Lack of low speed power, CTD 2.0 ltr
 

Evening all, just bought a one owner 75 tourer with 122k mls on it. Came with a hot start problem (was aware of this) which with the help of searches on this excellent forum was traced to very bad leakback on no4 injector. Injector replaced (came out very easily) now starts perfectly hot or cold. So far, so good. Took the car out for its first decent run today only to find that it seems to lack any power until about 2000rpm. This I assume is when the turbo gets going. But up to then it seems very lacking in power to the extent that it difficult to drive, having to constantly use the gears to keep it spinning away. A basic test on the run showed that on a flat road with it running at 1500rpm in 5th gear no acceleration at all was possible. In 4th gear, it would very slowly accelerate until it reached 2000rpm and then get going apparently ok. In lower gears, dead until 2000, then away it goes easily passing the 4000rpm mark. The car was chipped from new to ZT spec. Any ideas please. Have only covered 50 miles with the car, the re-set computer says 44mpg.

Probably you need a new Mass Air Flow (MAF) sensor. That would account for sluggish performance below 2000rpm. Look on here for the thread about the £75 MAF. That's your answer.

Diesels need revs, give the car some welly and it will go like a goodun innit..

Pussyfoot about with it and it will drive like a hearse on a rainy day... :shrug:
...

I know what you are saying gov, but I am well used to diesels, drive the all the time. I am afraid this one is seriously lacking in the low speed (revs) dept.

Definitely the MAF sensor, (Mass Airflow Sensor).
Quick fix to 100% prove is to simply disconnect and your car will be transformed.
Some on here leave them disconnected, no detriment to the car that I know of, excepting prob wont get optimum power and fuel economy.
Then in slow time you can work out whether to replace with another Bosch MAF, mixed reports on here how long they last, I went for the RonBox Synergy II with piefberg MAF, gives extra power and better fuel economy for about same money.
Sure people will soon comment on other options as have seen quite a few of late.
To disconnect MAF remove big engine cover first one with BMW embossed on it.
Then remove remaining cover, the one the oil filler cap is part of, and where air filter sits beneath.
The MAF sensor and plug just to left of filler cap, you will need to mess with clips either side of black plug and the connector should pull free, stash connector safely somewhere in that area and have a drive, let us know how you get on.
Take care
Steve

Yes, should have mentioned disconnecting, easy test to see if it is the MAF, rather than buying a new one on spec. But it will be, I bet!

Thanks for that. Previous owner claimed to have replaced it when trying to cure hot start problem but still worth a look.

Thanks Steve. I will follow yours and Johnny's advice and try it with the MAF disconnected. As reply to Johnny, previous owner said he had replaced it but also mumbled about shopping around for the cheapest so maybe he fitted a duffer.

Should also have said that the engine seems fine otherwise, no smoke or nasty noises. Came with full service history and I am very pleased with it, just need to sort this low power issue.

Sorry guys, but £75 is still a lot of money to spend on the off chance it will fix the issue, nor does disconnecting it prove it is really at fault.

If you think it might be the cause, simply test it using a basic diagnostic unit against the figures we have determined, it should read at tick over and 3000rpm in the recent thread.

There are many potential causes of these symptoms, other than the MAF and just chucking money at it in replacing parts is doomed to be an expensive solution.