My 2006 A3 2.0 with 90k miles (bought new) has been sputtering for a while when cold and the engine light would come on every so often. Also mileage was down at least 3 mpg.
Computer always said random cylinder or #4 cylinder miss-fire. Dealer said to try some fuel additive – which I did for 3 weeks. Sill having same problems.
Decided to have my mechanic, a very good guy, change out the #4 injector. This is a big job that requires intake manifold removal. While he was there he saw the back of the intake valves (all 8) were very cruddy. He cleaned them up – another big job to scrape out and remove the stuff as we did not want it getting into the cat converter. One cylinder had the intake valves open so he covered the entrance with a gasket of some type while he scraped.
Attached is an image of what he got out. I’m not sure this is all of it. He took some pictures of the valves and I’ll try to add them later. As I said, they were crudded up pretty good.
I picked it up and it runs great. No sputtering when cold and acceleration seems noticeably better. Also, interestingly, the engine is quieter. I swear the normal growl of the 2.0 had gotten quite a bit louder and now it’s quiet again.
A few notes. This was a ~6 hour ~$680 job including the $100 injector. He also replaced the temperature sensor while he was in there, so it could have been that or the replaced injector that was the problem – but I’d bet it was the valves.
Then again, why would crud on the back of the valves cause a problem? If the crud crept round the edge and caused the valve to not close just right, wouldn’t it get burned off during combustion?
A fuel additive would not help this at all ‘case it is the intake valves and they never see gas (due to direct injection). Since the intakes only see filtered, air how do they get dirty? I’ve read somewhere the PCV valve may contribute to this.
Also, this certainly is a design flaw and Audi should have a fix for it.
Also, I might want to buy a new A3 when they show up next month. Do they have the same problem – both the 1.8 and 2.0 versions?
GM has had problems with direct injection intake valves and other German cars too. Don’t think Ford had noted it. How long has Ford had direct injection? Read somewhere that changing the valve timing momentarily once in a while to clean the intakes might work.
If I knew about this and had to spend $600 every 90,000 miles – that might be OK, for this otherwise great car. Just wish I would have known about it.