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e34 B10 Bi turbo won't boost above 1.1 bar?

12K views 39 replies 7 participants last post by  Bumbaclut 
#1 ·
Hi all,

I am having a random boost problem where sometimes you get in and drive and all is normal, other times it won't boost above 1.1/1.2 bar no matter the revs or where the boost switch is pointed. the engine itself is running as normal. I have had both turbos rebuilt and replaced the clutch but have had no electrical problems until now.

I have had the "EML" come on or flicker a few times also and my feeling is its suffering an electronic failure and as a safety net the boost is limited?

Thanks
 
#2 ·
Hello,,

A wild guess,, but there is a black plastic line that goes from the intake manifold,, under the T.B. in to the cable-slide and over the firewall direct in to the ECU box,, if this line is broken or cracked ,,this ,,,,,,,,,,,COULD,,,,,,,,,,,,,,, be the problem,, i had simelair issue and replaced the line with a new one,, be aware that the line plugs WELL in/on the little nipple that is on the ECU...:checkeredflag:
 
#3 ·
I had that problem with my BT (the cracked line issue) and it just stayed at 1.0 bar. When the condition occurs where it won't boost past 1.1/1.2 bar, does the car behave like it is not boosting like it does when things are working correctly? Or does it drive the same but the gauge doesn't seem to register the boost correctly?
 
#4 ·
hmmmm, the line looks fine to my eyes.

When it happens it drives like the boost is low, theres not alot of power. Well its very slow for a Bi turbo! The engine revs as freely as normal really, no smoke etc which leads me to think its an electronic fault of sorts
 
#5 ·
Hi, have you checked the boost LED above the boost adjuster? This LED should come on with the ignition and go off once the engine is running. If it comes on while the engine is running its an indicator that something is wrong with the boost system. I had this before and had help from Tomba regarding the TPS setup procedure. I've also had the manifold feedback pipe break and the readout is always 1.0 bar ( atmospheric ). I have since replaced this with the vacuum hose from the M5 intake.
 
#9 ·
Sticky wastegate? > Wastegate remains in an open position? How were the turbo's rebuild? Can't believe they replace the bushing and shaft from the turbine housing.

If the boost pressure on the VDO instrument cluster is 1,0bar @ engine off/ignition on and ~0.5bar @ idle the line should be ok. But please check the line completely by pressurizing it and topping it off at the end. Check for leak noises. The line should be routed towards the engine loom and can leak due to heat soaks or vibration at time.

Run the engine in 4th gear @ ~3000rpm to ~5000rpm full load. Long enough to let the LDR (LadeDruckRegeling) ECU to observe the boost pressure and set an error code. These ECU's are not that fast to diagnose errors.

The TPS could be faulty, not giving the right voltage to present the valve position to the ECU. But, this could be ignorred since the pressure that the turbo's would give without activating the "takt ventil" / N75 / turbo regulation valve, would ne near 1.4bar and above the pressure that you mention. Please use the search function or ask and have patience for the correct guide to adjust the TPS if you want to check it. I believe 310 +/-5 ohm @ WOT (ignition off, pedal to 100%, plug removed and measure pin 1-3 of the TPS).

Source the pressure line from the turbocharger actuators and pressurize it with air and check the wastegates for movement. It could be that you are not pressurizing them more than currently is possible (1.2-1.0[bar]=200[mbar]) and that they move beyond a sticking point in the bushing/shaft mechanism. This will put the wastegate valve to its "0" position once you pressurized them. Allready happened to me once on a BT. > in short; put pressure on the actuators of the turbo to move them open and remove pressure to see if they move to closing position. The line should be located under the air filter housing (3 lines towards an actuator/valve, if I remember correctly, W(astegate),R(ucklauf),C(ompressor). Use the W line.

This are the error/blink codes that could be present in the ECU.

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Blink codes Discription

3 1 boost pressure too low
3 2 boost pressure too high
3 3 pressure sensor in control unit defective
4 1 tension/voltage on the throttle potentiometer is defective/too low
4 2 tension/voltage on the throttle switch is to high - higher than 4,3V
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Accent 6"/> <w:LsdException Locked="false" Priority="67" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 1 Accent 6"/> <w:LsdException Locked="false" Priority="68" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 2 Accent 6"/> <w:LsdException Locked="false" Priority="69" SemiHidden="false" UnhideWhenUsed="false" Name="Medium Grid 3 Accent 6"/> <w:LsdException Locked="false" Priority="70" SemiHidden="false" UnhideWhenUsed="false" Name="Dark List Accent 6"/> <w:LsdException Locked="false" Priority="71" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Shading Accent 6"/> <w:LsdException Locked="false" Priority="72" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful List Accent 6"/> <w:LsdException Locked="false" Priority="73" SemiHidden="false" UnhideWhenUsed="false" Name="Colorful Grid Accent 6"/> <w:LsdException Locked="false" Priority="19" SemiHidden="false" UnhideWhenUsed="false" QFormat="true" Name="Subtle Emphasis"/> <w:LsdException 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mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} </style> <![endif]-->Since you are interfering EML issues it could be simple, the throttle valve is not opening completly and thus not giving the full power you demand. Is the EML lamp on when selecting ignition and than turning off? Are you able to measure voltages from that ECU?

I measured a lot values in the past while driving the BT. We can compare these values to yours. They should be similar.

