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Discussion Starter #1
I bought my 320d a few weeks back now with the knowledge that it had a boost issue and a few other little niggles that’s needed sorting.

The syptoms i am getting seem to vary every time I drive it. Mainly in first gear WOT I rarely get boost, and if I do it kicks in around 2200rpm. When I don’t get boost and shift into second, again WOT, I won’t get boost in second either until I lift an re apply. Sometimes happens when cruising along and I put my foot all the way down then again this can be cured by simply lifting off and re applying the accelerator. In the higher gears I can sometimes feel the boost dropping off during WOT and if I keep it planted I end up in limp mode, which is cured by flicking the key off and back on..

So far to try and solve this I have -

- Blanked off the EGR - also tried the old EGR cleaned up before..

- Checked the vac lines for any leaks, have ordered some pipe to replace them all anyway it’s just bringing myself to remove the intake again.

- replaced the electronic turbo actuator

- replaced MAP sensor

- unplugged maf sensor, I do have another maf but my understanding was that if it ran better without the maf then this was a clear indication that its faulty, which mine remains the same.

- cleaned plug connectors

The codes I am getting are

4191 - turbine control flap activation

3F00 - Charge air pressure signal

4521 - Charge air pressure control small turbo control deviation.

After doing some runs I realised that the actual boost compared the the desired boost was way higher, at this point I swapped the turbo actuator and this seemed to come back into spec. But the air pressure seemed to be higher than desired all the time, except for idle. Im under the impression that the car has been remapped in the past as the desired boost Pressure is 2400mbar (35psi) rather than the standard 22psi (I think?)

When the car is having a good day it’s great, holds boost well and shifts like it should. It’s still very drivable on its off days but like I said you have to come off and back on the throttle to see boost.

My other half drives it round and tells me it’s fine and I don’t drive the car round flat out everywhere but I know this there is an issue so I’m constanly testing the car to try and narrow it down.

Any advice would be appreciated as I’m pulling my hair out trying to find this problem and have got to the point where I’m chasing my tail a bit!

A pic of the new work horse and older brother!
 

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Discussion Starter #2
...Tumbleweed...

So after researching a lot about various boost issues I have come to the conclusion that I either have a vac leak or an actual boost leak which isn’t large enough to shut the boost off completely at times but the sensors and actuators don’t respond aswell depending on how I apply the throttle ect.. plan is to replace all the vacuum hoses this weekend.. I’ve ordered a PCV although on real oem I seem to only get the vacuum operated turbo diagram so once the manifold is off I can investigate further on where this valve routes too. Going to remove the intercooler pipes + intercooler and check for any damage/wear that could indicate why I’m having these intermittent issues.

Turbo seems fine, maf has now been swapped for the new one, now I’ve read online about coding these maf’s to the earlier models.. as mine is a 54 I was under the impression I don’t need to do this? I simply reset the adaptions and the car carried on acting like a d**k as it has been since owning it.

Also got to change the wheel bearing this weekend and the wishbone bushes so all in all a fun packed weekend trying to fix this lovely example of a bmw

Any advice, personal experiences relating to the boost issue would be greatly appreciated!
 

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Replaced vac lines today, replaced the PCV and the power delivery seems to be a lot smoother, checked the intercooler for leaks whilst I was doing the lollipop bushes, broke a clip as I was removing the intercooler so it pops off eventually.

Going to replace the the intercooler clip and take it on some proper runs.

Could only get the car to play up once, in second slowing and then WOT and then the boost pipe popped off, which leads me to believe that even though I was under the impression I had no boost, clearly I had boost to pop the cooler piping off.. now starting to think maybe it’s fuel, although the actual and desired figures I was getting on my Ethos seemed to be spot on?

Also..removed the MAF piping to the turbo, the seal seems to fit fairly loose. Refitted it and built the engine back up but seem to have an actual boost leak now as there is a definite hissing noise.. clearly something I have done but it definetly wasn’t there before although the car seems to be behaving better... maybe when I track the hissing down and sort the intercooler clip I may some luck.. seem to be chasing my tail!

Car handles a lot better with the polybushed bottom arms now.. do recommend them!

Any help pointing me in the right direction would be much appreciated!
 

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New seals and clips + lower piping on the intake and turbo side ordered. Had soot around the intercooler ends and pipes seemed to be loose so I’m guessing I may have found my problem. Also whilst the intercooler was off I lay it on its face and filled it with water to see if I had any leaks on that, was all good but I have heard of this being a problem on some.. worth a try as the intercooler comes off with ease.

Will update if the problem is fixed to hopefully help anyone with the same issues along with step by step of what I did, cheapest to most expensive tracking down this issue.
 

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Fitted new pipes + seals + clips.. still not correct, better but not how it should. Rang up an old friend who is also a bmw specialist and worked on a few of my cars and he asked what MAP sensor I used and by any chance was it FIA.. yes it was and he told me to scrap it and get a bmw genuine one which only turned out to be £10 more than the FIA in the first place.. £62.

Car runs absolutely perfect now boosting in all gears WOT and from stand still the car feels perfect. I’m going to change the turbo actuator back over for the original as this clearly wasn’t the issue.. considering the MAP is one of the first think I changed it seemed to just remask the issue leaking me to change everything but the map.

Thanks for all the help and advice.. till next time?
 
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