Intermittent Misfire

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4.0 V8 40v biturbo TFSI - 597 bhp (Performance)
Leo-RS
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Re: Intermittent Misfire

Post by Leo-RS » Sat Jul 16, 2016 1:32 pm

Speak to Doug at MRC,

They recommended colder plugs NGKR7437-9 (NGK Racing 4654) The -9 is a colder grade plug for running higher boost applications. I'm sure the standard is -7 or -8. They told me it was important due to the number of misfire issues they were having on the standard plugs.

In addition to that, the original MRC map deactivates the cylinder on demand tech due to misfires occurring where you would be in 4cyl mode or close to 4cyl mode on light throttle and then plant the throttle or use kickdown. The actuator that controls the 8/4 switch over gets confused and it ends up causing a flickering engine light. I had it deactivated initially but then got it reactivated as I had never encountered the problem and don't usually drive in that manner. If I want to drive fast, it's in dynamic and I'm nowhere near 4cyl mode for it to get confused so I had the 4cyl mode switched back on and to date have not had any issues.

Remember it's summer, turbo cars don't really like ambient temps of 25c+ and if you haven't upgraded your plugs to colder grade then that may be part of your problem. Have you pulled out the plug from 5 to inspect it to make sure there isn't a broken tip?

Yes, Tesco 99 is the best fuel in the UK, no issues there.
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Re: Intermittent Misfire

Post by doodlebug » Sat Jul 16, 2016 1:56 pm

Come on, this isn't hot. OEM plugs should be fine. This engine is used in many applications.

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feeltheburn
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Re: Intermittent Misfire

Post by feeltheburn » Sat Jul 16, 2016 2:03 pm

Pre FL- Stock. Never noticed any sensation of a misfire- sometimes the switch from 8 to 4 cylinders can be felt so maybe this explains the count? Cylinders 1 – 4 – 6 – 7 as opposed to 1 – 5 – 4 – 8 – 6 – 3 – 7 – 2. Do you feel a misfire when the gbox is in sport as well? [4 cylinder mode deactivated by default iirc]
miss.png
Last edited by feeltheburn on Sat Jul 16, 2016 2:07 pm, edited 1 time in total.
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Re: Intermittent Misfire

Post by Paulm » Sat Jul 16, 2016 2:05 pm

Leo-RS wrote:Remember it's summer, turbo cars don't really like ambient temps of 25c+ and if you haven't upgraded your plugs to colder grade then that may be part of your problem. Have you pulled out the plug from 5 to inspect it to make sure there isn't a broken tip?

Yes, Tesco 99 is the best fuel in the UK, no issues there.
25c in the UK that don't happen often lol. Even so that's not what I would call hot compared to other countries where the RS6 is sold.

Tesco best in UK? at what? 95 base fuel with 5% bioethanol by volume added to take it up to 99. Very good at stopping det but V power is a better cleaner base fuel all round from what I have read.
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Re: Intermittent Misfire

Post by doodlebug » Sat Jul 16, 2016 2:14 pm

Tropical for Scotland!

Aye, V Power is my choice.

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Re: Intermittent Misfire

Post by Leo-RS » Sat Jul 16, 2016 2:51 pm

doodlebug wrote:Come on, this isn't hot. OEM plugs should be fine. This engine is used in many applications.
Okay, I wrote that for the good of my health there Doodlebug, just made it up and I'm lying. You caught me out :thumb:

Simply relaying what the chaps at MRC recommended and as to the reason why. The standard plugs even running standard boost have a tendency to throw up misfires but then I guess I'm lying there too.

1.2 bar upto 1.6 bar, not just in the RS6 but a lot of tuners change out the plugs for a grade cooler on all platforms. What's strange about this? Have you ever modified a car before? :shock:

Paul, if you follow MRC's Facebook/Instagram page you will see them comment frequently how Tesco 99 outperforms Shell's V power. They afterall have a dyno which is a little more accurate than your butt dyno and have won tuner of the year for about the last 8.

As to times, my car was hitting 0-100 in 6.2 back in February, yesterday when I tested, 6.6. You're seriously not trying to tell me that you're rewriting the physics books are you? You never tested Summer vs Winter performance Paul? Surprising seeing as you're a tuner yourself.

RS6's in Australia or Dubai, or California will not run the same performance times as we do here in Europe without running better cooling or higher octane. Best running NA cars in hot climates
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Intermittent Misfire

Post by doodlebug » Sat Jul 16, 2016 2:59 pm

If the OEM plugs were that problematic, and this is not about tuning, then there would be a queue around the block at every Audi and Bentley dealer. Clearly there isn't ergo there is not a problem with the choice of OEM plug.

Fuel is not all about performance. Matter of fact that supermarket fuel does not have the cleaning agents of a Shell etc.

I don't think anyone is debating that the combustion engine performs better in cooler conditions. But to say a mass produced engine requires modification to operate on a balmy British Summer's day is clearly bonkers.
Last edited by doodlebug on Sat Jul 16, 2016 2:59 pm, edited 1 time in total.

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Re: Intermittent Misfire

Post by andywaddy » Sat Jul 16, 2016 2:59 pm

Leo-RS wrote:Speak to Doug at MRC,

They recommended colder plugs NGKR7437-9 (NGK Racing 4654) The -9 is a colder grade plug for running higher boost applications. I'm sure the standard is -7 or -8. They told me it was important due to the number of misfire issues they were having on the standard plugs.

