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Discussion Starter · #1 ·
Just kidding with the title of course.

Had a check engine light for a few days and a lack of power, so I hooked up the laptop and found cylinders 6,7,8 with random misfires.

Reset the check engine light, but upon firing up the car, I had rough idle again so I'm sure it's still got trouble.

Hmmmm :confused: dealer, drop off, waiting, etc. I hate that stuff.

 

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I am interested in how you were able to check the diagnostics on your car. What software do you use for this? Where do you access the vehicle? Clearly this is way beyond my area of expertise. Please say more.
 

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Discussion Starter · #3 ·
You can order a USB kit from this company http://www.autoenginuity.com/

It's approximately $250. You connect it to the laptop via USB, and the other end goes into a module under the dash just under the headlight switch. Almost all cars have this.

I reset the engine light and drove about 40 miles today with no sign of misfire. Maybe it was a one time fluke going over 8200 RPM too many times.
 

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Discussion Starter · #4 ·
well, light is back. I drove below 8K all day, but right when i hit 8K RPM, the light came back and P0300 code which is the misfire.

Might be related to the exhaust valve vacuum if something went wrong. I disconnected those exhaust valve tubes a few weeks ago and everything was fine. I'll recheck the hoses and even put the tubes back to see if that was the cause.

Reading some google results, messed up oxygen sensors may cause this too. who knows.

Just thought I'd share this with the community :)
 

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does the USB kit allow you to change the settings on your car e.g. lights/wiper programming and that sort of thing?
 

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I've had the MIL light on twice now due to brief episodes of random cylinder misfire.

Our local Audi R8 tech says the 4.2 in the RS4 is notorious for being "hard on sparkplugs" and (as mentioned above) the RS4 initially came with a new set of plugs to be installed during PDI immediately before delivery to the customer..

What, if anything, have you gentlemen done to keep this problem from recurring?
 

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Discussion Starter · #11 ·
Well, I just stopped looking at the dash error light :)

I hate the idea of having to take the car into repair and leaving it.

My 5,000 mile service light just came on, so I guess I have no choice.
 

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I had a fault cam sensor a few months back, that I took in to get fixed. I then got the cam error again, though it went away on my drive home.

I just started it up after about 2 weeks and man was the start up rough. Revs choking up and down. Then again, it's freezing outside. After a moment at idle it sounded normal.
 

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Discussion Starter · #14 ·
Yup, same symptoms. Very rough start.

I took this in for the problem at 3K miles, the dealer told me no trouble found. I told them I read a ton of forum posts regarding bad plugs and misfire. They told me I'm wrong.

After 1-2 minutes of cold start, even taking off in first gear normally, the car suddenly jerks like some plugs decided to wake up, fire, and turn off again. Very odd.
 

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I just started it up after about 2 weeks and man was the start up rough. Revs choking up and down. Then again, it's freezing outside. After a moment at idle it sounded normal.
Yup, that's what happens to me. Starts rough, then Revs drop and nearly stalls then comes back up again and idles normally after a few seconds... Let's see what Audi says this week.
 

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My R8 starts rough on cold starts for a couple of seconds but then runs smooth at around 1200rpm until dropping back to normal idle.

I have never had it almost stall... and when driving off after fast idle the engine is silky sweet.
 

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Yup, that's what happens to me. Starts rough, then Revs drop and nearly stalls then comes back up again and idles normally after a few seconds... Let's see what Audi says this week.
I'm pretty sure this is normal. They provided me with a pamphlet that only the dealers were supposed to get and explain to the buyers. I believe rough start in cold was one of them. I also think that mine was a little rougher than normal because I hadn't driven it in a couple weeks and it's been anywhere from -5 to 15 F lately.
 

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Hmmm. fair enough WEDOUGLAS, but it never used to do this. :(

AND I realise all R8's sound louder and rougher on cold start, since there is a Bypass valve which let's more air into the CATs to reduce pollution.

However, my situation is abnormal. Only started doing this 8 weeks ago. It's not cold here ATM either. So, let's see what happens...

PS: The engine also coughs and stutters during downshifting with throttle blips... Not very smooth or lively.
 

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Reminds me of my E36 M3 - sounded like it was going to start shedding parts on cold start. Once warmed up, it performed like a champ.
 

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haven't noticed this just yet, but do keep us posted with what the dealer finds out
 
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