Hi All

I recently purchased a BMW 120D and i'm having a difficult to diagnose problem. Wondering if there is any super knowledgeable BMW guy out there that could give me some advice

It randomly seems to lose power drastically, you would pull away and put the throttle right to the floor and nothing would happen, the car would move like it had 3bhp. However if you let off the throttle and back on it would launch into life and go off like a rocket. it would do the same thing in 2nd and 3rd

I have had it read on a BMW ISTA machine and it came up with loads of fault codes pointing at MAF, DPF and EGR and high exhaust pressure. I had the DPF removed and the EGR cleaned with crossed fingers and picked the car up today. It has no more reappearing fault codes but it has not removed the problem. It is a lot better but still has the same problem. It seems like if you put the gas on hard when the RPM is under 1800 it wont go but if you put it on hard after 1800 its fine

The garage have said sorry thought it was the DPF next try changing the turbo!

Its already cost me £400 and a new turbo would be another £1500 also the turbo was only replaced 4 months ago!!!

By my knowlegde the turbo is making no funny noises the car is not smoking and it works perfectly most of the time so I am reluctant to fork out the money on a mechanics hunch that he wont back up with any guarantee that it will fix the problem

I have been googling for hours and am no closer to an answer

Any advice would be massively appreciated

Thanks

Dave

What type of engine do you have? Is it a M47N2 (163 bhp), or maybe the newer N47 (177 bhp)? All 120d engines have a turbo lag, which is present up to around 1800 RPM. That's totally normal on the stock car.

If you want to remedy this, you can remap the ECU using a custom map. This will increase total power (depending on the level of performance you need) up to 205 bhp and if the map is done right, it'll reduce the turbo lag, so you'll be able to use the torque sooner than from 1800 RPM.

Keep in mind that all turbocharged engines lag a bit, though in case of modern diesels it's not as bad as the lag Subaru's or Evo's get.

I figured it out last night. With the blocked dpf it filled the turbo with carbon and it built up behind the actuator arm so much so it would move freely, stripped and cleaned the turbo and it's now fine

Thanks anyway

Hi Budro

My 120d is doing exactly this. How easy is it to clean the turbo?

Thanks

Dan

It's not that difficult, it's all accessible from the top. Before you take it apart you can check that this is the issue by revving the engine whilst checking that the actuator on the side of the turbo is moving.

Feel free to PM me your number if you want me to go through it with you

this sounds interested, I have a 118d and I have noticed very similar symptoms to what you descried, especially a lot of lag when setting off from around 1500ish rpm.