Bad allroad week. First my front airbags go flat now there is a noise coming from the engine. I have a 4.2 and I only hear the noise at idle when the engine is warm. The sound goes away with the rpm at 1000. From higher RPM when I let off the throttle it drops to idle a second or 2 before the sound starts again. It is not a consistent whack whack like a rod or piston (or diesel) but rather each sound is audibly different from the previous sometimes louder, sometimes softer. The sound speeds up as the engine speeds up, is definitely inside the engine, is metallic, and again disappears around 1000 rpm.

The sound cannot be heard inside the car at idle. There is no loss of power so on the road with the windows up there is no clue there is something wrong. If my neighbor hadn't told me I might never know. In fact, I have no idea how long this has been happening. It was last in the shop before Christmas.

Anyone have any thoughts?

 

Yesterday it took about 4 miles of city driving before the noise began. I pulled over and began playing with the throttle and realized from noisy idle as I very gentrly press the accelerator the idle gets rougher and at the same point it smooths out the noise goes away! same on the down side ... when it hits idle it is smooth and when the noise starts a few seconds later the idle gets rough. I'm thinking the noise is detonation and the culprit is ... egr????

 

Did you ever solve your noise problem?

My wife heard a "rattling" from my '04 4.2L allroad as I pulled into the driveway yesterday.

It is new to me and seems to have some growling noise on startup too.

I'm hoping it's not the timing chain guides going bad.

Thanks,
TC

 

I had a similar sound from my 4.2 and eventually the timing guides broke .. which means you have to drop the engine to fix as they chains and guides are in the rear of the engine and its the only way to get to them .. very expensive

 

I had same problem on my 4.2 allroad and it was the chain guides that ultimately broke .. had to drop the engine to repair

 

Did you do the timing chain work yourself or take it to a shop?

Curious how much time/cost this took as I'm fighting a similar possible task on my 2005 AR 4.2

Any specifics on what you did, maybe when you did it and how many miles you have had on it since would be great to hear.

Thanks...

 

I had a non Audi shop do it but they didn't quite get it right ... apparently they when reinstalling the chains they are off by a tooth on one of the gears so the timing is off ..

In any case it requires dropping the engine and there may be other issues than simply the chains and guides .. it's going to be expensive so best advice is find someone who you can trust to not "add work" but can also get it right
..

 

Also ... mine happened at 72,000 miles ... even with timing problem still going at 101,000 miles but not sure if I'm damaging anything

Expect at least 40 hours to drop and reinstall engine, plus actual repair and parts

 

Thanks a bunch for the prompt feedback Caryaudi, most appreciated!

Roger that on the advice of finding a good shop. The information online has helped me be an informed geek (I'm a computer geek by trade, but mechanical enough to understand and probably be dangerous around Audis).

I've got an appointment at two local shops in town, will see what they say. I may post a new thread on this one as I would not mind some Audi fan opinions/thoughts. Could be an expensive bill, but I really dig the AR and am willing to put money in if I can make sense out of it.

Kind regards, Pop