In addition to that, the original MRC map deactivates the cylinder on demand tech due to misfires occurring where you would be in 4cyl mode or close to 4cyl mode on light throttle and then plant the throttle or use kickdown. The actuator that controls the 8/4 switch over gets confused and it ends up causing a flickering engine light. I had it deactivated initially but then got it reactivated as I had never encountered the problem and don't usually drive in that manner. If I want to drive fast, it's in dynamic and I'm nowhere near 4cyl mode for it to get confused so I had the 4cyl mode switched back on and to date have not had any issues.

Remember it's summer, turbo cars don't really like ambient temps of 25c+ and if you haven't upgraded your plugs to colder grade then that may be part of your problem. Have you pulled out the plug from 5 to inspect it to make sure there isn't a broken tip?

Yes, Tesco 99 is the best fuel in the UK, no issues there.
Thanks for the info Leo. If it were a plug issue, would you not expect for it to be present in more than one cylinder instead of just 5? And if it were the plugs, would you not expect it to go away now I'm back stock?

The bit about CoD I totally agree with as when I had the tune, say if I was in comfort and cruising on the motorway at 70, then hit kickdown, it would nearly always activate the CEL for a few seconds and that's gone away now I'm back at stock.

I have swapped cyl 5 plug for a new one to help rule it out but that didn't seem to help. The original one looked pretty okay. I've still got it so will take a photo of it when I get home.

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Re: Intermittent Misfire

Post by Leo-RS » Sat Jul 16, 2016 3:05 pm

Well you know better than the UK's leading VAG tuner then Doodlebug :thumbs:

Don't believe me on the fuel or the spark plugs, pick up the phone, give Doug a bell and confirm for yourself. They recommend a plug change on a tuned car and they recommend Momentum 99 over V Power.

That's fact but argue the points all you like. As to standard car, the thread starter here is running a 16 plate car and having misfires, it may be the plugs it may not.

Jesus, the next time someone asks for input, I'll remember to point them to you Doodlebug seeing as you know more than everyone else.
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Intermittent Misfire

Post by doodlebug » Sat Jul 16, 2016 3:07 pm

But his car ISN'T tuned FFS.

Now put your dummy back in and run along.

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Intermittent Misfire

Post by andywaddy » Sat Jul 16, 2016 3:08 pm

feeltheburn wrote:Pre FL- Stock. Never noticed any sensation of a misfire- sometimes the switch from 8 to 4 cylinders can be felt so maybe this explains the count? Cylinders 1 – 4 – 6 – 7 as opposed to 1 – 5 – 4 – 8 – 6 – 3 – 7 – 2. Do you feel a misfire when the gbox is in sport as well? [4 cylinder mode deactivated by default iirc]
miss.png
Thanks for that...makes me feel a tad better!
Gearbox in sport and pushing slightly when still cold will bring on my misfire (the type which gets logged like in my original post) the majority of the time. But if I just sit there idling watching the above parameters, you'll see the cylinder 5 number increase by 2 or 3.

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Re: Intermittent Misfire

Post by Leo-RS » Sat Jul 16, 2016 3:10 pm

Andy, I know of an RS7 recently that went bang due to the spark plug tips being found broken off. The chap suffered frequent misfires and on inspection, 3 of the tips had broken off, I'll see if I can find the picture. I don't think this is the case here though as I know he was running octane booster (Toulene fouling plugs)

Doodle, you're arguing black is white my friend, what are you doing trolling RS6 forums anyway? Shouldn't you be over on the 991 forums proclaiming your excellent tuners knowledge?

I'm trying to hep the guy out seeing as we both have/had and then plan to have again MRC RS6's. Do you have an RS6 tuned by MRC? If not, then off you pop.

Image

This RS7 is having its engine rebuilt just now due to a few melted pistons.
Last edited by Leo-RS on Sat Jul 16, 2016 3:15 pm, edited 1 time in total.
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Re: Intermittent Misfire

Post by doodlebug » Sat Jul 16, 2016 3:14 pm

Sorry, you've lost the plot. You're trying to tell us that the plugs on a car with a standard tune are questionable. Tell me I'm wrong?

I'd say the best bet here is to take it to a dealer, warranty job.

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Re: Intermittent Misfire

Post by Leo-RS » Sat Jul 16, 2016 3:20 pm

I specifically said tuned cars doodlebug with a small caveat that MRC do not rate the standard plugs reliability and have cured misfire issues on standard cars by replacing the standard plugs for uprated plugs. Sure, if there are misfire issues on a standard car, then the car should go back to Audi for warranty work. In this case, there's a risk of TD1 being flagged, depends whether MRC reset the ECU back to standard.

I'm sure Andy will get to the bottom of it, it may be the plugs, it may not be, it's just a suggestion as was the fuel. (I spotted an M5 owner yesterday fill up with 95 octane fuel, I kid you not)
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Re: Intermittent Misfire

Post by doodlebug » Sat Jul 16, 2016 3:22 pm

On all of that I agree.

Worst I saw was an SLR owner fill up with cooking juice.

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