Please make videos to show us what you are observe during the phenomena. Makes it much easier for us to diagnose a problem.
 
#10 ·
Thankyou for that detailed reply!

I've currently made no progress as i've been working 6-7 days a week and its not given me the time this car needs :grrrr:

The interior is not fitted and i have the carpet out of her at the moment drying out after tracing several leaks!

From playing with the car i've looked at the TPS switch and i can hear it "clicking" still which is a good sign. With the ignition on i can see the Throttle body opening when you press the accelerator with the engine running. ITs nothing detailed i know but made me think the problem was elsewhere

The turbos were rebuilt completely, on the rear one the turbine spindle snapped, so its as new. The front is also. They were rebuilt back to standard spec. The only thing i had changed was 360 degree thrust washers fitted. They advised to keep the boost standard as they work hard on Bi turbos as they are! The wastegates where checked and deemed working fine.

My turbos had been rebuilt before here in the UK, but i have no receipt for the cars records. So they have been rebuilt twice in the cars life, the milege is 196,000kms

I shall get the spanners out over christmas and get checking wastgate and other boost lines you mention
 
#11 ·
i've finally had a bit of time to have a look and the guage reads 1.0 bar with the ignition ON, then drops to 0.5bar @idle. The boost LED is on with the ignition and goes out when the engine fires.

However if you rev it, ( i cant drive it as the interior is removed at the moment) then the EML light is coming on, then when switched off it stays on. I need to have a better check i think possibly of the TPS as you mention Tomba and check the resistance against the one given.
 
#13 ·
You could have a defective cluster I had spent a year going back an forth with Alpina replacing throttle body and computers and still could not get the car to boost, all the test and check Alpina had me verify all came back ok. I read on a post of some one who had a 535I with eml could not get the car to run properly. I finally went to the junk yard and got a standard 535i cluster remove my Alpina one and install it following Alpina instructions to reset the EML and throttle body and wow now the car run like a dream. I was able to pick one up at the junk yard for $35 If every thing runs properly simply just swap out the Alpina speedo and matching gauge and you should be fine. In my opinion it is worth a try. I spent all together 3 there to finally get #384 running like it should. Good luck.
 
#14 ·
hmmmm just reading online and i may not have mentioned but when its playing up the cruise control wouldn't work. I'm starting to suspect it could be an EML fault.

I've tried looking for some pictures of someone taking the unit apart like Bud suggested but have drawn a blank so far. Most people seem to end up swapping clusters about like tunderbolt suggests. I don't have a spare cluster to try but i could get one. Saying this 6 cylinder cars with EML fitted this side of the pond were very rare as only the cars specced with traction got it. I'm sure it wasn't standard on our 535's in the UK.
 
#16 ·
The one I use was a 535i with out EML I guess BMW employ the EML in all its cluster. just make sure the one you get has the EML window on the gauge face. I would do this before messing around trying to rebuild the throttle body. I had end purchasing a new throttle body from BMW and it never resolve my problem save yourself the headache.
 
#17 ·
Right i've done a little vid to show whats going on i've just got to work out how to upload it onto youtube or something. From what i can see notice now is that the throttle isn't fully opening, well hardly at all even with the pedal pressed flat it barely opens. Enough to rev the engine but thats it, so i guess thats why there isn't alot of power when driving? Just need to work out why its not functioning properly. It opens and shut easily i would say if i use my hand
 
#18 ·
Ally of what you are experiencing are the same symptoms I had, save yourself a lot of time, headache and money and replace your cluster it took me almost three years and lot of money to get #384 running. If you know anyone with a 535I ask to borrow the cluster install it and see what happen. Good luck
 
#19 ·
Try to get the error codes from the EML first before buying parts. That should guide you in a direction with the faulty part.

Most of the problems with EML that I see are the throttle valve electronics. The one for the M30 engine is hard to get but the M70 (V12) not.
And the best is that the electronics (resistor track, wiper, plug/connection) from the M30 throttle valve is identical to those from the M70.
Get a M70 throttle valve, remove the electronics, refurbish the M30 mechnical parts and put back the M70 electronics. !!! mark the wiper location or measure the resistance of the wiper track at closed throttle to make sure they are within specification!!!

http://www.m5board.com/vbulletin/al...69-how-rebuild-your-throttle-bodies-long.html
 
#22 ·
well it worked but then it didn't so it must be something else that controls the throttle body itself. So am i right in assuming there is a part within the instruments thats to do with EML. I've got a friend who might have a cluster i can try from a 535i i shall ring tomorrow
 
#26 ·


I did clean everything up and the brushes move freely now




This to me looks in perfect condition compared to the pictures on car #260's thread




Now should these brushes which make contact with the disc shown above be different? i guess they should all be in line as such?! I'm going to straighten them all out and try it all again as looking at these it makes me think. If all the brushes are not making contact it won't function properly in my mind hence it only opening a little bit as not all brushes in are in contact to give the correct signal
 
#27 ·
Now should these brushes which make contact with the disc shown above be different? i guess they should all be in line as such?! I'm going to straighten them all out and try it all again as looking at these it makes me think. If all the brushes are not making contact it won't function properly in my mind hence it only opening a little bit as not all brushes in are in contact to give the correct signal
Yes they should, your brushes don't look good. I suspect a lack of tension to the disc makes the error.
 
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