vimzin

I had problems with my car feeling randomly slughish out of nowhere. The car would be fine after restart so when I take it to the dealer to get it checked they could never find any problems. Finally yesterday I had the car towed to the shop when it was doing this and they called me up today and said it was the throttle actuator.

What exactly is a Throttle actuator or acculator??

Vadim @ evosport

On C32 throttle plate is controled by a stepper motor - technical term for it is throttle-by-wire. Unlike earlier cars there is no mechanical linkage from gas pedal to throttle plate.There have been problems with actuators.

rguy

I just want to support Vadim's comment with an even more common man's explanation.

An actuator is almost always a motor that acts on some part to move it. Linear actuators are used all the time on shows like Monster Garage to open doors and slide racks on wheels out of the back of a vehicle. You probably know that on a traditional car, when you depress the accelerator that pulls on a cable that is attached to the throttle on the engine. The throttle essentially is telling the engine how to proceed through its available rpm range. A throttle actuator is a motor, in this case a stepper motor like Vadim said, that does the job that the accelerator did in the old cars. It essentially replaces the accelerator pedal as the attachment in the throttle linkage. In current mercedes, your accelerator pedal input tells the engine computer how much throttle you want and then checks it with the throttle nanny to make sure it isn't too big of a request. If it isn't then it tells the stepper motor to start winding in the throttle cable like a big winch which opens the throttle appropriately. The main reason, to my knowledge, that they went through this trouble was to facilitate the introduction of electronic stability programs and anti-slip traction control programs that interact with the throttle to override your pedal input when slippage or loss of control is sensed.

Hope this backs up Vadim and helps more fully explain the process.

By the way, a stepper motor is usually just an electric brush motor that turns a shaft, like an engine turns a drive shaft. The main difference is that the stepper motor uses electromagnetic power and the engine uses fuel combustion power.

Vadim @ evosport

rguy: Very good explanation , could not of done better myself.

vimzin

thanks for the help vadim and rguy.. Just curious thou do you guys think this might have affected my 1/4 mile times?

rguy

Thanks for the props vadim.

rguy

vimzin, your throttle times should be sorely affected by defects in your throttle actuator. The rate at which the throttle actuator opens the throttle, also know as "throttle response", is key to initial acceleration getting off of the line. Also, if your pedal input is not being carried out by the actuator than you are not controlling your car's accleration. This likely means that you are not getting the most out of what you have. I am not saying you are going to take a second off of your quarter mile times, but it is possible. It depends on the severity of your problem. Additionally, it may take no time off of your quarter mile time. Your actuator problem may not have been statistically significant.

vimzin

rguy thanks for your comments.. I just tracked my car and it turned out that it didnt help any with throttle actuator being replaced.. I did a 13.7 1/4 mile time with a trap speed of 102.38.. Im still trying to figure out why my trap speed is a little low any tips on what might be the problem or is my trap speed normal?

rguy

there are lots of published data on trap speeds on the forums, just use the search. Tire traction could be an issue, track surface could be an issue, on a c32 temperature and humidity could be an issue, how many miles are on your rear shocks could be an issue, traction control on/off or dyno mode, rear tire size, tread depth left, auto or manual shifting, driver adaptive transmission mode......the list goes on.

All of these things separately are not that significant, but in aggregate, these can be quite significant. I hope this helps, and I am sorry I cannot diagnose your situation. I would have to take a few rides and just feel the butt-dyno impressions and look at stuff to figure out where improvements could be made.

I didn't think your actuator would give much, if any, improvement, but I hoped it would. Sorry that it didn't. It had the potential to do so, but just wasn't likely.

anasdaouk

hey guys i know its been dead for soo long, but i need advise from you on this issue:
car behaves normally all times until i smash it down full throttle on 2nd 3rd 4th gears it cuts gas totally doesnt accelerate anymore i press the pedal its empty and all i can do is park sbhut down restart and here it gors again...on 1st gear if im not goin sideways seems it doesnt do any problem...nota: car does function perfectly as long as i dont press the pedal fully or do a kickdown i even can go 200km/h without problem...any ideas???????plz help