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2001 E46 320d, flat patches in power, turbo lag?

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8K views 12 replies 6 participants last post by  gav869 
#1 ·
Can anyone help, i have recently bought a 2001 320d. the car runs well but there are flat patches in the power delivery where aceleration is slow until the turbo kicks in where it then suddenly gets its power. i also seem to have to change down gears more than i should need to whilst driving, for instance if im on the motorway driving at 70 in 5th gear and i have to slow down to say 60 when i put my foot back down the turbo doesnt seem to kick in and i have no aceleration. this happens through all gears at different speeds. whats wrong???
 
#4 ·
There are four likley culprits for this, as Ronnie rightly pointed out the MAF sensor but it could also be the MAP sensor which measures boost pressure, a clogged EGR valve or the vacuum hoses to the Turbo vacuum reservoir and then to the turbo.

The best way to get to the bottom of the problem is to get the fault codes out but there are some jobs that can easily and cheaply be done.

Have you taken the swirl flaps out? that is critical on a car of your year, if they brake off which they often do, it is curtains for your engine.

To get to the MAF sensor you need to take the engine cover off (5 x 5mm allen screws) and then on the left hand side you will see the air filter housing and infront of that a black oval tube with a connector on it, unplug that and try driving the car. It won't run great but it might run better if your MAF is dead.

Cleaning the EGR is a must and changing the vacuum house just requires 2 meters of 3.5 silicon vaccum hose which should cost no more than a fiver.

There are some great pictorial guides on this forum for all the tasks described above, the search facility will help you find them
 
#6 ·
Have a look on your V5 and see what the engine CC is listed as, if it is 1951 then you have the M47, if it is 1995 then you have the M47N. :)

Otherwise look on your chassis plate which is in the engine bay either on the inner wing or just behind the headlight, on the left of the chassis plate it will say the engine code.
M47 = 204D1.
M47N = 204D4.
 
#7 ·
hi guys
thanks for all the help. ive now changed the maf sensor and i have loads more power, it slightly drops around 70 but then boosts back up but judging by the whistling noise coming from the turbo im guessing i need to change the gasket which ive heard is a massive job.
ahh the joys of owning a bimmer lol
 
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