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320d intermittent loss of boost

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My 2003 e46 320d m47 Touring has been suffering from a very intermittent turbo boost issue. It's only happened a couple of times in the last 1000 miles. Basically I'm driving along and all of a sudden I go into a limp home mode, I have no boost, no errors on the dash and no matter how hard I put my foot down the instant MPG gauge doesn't drop like it usually does. As soon as I turn the ignition off and back on we're back to normal. The car has done 140k and I've done 60k of that. Serviced as per the indicator thing, driven quite hard and swirl flaps were done 30k ago. 

I had the codes read today on an Autologic A020691 BMW v3.153.0, Main v6.6.0: 

DDE d50m47b1
2 Faults
4191 Charge-air pressure actuator activation
4521 Charge-air pressure control, control deviation

The garage also did a boost pressure test, see attached pic, and said that all looks ok. There suggestion is a new turbo even though they think it's likely to be the electronic actuator.

Any thoughts please?

It's shameful to admit it but I recently bought a caravan and will be towing it around for the next 3 weeks through some hilly terrain so can't afford to be down on power, especially with wife and baby in the car. I should add that I have lost boost once while towing, only towed twice, but that the problems started before the caravan!

I'm based in Staffordshire.



IMAG1253 - Copy.jpg

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Is it defo an electronic actuator on your turbo? Some, mine included, is a vacuum actuated one, but with an electronic controller to adjust the vacuum. 

Does sound like it's likely to be the boost control though from that. Its well worth buying inpa for £20-30 and doing your own testing while driving around. 

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Thanks for the advice TriggerFish.

Since posting I've had no more boost issues and done 1700 miles on holiday, towing the caravan for more than 1000 of that😀

Fingers crossed things will continue this way!

Next job is to sort the rather tired suspension and get the 4 wheel tracking done. Car and caravan weren't as stable as I'd like. Had a massive snake 8 miles into the holiday trip😱



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Not as long as the snake of cars behind you!

lol. I'd of thought that as a novice they would of had traffic warning out for me but it was generally trucks and old people slowing me down! If there are people behind me and I see a chance for them to get by I indicate left but it's surprising how many people seem happy to follow! I know I wouldn't😉

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Hi Gerg 

I too once had an intermittent turbo boost issue. Its really annoying isn't it! 

It took me years to find! I was of the mentality of "fix it once it broke" as i couldn't for the life of me find it. It never broken, but i'm pleased to say i found it & fixed it!

I also straight away got it plugged in at a garage, and they said looked like actuator issue, mines the electronic one.

The PC did come up with faults for the actuator, but once cleared, ran and retested no fault codes. Even though the fault kept occurring.

From my years of looking (on & off because I'm lazy as) here's my advice in fault finding this issue. I recommend doing it in the same order (easiest/ cheapest first);

Note; remove the plastic engine cover and leave it off until the problem(s) found.

1.) unplug the MAF sensor and take the car for a spin if the fault stop occurring, plug it back in and see if it comes back, if it does, unplug again and see if it stops again. This will prove if its the MAF. (Don't worry about the engine light, it goes off once plugged back in, left for a while and engine re-started.)

2.) unplug the fuel temp sensor, again drive without it and see if this cure's the issue. (this will leave a fault code on the ECU, which can be cleared, but don't worry about it.)

3.) Unplug the 4mm vacuum tube to the EGR, insert a 4mm bolt (or golf tee) in the open end of the tube and cable tie the tube tight around the bolt to stop it falling off. Take the car for a spin and see if the issue stops.

4.) Buy a can of electrical contractor spray (about £3/£4), pop the bonnet with the car running and start spraying every air hose to try find if any are slightly spilt. The engine RPM will drop or the engine will shudder when your spray any spilt hose(s). Replace where required. Check your service book for something like "breather filter" it will be penned in if BMW have done it in the past.

5.) replace all the 4mm vacuum tubes. Its not that expensive (about £20 off ebay) and see if the problem stops. I noticed a performance increase once swapped! You will have to take the inlet manifold off, so you might as well service the air filter and give the EGR a clean. If you haven't changed the crank case ventilation filter for the voxtec one you need too! Do this while changing the air filter. If it is a vortex crank case breather filter, don't bother changing it their a fit and forget item.

6.) Jack the car up and remove the inter-cooler (its really not that hard and can be done in 30 mins), once removed put the inter-cooler on a dry floor with the inlet/ outlet ducts pointing up. Now fill the inter-cooler with water to see if there's any leaks. If it leaks swap for a new one (about £100 for Andrew pages etc.) If the cooler turns out to be o.k. let it dry out first before re-fitting, it might not cause an issue, but better safe than sorry!

7.) Buy a new MAP sensor and replace it on the inlet manifold. There about £50 from BMW. really easy to change. Again see if the problem stops. You cant unplug this sensor and take the car for a spin because it goes into limb mode (mine does anyway, worth trying before buying a new one).

8.) Buy a new diesel priming pump. This is the pump under the middle of the car, roughly behind the hand brake. There about £120 and easy enough to fit yourself. This pump might be whats called "soft failing".

9.) Buy a new vacuum pressure converter. this is located under the inlet manifold, and is the unit all the 4mm tubes for the EGR runs to. Or try fixing it yourself, this video shows you how to do it; 


 (note i never had to do this because i found my fault, so i can't recommend the DIY fix)

I believe there about £120 for a new one.

10.) Start worrying as you may need to start looking at a new turbo, high pressure fuel pump, or injectors etc.


That's all i know i'm afraid, mine turned out to be the inter-cooler. But i have done all the tests above excluding steps 9. I did step 10 a lot!

One thing i need to ask, have you had your swirl flaps blanked off? if you haven't, that would be the first job i did, that along with replacing the crank case breather filter! Once the inlet manifold's off (which isn't a hard job at all) its an easy DIY job to do. Might be worth re-placing the inlet manifold rubber gaskets while your there.

Let me know how you get on.

Any questions please don't hesitate to ask?




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One more thing i meant to say, if the problem goes away when the EGR is unplugged, try cleaning it first before buying a new one;

Again if its the MAF, try cleaning first before buying a new one. If you have an aftermarket air filter, the ones you re-use and oli, its probably the MAF all grudded up.

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