[Unai]

Hi guys,

I bought a used 335i some months ago and I've had problems since the first day. The car has hybrid turbos, DCI, downpipes and a remap to 417hp (probably MHD).

The car boosts fine when it's cold (90 degrees celsius) but when it is fully hot (120°) the car just doesn't build any boost. It is most evident cruising highway at 6th gear, if I press the pedal strongly the turbo doesn't whistle at all and the car accelerates very slowly. If I keep pressing the car enters limp mode with a 30ff error.

I took it to a BMW specialist and they made vaccuum test without apparent air leaks (I think they made them in cold engine) and they asked me if I wanted to dismount the turbos to check them... But I am not ready yet.

What do you guys think could be the issue? Some people say it could be the solenoids, but they were supposedly replaced by the previous owner. Another possibility could be the wastegates, but I'm not sure if temperature could affect so much to any of those elements.

Any help would be so appreciated. Regards!


SOLUTION after 2 years:

I discovered that my car had a JB4 installed in Map 0 which was causing signal interruptions. I removed it some days ago and since then my car is working fine. No matter how long I drive, it never has turbo lag or 30ff codes.

Aside from that, I also had some crankshaft sensor shadow codes (2FDA, 2FDB), that became worse some weeks ago with a full error (2A94) that caused Limp Mode and ECU malfunction. So I also changed this sensor.

This thread helped me a lot to diagnose the problem:
https://www.e90post.com/forums/showthread.php?t=1668852

So, after 2 years of headaches, hundreds of hours of reading forums, and some money wasted in tests, I have finally fixed this damn car and can enjoy it fully

[RayLivingston]

Hard to imagine what, other than something related to the wastegates, or badly damaged turbos, could possibly induce a complete lack of boost. Since they work ok cold, that pretty much rules out damaged turbos. I would start by closely examining the wastegates, and all the associated solenoid valves and vacuum lines. Again, since it all works cold, that is all likely ok, but check it all out just to make sure

Next place I'd look is the two intake pressure pressure sensors. One of them also contains a temperature sensor used for sensing intake air temperature. The boost pressure sensor, mounted on top of the intake air duct right under the air filter box, is (only!) about a $100 part, and very easy to replace. The manifold pressure sensor is top of the intake manifold itself, also under the air filter box. Might be worth swapping out both, just to rule them out. I found a new-in-box factory boost pressure sensor on EBay for ~$90, and the manifold pressure sensor for only $20.

Regards,
Ray L.

[Unai]

Originally Posted by RayLivingston

Hard to imagine what, other than something related to the wastegates, or badly damaged turbos, could possibly induce a complete lack of boost. Since they work ok cold, that pretty much rules out damaged turbos. I would start by closely examining the wastegates, and all the associated solenoid valves and vacuum lines. Again, since it all works cold, that is all likely ok, but check it all out just to make sure

Next place I'd look is the two intake pressure pressure sensors. One of them also contains a temperature sensor used for sensing intake air temperature. The boost pressure sensor, mounted on top of the intake air duct right under the air filter box, is (only!) about a $100 part, and very easy to replace. The manifold pressure sensor is top of the intake manifold itself, also under the air filter box. Might be worth swapping out both, just to rule them out. I found a new-in-box factory boost pressure sensor on EBay for ~$90, and the manifold pressure sensor for only $20.

Regards,
Ray L.

Thanks for your answer Ray! I will keep this info in mind and check it out next time I visit the mechanic

[iqraceworks]

After the car is hot....hook a vacuum pump (mighty vac) to each wastegate and pull a vacuum on them....make sure they are moving the wategate arms, and not binding. Also make sure they hold vacuum. That's where I would start.

Also check vacuum lines, and connections at the intercooler and charge pipe when everything is hot.

That's where I would start.

[Unai]

Originally Posted by iqraceworks

After the car is hot....hook a vacuum pump (mighty vac) to each wastegate and pull a vacuum on them....make sure they are moving the wategate arms, and not binding. Also make sure they hold vacuum. That's where I would start.

Also check vacuum lines, and connections at the intercooler and charge pipe when everything is hot.

That's where I would start.

Thank you, I will tell the mechanic to try this, too. Is it necessary to pull out the turbos in order to check the wastegates?

[iqraceworks]

Originally Posted by Unai

Thank you, I will tell the mechanic to try this, too. Is it necessary to pull out the turbos in order to check the wastegates?

No, you can look down on the passenger side and see the rear one.......with a small mirror, you can see the wastegate on the front one.

[Unai]

Btw, I forgot to mention mi turbos are hybrid! Could it be that they are defective?

[dpaul]

Originally Posted by Unai

Btw, I forgot to mention mi turbos are hybrid! Could it be that they are defective?

Since you say that boost is normal when the engine is cooler, it is unlikely that there is anything wrong with the turbos.

You mentioned 30FF - are any other codes also reported by your DME?

[Unai]

Originally Posted by dpaul

Since you say that boost is normal when the engine is cooler, it is unlikely that there is anything wrong with the turbos.

You mentioned 30FF - are any other codes also reported by your DME?

No man, 30ff is the only code that appears. It is like the turbos are not even receiving the order to build boost, since I can't hear any turbo noise.

[dpaul]

Originally Posted by Unai

No man, 30ff is the only code that appears. It is like the turbos are not even receiving the order to build boost, since I can't hear any turbo noise.

