My wife's 2004 1.6 A3, BGU engine type, has a problem when sat in traffic at idle.

The RPM is sometimes lumpy, and sometimes it slowly climbs to around 1100ish rpm before dropping. back down to 700ish and starting to climb again.  Then, just to confuse matters, sometimes, it will sit, rock solid at 650-700 rpm.

When driving, there is no sign of the problem whatsoever, the car pulls just as well as my 1.6 VW Golf which has no issues.

Initially I suspected an air leak, so I changed a bunch of hoses that were cracked/broken including the crankcase breather pipe and the main air intake pipe (from the airbox to the throttle body) and this has reduced the severity of the above symptoms, but got rid of them entirely.

I have a few error codes using a small (cheap) code reader:

16891, Idle control system, RPM Higher than expected.

16784, EGR valve malfunction.  (this one hasn't returned since I erased it today before a long drive)

And 2 codes that I couldn't find definitions for 05523 and 04755.

Should the EGR valve be my next point to look at? The car recently had a new fuel and air filter, and had 4 new plugs about a year ago.

Any help would be gratefully received!

 

its a pain as you only have a cheapo reader. have you checked the codes against audi's version of what they are? remember they are manufacturer specific. additionally Vag Com will tell you when the code was stamped and if it has occurred since the last clear. 

being a petrol air would be my first suspect. although i know that a dodgy EGR valve can cause dodgy idling on a diesel, so maybe it can on a petrol. on diesels you can normally disable the EGR as simply as removing a vac pipe, might be worth checking if thats the case for your car? it will likely throw a fault and engine light but if it that causing you problems they should go,. take a look at the EGR and see if it has a small vac pipe going to it, if it does, remove it and stick a screw in the pipe and tie wrap it somewhere safe.

Ah, thanks, ill try that to see what it does. 

Is there an somewhere to find the audi codes? I've looked on Ross tech and haven't found anything for the 2 unknown codes as well as a few other random websites?

 

Thanks for your help.

let us know how you get on. sorry i can;t be any more help, my only exposure to petrols has been 2 stroke motorbikes and old ford granadas  when i was a kid banger racing, no egrs, or ecus on them! 

 

no idea, they could be being read incorrectly by your reader mate. 

So this is a vid I got today of what it is doing.  Also, sometimes, under revs, there is a bit of white smoke and occasionally a bit of a rattle?

 

 

video-1495465905.mp4

my 530d did exactly that when the egr went on it. 

Did you get the smoke as well?

 

20 hours ago, rbdazza said:

let us know how you get on. sorry i can;t be any more help, my only exposure to petrols has been 2 stroke motorbikes and old ford granadas  when i was a kid banger racing, no egrs, or ecus on them! 

Gonna have to start calling you 'DieselDazza''  :-)

16 hours ago, Ribenaberry1980 said:

Did you get the smoke as well?

 

yes. a faulty egr will potentially allow too much exhaust gas into the inlet manifold when on idle, causing the symptoms you describe. 

you'll lose nowt trying it, if it makes no difference you can tick it off the list

21 minutes ago, Trevor said:

Gonna have to start calling you 'DieselDazza''  :-)

haha, can't beat 'em! 

Brief update on this problem.

I replaced the EGR valve, and the problem seems to have gone! Woohoo!, but is replaced buy a different (but nowhere near as serious) issue.

My wife is saying that driving through town, stopping starting etc, the car occasionally hesitates under acceleration.

The only code in the system is 16556 - System too rich, Bank 1.

So I suppose my question is, as I only changed the EGR Valve last night,(She drove it 40 miles to work) do I need to give the car time to relearn its fuelling etc? before I start smoke testing and checking sensors and the like?

Also, Thanks for you advice so far!

 

how does that song go... If it ain't one thing it's a mother fuc...

glad the situation has improved mate. too rich or lean on a modern fuel injected car is a pain. what i would do is drive the car a few days, clear the code, then see if it comes back. if it doesn't then great, if it does, try driving the car with the EGR vac pipe removed and blocked. 

what you really need now is someone with vag-com to see what is going on