[alexristainoN54]

I have a 2009 335i, fbo, 120,000 miles.

As the title says my vaccum at idle randomly Increased alot.
While I used to have idle vaccum at -14 psi to -17 psi, I'm now sitting at -5 psi.

Recently I took off my secondary cats making me full catless, and I'm blowing white smoke. While it's 80% probability turbos, makes me wonder if it has something to do with my recent change in vaccum at idle.

I'm doing my valve cover gasket and a new valve cover/ pcv system so well see if that fixes my two issues but seems unlikely vaccum at idle is effected by a blown turbo seal or a cracked valve cover gasket.

thanks!

[dpaul]

Originally Posted by alexristainoN54

I have a 2009 335i, fbo, 120,000 miles.

As the title says my vaccum at idle randomly Increased alot.
While I used to have idle vaccum at -14 psi to -17 psi, I'm now sitting at -5 psi.

Recently I took off my secondary cats making me full catless, and I'm blowing white smoke. While it's 80% probability turbos, makes me wonder if it has something to do with my recent change in vaccum at idle.

I'm doing my valve cover gasket and a new valve cover/ pcv system so well see if that fixes my two issues but seems unlikely vaccum at idle is effected by a blown turbo seal or a cracked valve cover gasket.

thanks!

First of all, I doubt you are reading -14 to -17 PSI at idle. You likely mean -14 to -17 in Hg (inches of mercury) which would be -6.8 to -8.3 PSI. Second, your manifold vacuum at idle has decreased a lot, not increased.

How/where are you measuring manifold pressure?

If it is really -5 in Hg at idle (2.5 PSI), you've got a significant leak and probably one that you can hear if you put your ear in there. Listen closely at the vacuum line from the manifold to the diverter valves and the diverters themselves. Maybe the manifold itself is cracked. There are a number of possibilities but if there is a leak you should be able to trace it by sound.

Did you read your codes?

[alexristainoN54]

Originally Posted by dpaul

First of all, I doubt you are reading -14 to -17 PSI at idle. You likely mean -14 to -17 in Hg (inches of mercury) which would be -6.8 to -8.3 PSI. Second, your manifold vacuum at idle has decreased a lot, not increased.

How/where are you measuring manifold pressure?

If it is really -5 in Hg at idle (2.5 PSI), you've got a significant leak and probably one that you can hear if you put your ear in there. Listen closely at the vacuum line from the manifold to the diverter valves and the diverters themselves. Maybe the manifold itself is cracked. There are a number of possibilities but if there is a leak you should be able to trace it by sound.

Did you read your codes?

Thanks for the reply.
Reading it off of MHD app.

And it is reading psi at vaccum and I've never changed the settings so it should have always been in psi.
I swear I used to see -14 psi, maybe I'm remembering wrong or vaccum used to be in hg and mhd changed it on an update.
anyways I changed valve cover, and new pcv. getting -8.5 psi at idle now.
so I guess that puts in the proper range then?
no sounds of vaccum or boost leak and I'm hitting my target psi, so I guess I'm all good

thanks again

[dpaul]

8.5 psi is normal at idle. Glad you were able to solve this problem

BTW, when people say "vacuum" in automotive systems, it is almost always referenced to atmospheric pressure, which at sea level is 14.7 PSI (or 29.9 in Hg if you prefer). Obviously, the best vacuum you can obtain would be 0 PSI which you could represent with a minus sign as -14.7. You cannot have -17 PSI.

[alexristainoN54]

Originally Posted by dpaul

8.5 psi is normal at idle. Glad you were able to solve this problem

BTW, when people say "vacuum" in automotive systems, it is almost always referenced to atmospheric pressure, which at sea level is 14.7 PSI (or 29.9 in Hg if you prefer). Obviously, the best vacuum you can obtain would be 0 PSI which you could represent with a minus sign as -14.7. You cannot have -17 PSI.

That's really good to know, thanks for all the help! You relieved me of a lot of stress and searching.

[Red_Bean_Bun]

That white smoke - I see that coming on quite often when the secondary cats are deleted.

When the secondary cats are restored - it should stop smoking ...

[alexristainoN54]

Originally Posted by Red_Bean_Bun

That white smoke - I see that coming on quite often when the secondary cats are deleted.

When the secondary cats are restored - it should stop smoking ...

it's definitely from the cat delete, but I don't think the cars are the root cause, at idle in warm up I get more smoke than I used to, but an acceptable amount. when I get warm and drive it's bellowing smoke.

It's likely the turbos, but makes me nervous that it could be a piston rings.

need to get a compression test and leak down test before doing the turbos for peace of mind.

I'll let y'all know though, this issue seems to be illusive for a lot of people.

[alexristainoN54]

problem solved, two issues:

1. intake manifold was coated in oil and was dripping into the engine at times causing the smoke.

2. Some lazy cheap idiot at Hendrick BMW replaced one injector to index 11 while the others are index 7 and 8. (big no no to mix index 11 with anything lower in the same bank).

so for those who can't find the smoke issue. check your injectors and clean your intake manifold!!!