Engine Performance problem
2004 BMW 320 4 cyl Two Wheel Drive Manual 107000 miles
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My 3 series 2.0td has an intermittent problem when accelerating. It sometimes stutters as though it needs time to think what it needs to do and then it goes like a bat out of hell! Any time engine under stress, ie going up hill it really struggles to get going, your foot could be to the floor and yet it won't accelerate! Diagnostics indicated airflow problem.

I changed airflow meter, local bmw garage now wants to change turbo, a turbo specialist says turbo is fine and now third garage says its either a map sensor or ecu!

Hi jmt1,

After replacement of air flow was diagnostic done again? Does it show same code?

Did you check the wire connectors or circuits?

Yes when air flow meter replaced a further diagnostic was done and it was supposed to be clear. I did not check wiring.
A point to note is that the fault appears to get worse as the car gets warmer! When cold it appears surprisingly ok!!
BMW error code P3263 comes up now wehn a diagnostic machine is plugged into the car.

Hi jmt1,

Sorry to say that I am not able to get any info on the code you mentioned.

Since the problem is more prominent after warming up engine, I would suspect it to be a bad connection somewhere, maybe the MAF or other connectors. Check for contaminations or corrosion among all the sensors sockets.

Just returned from garage that used two diagnostic machines on it. Both say boost on turbo ok (1.0 bar I think the mechanic said) although there is an oil leak from it which looks to have been leaking for a while. Rest of settings ok apart from battery that reads 30 (ish) volts! Strange?

Electrics have been checked and seem ok!

Have changed middle cat exhaust but situation actually worse now. Fault continuous now except where car left to stand for few days then ok for a while! Car really strugggles below 2500rpm when warm especially when under more pressure such as going uphill. Once above those rpm the turbo kicks in and the car flies! Two mechanics looked at it today and are confused!

Hi jmt1,

The next tihing I can think of is the fuel pump and injectors.

But the voltage is something you need to check out, there ought to be somethng wrong with the charging system.

According to my friend who used two diagnostic machines everything is operating as it should!

Is it possible that when hot the turbo could stick when at lower revs and as such it needs more pressure to get it running? Hence poor performance at low revs? Could this be a result of poor lubrication as there is a very small leak of oil from the turbo.

The BMW dealership say it is the turbo and want to replace that first!

Hi jmt1,

I would rate it as very unlikely, whereas the opposite would be morel likely, when cold it sticks and when hot it would run better.

What I mean is the fuel pump might not be supplying proper fuel pressure/volume at lower rpms thsu the lack of power at low rpms only.