Audi S8 D3

Rémon · Sep 12, 2020

Hi,

My S8 is due for new spark plugs. The engine is standard, except for an ECU tune/REMAP.
Which plugs are best to use?

Furthermore, I keep getting these annoying codes after about 150-200 km: P0171 & P0174

Changed the fuel filter, that didn't help. Engine idle's rough when cold.

Would be very grateful for a some advice.

Homer Simpson · Sep 13, 2020

I would use plugs from Audi/TPS or the OEM equivalent.

The codes refer to a lean mixture. Have you checked the the vent hose that runs across the top-rear of the engine?

Incidentally, what gains did you get from the remap? Was it after manifold flap removal?

Homer Simpson · Sep 13, 2020

I would use plugs from Audi/TPS or the OEM equivalent.

The codes refer to a lean mixture. Have you checked the the vent hose that runs across the top-rear of the engine?

Incidentally, what gains did you get from the remap? Was it after manifold flap removal?

Rémon · Sep 13, 2020

Homer Simpson said:
I would use plugs from Audi/TPS or the OEM equivalent.

The codes refer to a lean mixture. Have you checked the the vent hose that runs across the top-rear of the engine?

Incidentally, what gains did you get from the remap? Was it after manifold flap removal?

Thank you for your response!
I found that the NGK Laser Platinum Resistor PFR6WTG/5547, should be the original plugs.
I'll order these.

I'll check the vent hose tomorrow in daylight.

The remap was done before I owned the car. The precious owner commented that the response became better.
The flaps are still in there actually. I cleaned them this summer after cleaning the ports.
It is better to remove the flaps?

Rémon · Sep 19, 2020

New plugs are on their way.

I've changed the fuel filter, installed a new battery (which wasn't performing as it should), and reset the codes.
240 km's later, the check engine light came back on.

This time accompanied with the following codes:
P1075
P1077
P0171
P0174

All saying that the system is too lean, low fuel pressure.

I checked the hose that runs behind the engine, that looks fine.

Perhaps my fuel pump is underperforming or the fuel injectors need maintenance?

Rémon · Sep 19, 2020

Turns out you were right concerning the vent hose after all. I heard a sound coming from that area during inspection today.

When moving the hose, the engine became quieter.
When I tried to take off the hose for further inspection, it broke off in two places.

These hoses become quite brittle after 14 years.
I taped it up for now to get from a to b but I'll order a new hose on Monday.

Furthermore I noticed that the connector on the hpfp, which sits on bank 2 lacked it's "clip" to connect it properly.
This will also have to be replaced.
Used some tape there as well as an emergency solution.
The fuel lines connected to this pump were also not 100% tightened, perhaps this helped as well.
Noticed that the engine idled much better and the fuel consumption went way down during my test drive.

Homer Simpson · Sep 22, 2020

I had the same problem. I got a couple of lean codes and could hear a small hiss sometimes. Checked the hose and realised it had been taped up! Got a new one fitted and it has been fine ever since. Good luck

Rémon · Sep 26, 2020

Homer Simpson said:
I had the same problem. I got a couple of lean codes and could hear a small hiss sometimes. Checked the hose and realised it had been taped up! Got a new one fitted and it has been fine ever since. Good luck

Thanks for your input! It must be the hose yes.
I've taped it up for now, driven 550 km after that, without any codes coming back.
Went to the Audi dealer to get a new hose, was shocked with the price of 300 usd!

It's basically a very simple rubber air hose.
Going to check elsewhere. Do you remember what you paid for it?
But in the meantime, the car is acting just fine. New plugs aren't installed yet, but I'm currently getting 4.5 sec. 0-100 km/h which is pretty good for this car.

Homer Simpson · Sep 27, 2020

Rémon said:
Thanks for your input! It must be the hose yes.
I've taped it up for now, driven 550 km after that, without any codes coming back.
Went to the Audi dealer to get a new hose, was shocked with the price of 300 usd!

It's basically a very simple rubber air hose.
Going to check elsewhere. Do you remember what you paid for it?
But in the meantime, the car is acting just fine. New plugs aren't installed yet, but I'm currently getting 4.5 sec. 0-100 km/h which is pretty good for this car.

Mine was around £120 so still cheaper than US prices! Glad yours is behaving itself, who would think a bit of (expensive) hose would make so much difference? lol

Rémon · Sep 29, 2020

Homer Simpson said:
Mine was around £120 so still cheaper than US prices! Glad yours is behaving itself, who would think a bit of (expensive) hose would make so much difference? lol

Actually, I live in Norway where we use norwegian kroner as a currency but I thought to convert it to USD, figured that might be more convenient.

That's quite a difference, that's like half the price!
It's still holding up after 650 km, guess it's going to last but it's best to change it the end.

Haha yes, that's what I thought. Been struggling with these codes for months.
Thanks again for your input, really appreciate it.

Now I'll wait for the plugs to arrive.
You still own the S8?

Homer Simpson · Oct 4, 2020

Rémon said:
Actually, I live in Norway where we use norwegian kroner as a currency but I thought to convert it to USD, figured that might be more convenient.

That's quite a difference, that's like half the price!
It's still holding up after 650 km, guess it's going to last but it's best to change it the end.

Haha yes, that's what I thought. Been struggling with these codes for months.
Thanks again for your input, really appreciate it.

Now I'll wait for the plugs to arrive.
You still own the S8?

You're welcome. Yes I still have my S8 and still love it as much as the day I bought it! Took me a long time to find one with a high spec and decent mileage. Hopefully will be a keeper.

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