Speed, Engine Load, Boost Pressure, Boost Pressure

Then another run logging the following:

Group 001: Engine Speed, Coolant, Lambda Control
Group 112: Engine Torque spec, Engine Torque actual, Torque Reduction
Group 063: Accelerator Pedal Position, Kick-Down

I'd also want to see what the EGT are reading. Can't remember where that is.

You don't have to log the groups, you can choose the individual readings.

That'll do for now. Let's see what that reveals then we can dig further.