Low revs throttle surge

[marko96]

Hi everyone I require a little help with a problem on my X5.
I have noticed recently that at low speeds with a very light throttle application there is a surge with the car.
At standstill with the engine ticking over I have applied a little throttle to try and pick the revs up to around 1000 RPM but it surges and falls and continues to do so with the pedal being held steady it goes from tick over to 1400 RPM and back, after 1500 RPM the engine reacts normally to the Throttle.
My thoughts are throttle position sensor or a problem with the Throttle body, I haven't taken any codes yet.

[graemeX5]

Hi

As you say if you can check the codes probably the best place to start.

Otherwise it could be a lot of causes, especially if you have run the tank low recently?

Graeme

[marko96]

These are the codes i got
P0393
P0024
P0128

[Glen]

Hi there if you google the codes you will get the meanings

[henrym3]

2 of them point to CPS B bank and the other to thermostat. Further reading suggests that although it points to the thermostat you should check the temperature sensor reading in the hidden menu, if it's at fault the DME won't open/close the stat at the right time, certainly cheaper to replace than the stat.

[marko96]

Thanks for that I think the temp code is an old one from when the expansion tank was leaking and it lost a little coolant, the CPS codes keep popping up after clearing them, I have tried to find information on the position of the Exhaust CPS on bank B with no luck mine is the N62B44 engine any info would be appreciated.
Also the problem with the Throttle is still there its almost as if there is a dead spot on the throttle pedal where you get nothing and then it goes with a surge it makes town driving very difficult and pulling out of junctions is awkward.

[graemeX5]

Hi

Try this link although it's for an M5 E39 it's basically the same set up V8 as it seems to help explain how to fix it

http://www.m5board.com/vbulletin/e39-m5 ... 5-8-a.html

Graeme

[marko96]

Am I right in saying Bank B is the passenger side bank and cylinders 5 to 8?

[henrym3]

you are correct as long as your looking from the drivers seat or rear of the vehicle

[marko96]

Thanks for your help i will have a go at changing the CPS when I get home I believe its located at the back of the engine on the N62B44 unlike the M62 which are on the front from the info I have gathered it looks like a tight squeeze but I will report back how I get on.
Does anybody have any thoughts on the Throttle action and the dead point in the travel?

[graemeX5]

Hi

Apart from play in the throttle linkages or blocked jets or poss plugs or leads are my ideas, but poss worth getting a diagnostic check done if you have the reader.

It also may be worth giving Jason at BW Chiptine who is well
Know on the forum see the performance section for his contact details and remapped a lot of cars and also resolve the gearbox lurch.

He did my old 4.4 E53 and it went a lot better after it had been to him
Graeme

[henrym3]

I would be tempted, simply because it's virtually free, to clean the throttle body and MAF with some carb cleaner. Also the electrical plugs for both sprayed/cleaned as well. I should imagine all of these problems are caused by the same thing and probably a case of find the, probably one fault and everything else will be fine.

[marko9615]

Just an update on this subject, i have replaced the sensor which was located at the rear of the cylinder head on the N62B44 and cleared all the codes i also replaced the battery and so far i have had no problems with it, so hopefully it is sorted, i still have the dead point in the throttle pedal so a bit more research i think.
thanks to all that have helped. 

[X5-D-Sport]

Here's a possibility....
These cars are "fly-by-wire", as in..., there is no throttle cable. there is a potentiometer / resistor pot at the throttle peddle...

I'm wondering it it is worth disconnecting the connection at the throttle peddle & hooking a multi meter to the pot & seeing if there is a dead spot on the potentiometer... which will be an easy swap out.

You will not need any thing powered up or ignition on to check this.

[marko9615]

Oh well it was too good to be true, more problems, the trans failsafe pops up every now and then the FSU on heater fan packed up and left me with the fan running constantly, the engine is running rough with a distinct misfire at idle and low revs the gear box is clunky when cold and it goes into engine failsafe mode occasionally and the 4x4 inactive/DSC comes on randomly but apart from that it's going great.