4.6is diesel-like sound at idle

[g300d]

Ok, so the 4.6 now has the diesel-like idle.

Research indicates possible causes as VANOS or timing chain tensioners?

Any other possible causes, and any tips to confirm which it is?

It has 43k miles.

[Plattus1000]

Vanos. Don't worry about it till you decide to do your guides. It won't really hurt you.

When you do the refresh, you can fix it fairly easily.

[X53Jay4.8is]

Originally Posted by g300d

Ok, so the 4.6 now has the diesel-like idle.

Research indicates possible causes as VANOS or timing chain tensioners?

Any other possible causes, and any tips to confirm which it is?

It has 43k miles.

More likely to be VANOS but while you are in there to do the repair you might as well do the tensioners also. $4-5K at the shop or just parts and your time if you are a DIYer.

[g300d]

Thanks for the opinions so far guys!

Yeah it seems to run pretty well otherwise.

So what you guys are saying is to just do the VANOS with the infamous timing chain guide system refresh. What else to do when I do that, so I can research parts and procedure?

[X53Jay4.8is]

Originally Posted by g300d

Thanks for the opinions so far guys!

Yeah it seems to run pretty well otherwise.

So what you guys are saying is to just do the VANOS with the infamous timing chain guide system refresh. What else to do when I do that, so I can research parts and procedure?

I am not so sure about guides on the 4.6is. I know that the guides are far more common on the 2004-2006 4.4L and 4.8L engines. If your are getting the cloud of smoke while idling then perhaps the guides are need of replacing. I have replaced a number of vanos units on various BMW V8s and while I am in there i have done the tensioners, timing guides, timing chain, tensioner, cooling system overhaul, and all timing cover seals. If the vehicle has 100k or nearing 100k I change all of the hoses to minimize the presence of leaks.

[g300d]

Sorry, meant timing chain guide rails, as I understand they can break on higher mileage 4.6's.

[X53Jay4.8is]

Originally Posted by g300d

Sorry, meant timing chain guide rails, as I understand they can break on higher mileage 4.6's.

Okay understand and this makes more sense from what I understand about the BMW V8 engines.

[mam4.6]

Originally Posted by X53Jay4.8is

I am not so sure about guides on the 4.6is. I know that the guides are far more common on the 2004-2006 4.4L and 4.8L engines. If your are getting the cloud of smoke while idling then perhaps the guides are need of replacing. I have replaced a number of vanos units on various BMW V8s and while I am in there i have done the tensioners, timing guides, timing chain, tensioner, cooling system overhaul, and all timing cover seals. If the vehicle has 100k or nearing 100k I change all of the hoses to minimize the presence of leaks.

Just to clarify in my own mind, it's the facelift N62 engines (4.4-4.8) that have the smoking on idle issue because of bad valve stem seals, right? And it's the pre-facelift M62 engine (4.4-4.6) that has the timing chain guide issue? If I remember correctly, chain guides are reommended maintenance at around 100k miles...

[crystalworks]

Originally Posted by mam4.6

Just to clarify in my own mind, it's the facelift N62 engines (4.4-4.8) that have the smoking on idle issue because of bad valve stem seals, right? And it's the pre-facelift M62 engine (4.4-4.6) that has the timing chain guide issue? If I remember correctly, chain guides are reommended maintenance at around 100k miles...

Correct. I think they had a signal crossing up above with "guides" rather than "seals."

Pre LCI will be guides/tensioner/chain and post LCI will have valve stem seal problems. I know both of the post LCI X5's I've owned need the vss done.

[X53Jay4.8is]

Originally Posted by mam4.6

Just to clarify in my own mind, it's the facelift N62 engines (4.4-4.8) that have the smoking on idle issue because of bad valve stem seals, right? And it's the pre-facelift M62 engine (4.4-4.6) that has the timing chain guide issue? If I remember correctly, chain guides are reommended maintenance at around 100k miles...

Yes I am in agreement with this. I have had a couple of 4.6is and this being the 3rd one no valve stem seal problems like the N62 4.4 & 4.8L engines.