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Car Forum / BMW Cars / June 2006Strange Acceleration / Performance behaviour - E46 '99 318 Saloon
It would be great if someone could advise the potential cause of the below behavior. The engine when still cold gives a nice acceleration feeling when changing from 1st to 2nd gear at 1500rpm. The MPG indicator stays above 20. When the engine at normal temperature (temp needle in the middle) and performing same gear change on same revs the acceleration is poor with the MPG indicator going below 16. I had a BMW specialist test driving it but he couldn't feel any performance issue. I know I have the "sticky accelerator" problem which has been fixed only through "cleaning" by the BMW dealer. Any advise is mostly appreciated. BR / M > The engine when still cold gives a nice acceleration feeling when > changing from 1st to 2nd gear at 1500rpm. The MPG indicator stays above 20. > > When the engine at normal temperature (temp needle in the middle) and > performing same gear change on same revs the acceleration is poor with > the MPG indicator going below 16. Maybe the temperature sensor for the computer DME is bad or has dodgy wiring. The engine could be in cold start mode all the time.  SignatureWho needs a life when you've got Unix? :-) Email: john@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage! Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html www.Strathspey.co.uk - Quality Binoculars at a Sensible price Auuto? Sounds like an effect of whether the gearbox oil is cold or hot. > It would be great if someone could advise the potential cause of the > below behavior. [quoted text clipped - 16 lines] > > BR / M > Auuto? > [quoted text clipped - 20 lines] >> >> BR / M many thanks for the info.. it is a manual... It is true that the clutch is smoother when the engine is cold. After a couple of miles the clutch hasn't the same smooth feeling. But how could the gearbox oil be related with the above behavior ? BR / M > It would be great if someone could advise the potential cause of the > below behavior. [quoted text clipped - 15 lines] > > BR / M I'd say you are shifting way too soon. BMW engines are made to rev much higher even under normal conditions... Signature-Fred W >> It would be great if someone could advise the potential cause of the >> below behavior. [quoted text clipped - 19 lines] > I'd say you are shifting way too soon. BMW engines are made to rev much > higher even under normal conditions... I see your point... it is also the case the performance feels poor when the engine is at normal temp and I shift gears at higher revs - the MPG indicator also shows higher consumption. What else could it be assuming same behavior on gear shifting at higher revs ? BR / M >>> It would be great if someone could advise the potential cause of the >>> below behavior. [quoted text clipped - 26 lines] > What else could it be assuming same behavior on gear shifting at higher > revs ? Sounds to me like you are running rich. I'd get someone to run diagnostics on it. >>> It would be great if someone could advise the potential cause of the >>> below behavior. [quoted text clipped - 28 lines] > > BR / M Well, it could be that your O2 sensor is going bad. In the first few minutes of cold operation the ECU is running "open loop" (meaning without the O2 sensor feedback) until the sensor is deemed to be fully up to operating temperature. Once it does go "closed loop" if the feedback signal from the sensor is wrong for any reason the engine will run rich or lean. Eventually the signal will exceed hard limits coded into the ECU and it will throw a "check engine" code. A quick exhaust gas analysis at a competent shop should tell if that is what is going on... Signature-Fred W >>>> It would be great if someone could advise the potential cause of the >>>> below behavior. [quoted text clipped - 39 lines] > A quick exhaust gas analysis at a competent shop should tell if that is > what is going on... Ding ding ding, we have a winner.... maybe... But the engine should really be running like crap if the O2 sensor is bad... But this car probably has 2 or 4 O2 sensors like my 96 M3, and so I would think some codes would be getting set. I guess 318, probably 2 sensors. Thanks, Mark >It would be great if someone could advise the potential cause of the >below behavior. [quoted text clipped - 15 lines] > >BR / M 1500 rpm on a 318 is killing it. You need to rev it more. I think you do more damage by revving it that low than revving it higher up. > >Any advise is mostly appreciated. > > > >BR / M > > 1500 rpm on a 318 is killing it. You need to rev it more. I think you > do more damage by revving it that low than revving it higher up. ..but why should it work when cold and not when hot? It's small problems like this and very poor customer service that can make owning a newish BMW a very bad experience. Usually it's a case of "computer says no" when you think there might be a problem. >> >Any advise is mostly appreciated. >> > [quoted text clipped - 4 lines] > >..but why should it work when cold and not when hot? Well, the engine management system changes the amount of fuel needed when the engine warms up. My guess is that this changes the characteristics of the engine a bit. I would make sure all sensors are clean (in the intake) and make sure there are no stored codes. >It's small problems like this and very poor customer service that can >make owning a newish BMW a very bad experience. Usually it's a case of >"computer says no" when you think there might be a problem. Read the codes. |
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