Idle Trouble - '96 A4 2.8 QUATTRO
01-25-2003, 05:18 PM
#1
AudiWorld Super User
Thread Starter
Join Date: Jan 2003
Posts: 9,298
Likes: 0
Received 0 Likes
on
0 Posts
Idle Trouble - '96 A4 2.8 QUATTRO
My A4 has had a poor idle for the last 30,000 miles. Neither the dealer nor an independent shop were able to find out what's really wrong. So far I have spent about $1,200 on troubleshooting and grappling in the dark.
My car's idle speed seemed always a bit low to me at about 800 RPM (a bit higher with the AC on), but at least it was rock-steady.
About 1 1/2 years ago the idle became rougher and the RPM got lower and lower (down to about 650-700RPM).
The dealer didn't find anything wrong (no codes), neither did an idependent shop. Yet they all agreed the idle was low and rough.
Eventually the idle speed began randomly "dipping" all the way to 0 and the car would usually stall or sometimes recover (after all the idiot lights came on!). That trend increased to a point when the car would stall as soon as I got of the gas. As I said, it did that randomly. Sometimes the car would idle just fine.
The dealer replaced my EGR valve and although the idle was still rough (they acknowledged that) it didn't stall anymore for another 10,000 miles or so.
Now it's back to rough idling and stalling, and it's worse than ever.
I also noticed that the idle is better while the engine is still warming up. It also seems cold weather makes the car stall less than warm weather...
I removed my MAF sensor (which was a bit dirty) and cleaned it. That seemed to help, but only temporarily. I'm not sure if the improvement was due to cleaning the MAF sensor or if it was unrelated.
Now I'm thinking idle control valve, EGR valve (where exactly do i find that?), or carbon buildup in the throttle body.
I'm not a grease monkey extraordinaire, but at this point I'd rather try finding what's wrong myself than shelling out more for little to no results.
If anybody has a suggestion, I'd be very happy. :-)
Cheers,
-moribundman
PS: I don't use kangaroo gas!
My car's idle speed seemed always a bit low to me at about 800 RPM (a bit higher with the AC on), but at least it was rock-steady.
About 1 1/2 years ago the idle became rougher and the RPM got lower and lower (down to about 650-700RPM).
The dealer didn't find anything wrong (no codes), neither did an idependent shop. Yet they all agreed the idle was low and rough.
Eventually the idle speed began randomly "dipping" all the way to 0 and the car would usually stall or sometimes recover (after all the idiot lights came on!). That trend increased to a point when the car would stall as soon as I got of the gas. As I said, it did that randomly. Sometimes the car would idle just fine.
The dealer replaced my EGR valve and although the idle was still rough (they acknowledged that) it didn't stall anymore for another 10,000 miles or so.
Now it's back to rough idling and stalling, and it's worse than ever.
I also noticed that the idle is better while the engine is still warming up. It also seems cold weather makes the car stall less than warm weather...
I removed my MAF sensor (which was a bit dirty) and cleaned it. That seemed to help, but only temporarily. I'm not sure if the improvement was due to cleaning the MAF sensor or if it was unrelated.
Now I'm thinking idle control valve, EGR valve (where exactly do i find that?), or carbon buildup in the throttle body.
I'm not a grease monkey extraordinaire, but at this point I'd rather try finding what's wrong myself than shelling out more for little to no results.
If anybody has a suggestion, I'd be very happy. :-)
Cheers,
-moribundman
PS: I don't use kangaroo gas!
01-25-2003, 05:35 PM
#3
AudiWorld Super User
Join Date: Dec 2001
Posts: 22,571
Likes: 0
Received 0 Likes
on
0 Posts
Did they replace vacuum hoses or look for clogged hoses leading into the throttle body
plenum? My 97 2.8 idles at about 700rpms, which is normal. It doesn't dip down like yours does though. I had rough idling problems in the past and I replaced all my rubber vacuum hoses with Silicone and cleaned out a few clogged plastic hoses that lead into the black plenum between the airbox and throttle body. This fixed my issue.
The EGR valve is mounted on the driver's side of the intake manifold near the back of the manifold.
The EGR valve is mounted on the driver's side of the intake manifold near the back of the manifold.
01-25-2003, 05:50 PM
#6
AudiWorld Super User
Thread Starter
Join Date: Jan 2003
Posts: 9,298
Likes: 0
Received 0 Likes
on
0 Posts
Good point!
In fact, I have a 5" mystery vacuum hose come out of the throttle body (about 3 1/2 inches below the point where the throttle cable goes in the housing). Nobody has ever been able to find to what that is supposed to be connected. They plugged it with a screw... :-(