My BMW 323C slow down quickly when my foot off the pedal
I have a 1999 BMW 323 convertible and it decelerate quickly once I let my foot off the pedal even at neutral gear. I worry that the mechanics did not fill enough oil or over filled oil when he replaced the auto-transmission oil recently. He used 3 bottles of 1-quart oil. I do not hear any strange noise, but the engine's warm up in the morning makes a big noise.
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Re: My BMW 323C slow down quickly when my foot off the...
Thats interesting considering these BMW auto boxes have about 10 quarts of oil in them, when chainging the trans oil not all of it comes out but it should be at least 5/6 quarts. You need to get the oil level checked asap.
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Now iam not sure about this and no doubt iam totally wrong but as this is a later model and a american market version then it could be the fly by wire throttle control their is no cable but a variable voltage control inside the car and a electric motor on the inlet manifold and if this is the case i would suspect the pedal unit inside the vehicle ? but again no doubt i will get a verbal slap as being wrong .
It's not a malfunction- this particular auto's idle rpm speed is low and it simply lacks the power to hold on the gradient of the slope- until of course you step on the accelerator pedal.
There is a very brief lag time from the moment your foot comes off the brake pedal to the time it reaches the accelerator pedal; such that by the time the torque converter is able to "perceive and respond' to your brake pedal to accelerator pedal movements, the car will- by the vary nature of gravitational force move in the direction it is being pulled until a force of equal or greater resistance is applied to either hold it in position or move it in the opposite direction.
By its very definition, a torque converter is a type of fluid coupling that is used to transfer rotating power (the engine) to a rotating driven load (the drive train)- that is the transmission, drive shaft, axle gears, and wheels that the tires are mounted on. [The transverse engine set-up is different than an in-line engine design, but the operating principles are basically the same]..
Automatic transmissions work on the same principle of a water wheel. As the current force of the water drops into the vanes of the wheel, it is converting that water force or pressure into useful forms of power as the wheel spins.
If the current flow of the water is so slow that the paddles of the water wheel are unable to detect any force, the wheel does not move- therefore no power-torque output.
Likewise, if the engine is idling too slow for the vanes in the torque converter to detect any push the transmission into power-torque output, then the car is going to freely go into the gravitational direction of the slope.
Could be several things, a vac leak, dirty throttle body, or faulty idle air control valve. The computer controls idle speed by how much air enters the throttle body thru the valve. Usually a vac leak would speed up the engine unless it is causing the rough idle.
after checking fluid level is correct, try this, to see if it improves...
into drive,let car accelerate without any gas(do not touch pedal)to max speed (about 30/35mph).stop,then with 1/3rd gas pedal,accelerate to max speed(do not move foot)stop,then foot hard to floor,upto about 60mph,then stop.then only using a max of 1/3rd gas pedal,drive for about 15miles.you have just reset the drivetrain computer setings....the car is fitted with a computer controlled fuzzy logic gearbox,it will try to make you drive as eco as poss,but if used harshly the gearchange can be harsh up and down.....
if driven gently 4th will engage at 43 mph,with a slight clunk.
Ok Slow deceleration rev responce was part of the ECU software to keep the emissions down ,however if this has only just started you can try to reset the IAC valve ,the procedure is as follows.
Turn ignition key on ,unplug the IAC valve ,turn the key off ,replug the IAC valve. do this 3-4 times .Then start the engine while holding the gas pedal to 2000 rpm ,then slowley let the go of the gas pedal till the engine idles .
The IAC valve is located on the throtle body and has 4 wires to it.
Sometimes the throtle body needs to be cleaned and then reset.