I was wondering if anyone out there has a 1991 300e with ASR?If you do, could you do me a favor ? Remove the air cleaner housing(3 nuts).Turn ignition switch to ON.Under the hood,rotate crank that is attached to throttle cable to the full throttle position and observe the arm attached to the throttle plate. DOES IT GO ALLTHE WAY TO THE STOP?The stop and arm are under the air inlet of the throttle body. The arm should move toward the left side of the car when linkage is moved to the full throttle position.Iam asking some one to do this because mine is only going 50% of full throttle.Is this how it is supposed to be?Thanks for your help,Dan

Can anyone help me?

I have a 91 300TE. I will try to check this for you.

I'm not sure that you should do this. I've heard that you should not drive the throttle from the engine side of the ASR cars. I hope a real expert can set me straight here.

__________________
Steve

1992 300CE Sportline Sophie
1990 300E Emma - in the family
1979 240D Josephine - sold, but not forgotten
2004 Pacifica AWD

http://web.mac.com/dakota/Mercedes/Home.html

I'm not an expert but have read several posts here that indicate that Dakota is right -- moving the throttle under the hood with ignition switch on will set an error code ...

__________________
Steve
'93 400E

I dont see how if you move the arm that's attached to the accelerator cable? Dan

I believe the engine has what MBZ calls 'electronic accelerator ' (EA) as part of the Anti-slip Reduction (ASR) system.

The EA works by sensing the position of the accelerator with a potientometer {a variable resistor} which is linked to the accelerator linkage. When you push on the accelerator pedal, you move the potientometer which is located in the throttle actuator on the engine. That movement is sensed by the EA computer which then sends an electrical signal back to the throttle actuator to1) engage the magnetic clutch, linking the throttle motor to the throttle butterfly shaft, and, 2) rotate the throttle motor until the throttle plate is opened the correct amount. THE EA computer senses the throttle plate position with another potientometer hard connected to the throttle plat shaft.

All these potientometers, throttle motor, magnetic clutch and inside the throttle actuator housing.

IN ADDITION to the electrical control linkage, there IS mechanical linkage that will open the throttle shaft a small amount to clear flooding.

You should not open the throttle from the engine compartment. That will usually send the system into 'limp mode' which requires a trip to the Dealer or good indy with proper (expensive) diagnostic computer) to clear.

What happens is there is a position switch attached to the top of the accelerator, and if the EA computer senses throttle shaft movement (remember the position sensor) without that accelerator position switch closed, OR the throttle shaft position exceeds what the EA computer is asking for, it figures something is dangerously wrong, the engine is trying to run faster that the accelerator is asking for, and immediately disconnects the magnetic clutch and sets the 'limp in' mode.

This system prevents 'unintended acceleration' from happening.

The variable resistors on the accelerator linkage changes from high resistance to low resistance as you push on the accelerator, while the throttle shaft position sensor goes the other way and the computer continuously monitors the positions so that if one changes instantly (like a loose connection ), the system again shuts off.

Sorry, Dan, I guess I won't be testing my car to see how it behaves. However, I do rev the engine from under the hood when I set the duty cycle, i.e. to rev the engine to 2000-2500 rpm to compare the reading to that obtained at idle. So far no problems (knock on wood).

Kebowers, thanks so much for the info on the ASR system. I looked today at the wiring diagram and at my accelerator pedal and found no switch. I think my system,1991(early ASR system, m103 engine,CIS injection)differs slightly component wise from the newer systems.My system consists of the accelerator cable that is mechanically connected to the throttle potentiometer (R-25).The throttle pot is electrically wired to the electronic accelerator control unit. The control unit processes the signal and outputs it to the throttle actuator(m16/1) This throttle actuator lives under the intake and is connected to the throttle plate by an 8 inch adjustable rod.There is a safety switch in the throttle pot that is open@idle and closes@4-6 degrees open throttle.There's also a safety switch in the throttle actuator that is closed @ idle and opens 8-12 degrees output shaft rotation in the open throttle direction.If the accelerator pedal is in the idle position but the throttle actuator remained in the open throttle position these switches would DISAGREE and open the circuit to the fuul pump relay and shut the engine down.I really don't believe moving the throttle linkage at the THROTTLE POTIOMETER, where the cable attaches can do any harm since you are only eliminating the use of the accelerator pedal and cable and this systems safety features are in the throttle pot and the throttle actuator .Thankyou so much for your reply.Dan

Hookedon210s,thanks for your reply,I definitly dont want you to do any damage to your system.If you have a 91 with a103 engine and move the linkage where the throttle cable attaches , I dont think you can do any harm.See my post above. I still dont blame you for not wanting to do this if there's any doubt. Thanks for your replies,Dan

Dan, my system is like yours-cable driven from the accelerator pedal to the pot under the hood. I just tested it and my throttle actuator rod goes all the way to the stop in a delayed, notchy fashion. In response to a "floored" pot it initially responds immediately to open approx. 50% and then continues to open in notches to full throttle over a period of 2 to 3 seconds. It will only do this 1 or 2 more times before the key must be recycled to get the same response. Hope this helps.

Thanks for checking it out for me.I really appreciate it. Mine goes to about 50% and then vibrates but refuses to advance past 50% of full throttle. I guess it's trying to behave like yours but there must be some small problem that is causing it to stop short. I guess I'll have to investigate further.Thanks so much for checking it out for me,at least I now know what proper operation should be. THANKS,Dan