I'm a newbie on this forum and Audis. Just bought my 07 A4 last weekend. I noticed it is just a tad rough at idle, to the point I can see the headlight projection shake when idling in drive. Also has suction on oil cap when I pull it off with engine idling. You can hear the motor get rougher when I do that. I've searched the forums and came to the conclusion it's a stuck PCV valve. Bought the $200 kit from europarts.com. Installed the valve and breather tube. Does same thing still.

I'm hoping to get some advice. I though if you had suction on your oil cap (and subtle oil blow-by from cap onto ignition coil) it was a bad PCV ?!

Next step will be new OEM Bosch plugs, but I know this will not change the vacuum pressure on oil cap, but maybe smooth out the idle? It got 30+ mpg on my 6 hr road trip home from buying it... And it feels strong, but I have NO previous comparison for this car.

 

i havent replaced the pcv but im pretty sure that taking off the oil cap with the engine running is gonna make it run funny/rough no matter what. and i think there should be pressure/suction while running as well, that what a vacuum is. you can take the oil dip stick out while running and it should act up then too

 

If that's true, I wish I would have known that before I dropped $200. I could have used that money on many different parts I want more.

 

yea sorry to burst your bubble. but welcome to the forum, there is a ton of info on here so search around or ask. there should be someone on here that has an answer for ya
or google and check out audizine

 

Few other things to look into would be replacing N80 purge valve, fuel filter, and checking mount conditions. The rubber oem snub mount for example deteriorates and cracks.

Also, a carbon cleaning would be useful if you don't know how well the previous owner took care of the car.

Keep in mind FSI engines do idle a bit rougher than others, but you mentioned the headlights shaking and that does sound rougher than it should be. Usually with rough idle the PCV is the first thing to check, and replacing it was a good idea anyway if the car just had the original since they are common failure points.

Good luck.



Cheers.

 

Damaniac- Looks like you gave me a few things to Google or search for, thank you. I've read about the snub mount. Not sure how accuarate it looks when its installed, but the portion I can see sticking out and around looks fine. At least its not cracking and crumbling away. Sounds like replacing those is a PIA with having to remove the front end. Probably do that when it's time for a timing belt.

N80 purge valve? That's different than the diverter valve I have read so much about? I plan on removing the diverter valve just to inspect which one I've got, and make sure its not torn if it is indeed the rubber style.

How do you do a carbon cleaning?

 

sorry to disagree again but the snub mount isnt that hard. i plan on doin mine this summer. here is a diy from audizine.
DIY: B7 A4 Snub Mount Installation

also, if you dont already know, ecstuning.com has tons of audi parts and accessories for decent prices

 

Are you running other equipment? My idle gets rougher when the rear defroster and seat heaters are turned on. I guess the extra electrical load puts more strain on the alternator making the engine run rougher. Also a easy way to help clean the carbon out of the engine, is actually found and recommended in the patent paperwork Audi/VW wrote for the 2.0t FSI. Run your engine at least at 3000 rpm for 20 minutes. It increases the operating temperature to a point that the carbon comes off the special metal alloy intake valves. If you have a manual, that would be at least 4th gear at 60mph or 5th gear at 75mph. It's a variation of what is known as the "Italian tune up". "AKA" run the engine like hell for a while, and it will blow out the carbon from a direct injection engine.

 

Wow, after reading that write up, it is MUCH easier than I initially thought. Guess I have to be careful interpreting people's comments of "you have to disassemble the front end".

 

yea ive slowly learned that people like to use vague terms or do things the hard way. multiple sources is always good to help clarify