Hey guys I have a 2007 A6 2.0T and it has a weird problem. For a few months now it has been having really bad misfires. Engine idles really badly, especially on cold start. A couple of times while driving, it got so bad that the CEL lights come on and the car went into Limp mode. Had to stop the car by the roadside and turn it of for 10-15mins before being able to drive without limp mode.

Plugging in my obdeleven, I get some codes. P1093, P0300, P0302, P2177. Have cleared the codes a couple of times and the one that keeps popping back is P0302(cyl 2 misfire) and P2177(system too lean off idle, Bank 1). The other two come up intermittently.

Initially suspecting it to be bad plugs, I changed them. Swapped out the plug coils too but same codes come up. Next thought in my mind would be bad injectors. But here's the kicker. I bought a new car and the A6 has been sitting around maybe driven once a week. Recently fuel went to reserve and to my surprise, all the problems disappeared. Car drove beautifully without any codes being thrown up. I went to the petrol station and filled up like 15L and the car started to run bad again. Drove around till reserve and Voila, car is running beautifully again. The engine idles well on a cold start too when on reserve. At this point I'm left scratching my head and my interim solution is to keep the car perpetually on reserve fuel, but it isn't a practical solution.

Has anyone ever experienced this before? What could possibly be the problem?

 

What grade of gas are you using? Needs to be premium.

 

Have only ever used 95 or Vpower 98. Definitely not an issue with the fuel used as since the time this issue came up, I have filled up at multiple petrol stations, with the same results.

Another point to take note that I didn't mention earlier is even when the misfires happened, it only happened below 2700-2800 rpm. The car will run rough and suddenly surge when rpm hits 2700. As long as the rpms are above that, the car drives and pulls fine. I have also resorted to running the car in manual mode and keeping it in low gears to mitigate the issue, but this of course has made an already inefficient car even more inefficient. Im getting like 18-20L/100km on average 😂

 

When was the last decarb service?

Can try a can of injector cleaner additive in the fuel tank with a fill.

 

That really won't do much of anything, with direct injected engines of any kind.

 

I have seen some injector pin hole ports carbon over which can alter and or reduce fuel spray. Also it is possible to resolve a stuck open injector if carbon contamination is holding the injector pintle and seat open. Certainly can’t hurt to try but the additive has to be specifically for direct injection.

 

Sure anything's possible.
My experience with my car and the 10 injectors that came out of it and got cleaned up is that it is much more likely that the filter basket has disintegrated and is now jamming the injectors open.
If it were me I would do a complete carbon cleaning, pull the injectors and run them through an ultrasonic cleaner in three different steps. And then replace all of the seals and the filter basket before reassembling.

 

If you would rather not clean and rebuild them them yourself, you can ship them off to Injector rehab and they will also run them through a set of tests as wall

 

It seems that the general consensus is that there's something wrong with the injectors. Was hoping that due to the weird symptoms it might be something else. And I guess it kind of makes sense. I'll have a go with the injectors, either replacing them or rebuilding/servicing whichever is cheaper/more convenient. Thanks guys!

 

Carbon cleaning is the consensus, but while you're in there you might as well do the injectors as well. It will be much cheaper to rebuild them than to replace them. It's unlikely that they're actually dead, just need to be cleaned really well