Then the suggestion of vacuum leak is likely correct. Of course, full diagnosis is made more difficult by fact that it is apparently temperature dependent.

The simplest and most likely point of vacuum failure are the hoses. There are a lot of them - connecting the engine-driven vacuum pump to the cannisters, connecting the cannisters to the solenoid valves and connecting the solenoids to the wastegate actuators.

Start by replacing all of those hoses, including the hard lines that go over the valve cover. This is pretty cheap and easy. If that doesn't solve the problem, you can think about the other components that have been mentioned. But it is ridiculous to suggest removing the turbos for inspection - try a different BMW specialist next time.

[Unai]

Originally Posted by dpaul

Then the suggestion of vacuum leak is likely correct. Of course, full diagnosis is made more difficult by fact that it is apparently temperature dependent.

The simplest and most likely point of vacuum failure are the hoses. There are a lot of them - connecting the engine-driven vacuum pump to the cannisters, connecting the cannisters to the solenoid valves and connecting the solenoids to the wastegate actuators.

Start by replacing all of those hoses, including the hard lines that go over the valve cover. This is pretty cheap and easy. If that doesn't solve the problem, you can think about the other components that have been mentioned. But it is ridiculous to suggest removing the turbos for inspection - try a different BMW specialist next time.

Well the funny thing is that I called another BMW specialist and when I told him that the turbos are hybrid and the issue happens when the engine is hot... "the best thing would be to revert the car to stock and check those hybrid turbos" goddammit

[Unai]

Some people suggest me making a log with MHD (which I would need to buy). Do you think it would help diagnosing the problem?

[dpaul]

Originally Posted by Unai

Some people suggest me making a log with MHD (which I would need to buy). Do you think it would help diagnosing the problem?

Can't hurt but I don't think it will necessarily tell you more than you already know - that the boost stops when the engine gets hot.

However, you'll want to log once you deal with the mechanical problem to verify that things are working correctly. Any time modifications are made to the engine logging is important.

[Unai]

Do you think that it could be an obstruction somewhere? Like the downpipes, a piston, whatever...

[dpaul]

Originally Posted by Unai

Do you think that it could be an obstruction somewhere? Like the downpipes, a piston, whatever...

No.

Test vacuum hoses, boost solenoids and wastegate actuators when the engine is hot. Just first address the simple possibilities, which have already been discussed.

[Unai]

Originally Posted by dpaul

No.

Test vacuum hoses, boost solenoids and wastegate actuators when the engine is hot. Just first address the simple possibilities, which have already been discussed.

Allright, until 22th I don't have the appointment with the mechanic so I'll keep you posted.

[NoGuru]

When rubber hoses are cold, they are more ridged. Once these heat up they can do two things, one is expand easier and two they can collapse easier.
I would check all soft or rubber connections if you say it is only when things heat up.

[iqraceworks]

Originally Posted by dpaul

No.

Test vacuum hoses, boost solenoids and wastegate actuators when the engine is hot. Just first address the simple possibilities, which have already been discussed.

This. You could be getting a leak when something gets hot.....just go through one things at a time, testing it.

[Unai]

Originally Posted by RayLivingston

Hard to imagine what, other than something related to the wastegates, or badly damaged turbos, could possibly induce a complete lack of boost. Since they work ok cold, that pretty much rules out damaged turbos. I would start by closely examining the wastegates, and all the associated solenoid valves and vacuum lines. Again, since it all works cold, that is all likely ok, but check it all out just to make sure

Next place I'd look is the two intake pressure pressure sensors. One of them also contains a temperature sensor used for sensing intake air temperature. The boost pressure sensor, mounted on top of the intake air duct right under the air filter box, is (only!) about a $100 part, and very easy to replace. The manifold pressure sensor is top of the intake manifold itself, also under the air filter box. Might be worth swapping out both, just to rule them out. I found a new-in-box factory boost pressure sensor on EBay for ~$90, and the manifold pressure sensor for only $20.

Regards,
Ray L.

Hey Ray, I brought the car to the dealer, and guess what... It popped out an error of the turbo sensor, the one you mention it's under the air filter box! The error was permanent, it didn't get away after restarting. He put it out and in again and the error disappeared. I went for a test drive at 120° and the turbos were spooling all the time, without errors or anything.

I'm not sure if the issue was that sensor or that the environment temperature is now way colder than in summer, but the issue seems fixed. If I get the error again I'll just put a new sensor!

I'll keep you updated if the issue is permanently fixed!

[Unai]

Hey guys, I've test driven the car and after an hour I ended up getting the 30ff error, but I noticed some things:

It has happened in 4th gear, accelerating from 2000 rpm. I noticed that the turbos weren't spooling at all, I couldn't hear any pssss noise. I kept pressing the accelerator until the Limp mode came up. I kept accelerating and after 4000 rpm the turbo activated suddenly. Even with limp mode active the turbos were working, I don't understand.

So to sum up, the problem happens with hot engine after driving a while, and it only happens sometimes, like something gets stuck.

Do you think that it could be that the wastegate was open? If it's open would the turbos spool? Could it be that the boost pressure sensor is indeed wrong and it fails sometimes?

[relative4]

Are you getting any codes for the water pump or fan? What is your oil temp? And your coolant temp?

[Unai]

Originally Posted by relative4

Are you getting any codes for the water pump or fan? What is your oil temp? And your coolant temp?

The only code is 30FF last times I checked. I don't know today.

The oil temp is around 120° celsius. I don't know the coolant temp.