Poor performance issue finally resolved??
This might help anyone with poor performance issues with their R56 Cooper S\JCW.....
I've just booked my JCW (2008) in to an independent BMW specialist to investigate an on going problem since I bought the car 15mths ago.
It's never really run smoothly particularly when changing through the gears, (it seems to lurch in to gear 2nd-3rd), and sometimes hesitates for a split second under acceleration.
So the history looks like this...
I took it to one independent garage a few months ago to check this out, and they reckoned there was an air leak under boost. They did a smoke test, and the test showed no air leaks, but the mechanic mentioned for a JCW, the car didn't feel that quick when he drove it. (It is a genuine factory model)
I didn't know any better, as I was used to the power it was producing.
I then took it for a diagnostic check on a rolling road, and although no faults were found, it was apparently only pushing out 175bhp at the wheels.
This seemed odd, as this is the bhp for a Cooper S.
I was told Boost levels were good , and everything apart from the power output looked fine.
It was then suggested that maybe sometime in the car's history, the ECU was remapped accidently with a Cooper S map, and I should book it in again to have the ECU's software downloaded to check the validity of the current map.
If it confirmed I had a Cooper S map, they would then remap to a JCW map at a cost of Ł300. I checked this with BMW, and they said that was highly unlikely.
Now, I wasn't present at the Dyno test, and I didn't get a print out of the results either, so I suspected they were pulling a fast one, and I left.
So now at the Specialist garage, they have found that the High Pressure fuel pump isn't working to max output, and this was the reason for the lumpy and poor performance. They replaced the HP fuel pump, only then to discover an air pipe to the turbo had a blockage, and that too needs replacing as the boost level is too low.
I asked why the low boost is now apparent, and not detected earlier, and they said because the fuel pump is now producing the correct pressure, the boost can't cope because of the blockage, and is producing a low boost fault code.
The air pipe is now on order.....
The saga continues...
I'm picking the car up tomorrow, so will report back with the results..