[Heeltoego]

Car is a 2007 335i, 100k miles, original turbos. No modifications besides suspension and LSD. The car had new plugs and the carbon cleaning done before the tune. Prior to the tune, no issues. Flashed with Cobb stage 1 Sport. Ran healthy for about 2k miles. Started to notice increased lag towards full boost (14-15 psi). Then couple weeks later started throwing 30ff low boost codes. This would only happen when the car would get hot - oil temps above 200-210. While the car was warming up, it would pull strong and make/hold full boost. I replaced all vacuum lines except for the 2 running to the turbos. No change. I flash the car back to stock and it drive completely normal, smooth power, no codes.

Anyone experience similar situations?

[Jeff@TopGearSolutions]

You still have a boost leak, it's just small which is why stock boost drives fine.

As boost increases, so does the pressure and where the pressure might be tolerable at low boost it isn't during high boost as components expand further.

If you have stock diverter valves, they may be the issue. You really need a boost leak test to be done, otherwise you are basically replacing parts blindly.

[335NJ]

FWIW, a 30FF could be related to a vacuum issue as well. If there's not boost leaks as Jeff pointed out above, test the vacuum system, and mainly the boost solenoids since you replaced most of the lines already. The ones to the turbos are just as prone to failure if not more so.

[Heeltoego]

So giving what is going on is it safer to say it's a boost leak related issue rather then the turbos going bad?

I feel like if the turbos were failing they would throw the code all the time, not just when the car get hot.

This also makes be believe that the stock diverter valves could be the problem due to their plastic components, once everything gets up to operating temp they are unable to hole the pressure. ?

[Jeff@TopGearSolutions]

We don't really know from this end as every boost leak is different. Common failure points, especially at high mileage are Vac Lines, stock diverter valves and boost solenoids.

These can all be tested or you can just replace. With the amount of mileage you have I'd get some fresh boost solenoid and new diverter valves anyway but there information out there to test them.

A quick google will yield what you need. There are some DIY threads somewhere too.

Its hard to say as the problem is so broad and could be anywhere. I doubt it's the turbo's though.

[335NJ]

http://www.n54tech.com/forums/showthread.php?t=13114

A starting point. Unfortunately, there's no way for anyone here to tell you a definitive answer since there's so many possibilities. If you can't find the issue, take it to a local Indy.

[AndyW]

Originally Posted by Heeltoego

Car is a 2007 335i, 100k miles, original turbos. No modifications besides suspension and LSD. The car had new plugs and the carbon cleaning done before the tune. Prior to the tune, no issues. Flashed with Cobb stage 1 Sport. Ran healthy for about 2k miles. Started to notice increased lag towards full boost (14-15 psi). Then couple weeks later started throwing 30ff low boost codes. This would only happen when the car would get hot - oil temps above 200-210. While the car was warming up, it would pull strong and make/hold full boost. I replaced all vacuum lines except for the 2 running to the turbos. No change. I flash the car back to stock and it drive completely normal, smooth power, no codes.

Anyone experience similar situations?

My car is of similar age/condition. Agree with others here. I had some boost related codes after going to MHD stg 1. Started with the low hanging fruit (vacuum lines). I'd replace stuff in order of least cost...replace the last two vacuum lines first (it's a PITA but doable by feel...especially if you know someone with small hands...I leveraged my 16 year old son... ). Then boost solenoids, then diverter valves. But before I did any of that, I'd look for oil sheen on the FMIC inlets/outlets and CP connections(see below).

I also ordered new boost solenoids but before they arrived, I replaced my FMIC this weekend. While doing so, I noticed oil film around the factory inlet connection. Turns out the gasket was leaking. I had already ordered new gaskets for the new FMIC so when I put it all back together...no issues (thus far..only one day in...but boost is now tracking boost target almost exactly while before, I was getting a boost "fade" at higher boost psi. And no codes) So, I probably didn't need to replace the vac lines...yet. But when I replaced them it was clear they were aged, so I am glad I did. Probably will put the boost solenoids on the shelf but based on what I have read, they are gonna go between 100-150K. Good luck!

[Jeff@TopGearSolutions]

Originally Posted by AndyW

My car is of similar age/condition. Agree with others here. I had some boost related codes after going to MHD stg 1. Started with the low hanging fruit (vacuum lines). I'd replace stuff in order of least cost...replace the last two vacuum lines first (it's a PITA but doable by feel...especially if you know someone with small hands...I leveraged my 16 year old son... ). Then boost solenoids, then diverter valves. But before I did any of that, I'd look for oil sheen on the FMIC inlets/outlets and CP connections(see below).

I also ordered new boost solenoids but before they arrived, I replaced my FMIC this weekend. While doing so, I noticed oil film around the factory inlet connection. Turns out the gasket was leaking. I had already ordered new gaskets for the new FMIC so when I put it all back together...no issues (thus far..only one day in...but boost is now tracking boost target almost exactly while before, I was getting a boost "fade" at higher boost psi. And no codes) So, I probably didn't need to replace the vac lines...yet. But when I replaced them it was clear they were aged, so I am glad I did. Probably will put the boost solenoids on the shelf but based on what I have read, they are gonna go between 100-150K. Good luck!

Great tips.

FYI you can keep that oil out of your intercooler and charge pipe with a Oil catch can.

[AndyW]

Originally Posted by Jeff@TopGearSolutions

Great tips.

FYI you can keep that oil out of your intercooler and charge pipe with a Oil catch can.

Yep..I've been running an OCC for about 5K now. Believe that other leakage on the fittings was residual.

[NightStalker]

Originally Posted by AndyW

My car is of similar age/condition. Agree with others here. I had some boost related codes after going to MHD stg 1. Started with the low hanging fruit (vacuum lines). I'd replace stuff in order of least cost...replace the last two vacuum lines first (it's a PITA but doable by feel...especially if you know someone with small hands...I leveraged my 16 year old son... ). Then boost solenoids, then diverter valves. But before I did any of that, I'd look for oil sheen on the FMIC inlets/outlets and CP connections(see below).

I also ordered new boost solenoids but before they arrived, I replaced my FMIC this weekend. While doing so, I noticed oil film around the factory inlet connection. Turns out the gasket was leaking. I had already ordered new gaskets for the new FMIC so when I put it all back together...no issues (thus far..only one day in...but boost is now tracking boost target almost exactly while before, I was getting a boost "fade" at higher boost psi. And no codes) So, I probably didn't need to replace the vac lines...yet. But when I replaced them it was clear they were aged, so I am glad I did. Probably will put the boost solenoids on the shelf but based on what I have read, they are gonna go between 100-150K. Good luck!

My boost selenoid got defective at mileage 42k before any tunes.