I Give Up!

[944s2c]

I have a 91 300e with asr.The output of the throttle actuator slowly decreases over time until the car goes into limp mode.I've replaced the throttle pot(R-25) and the throttle actuator with no results.Can the brake switch,wheel speed sensors,coolant temp sensor , park sensor possibly be causing this. I'd be very happy to PAY some one who is an expert on these early e-gas systems for their time to help me trouble shoot this problem.
Any help or recommendations would be greatly appreciated!
Dan

[944s2c]

Anyone???

[Gilly]

91 300E, isn't that a 103 engine with CIS-E, or possibly a M104 with CIS-E??? Pretty sure it's a 103 engine, only the coupes and SL's had the M104 at that point, and even that was CIS-E. Shouldn't have E Gas.

Gilly

[944s2c]

Hello Gilly,thanks for your reply.Yes it is the 103 engine. 1991 was the first year that mercedes offered ASR.These early systems had the accellerator pedal mechanically linked to a throttle potentiometer(R25) in the engine compartment . Throttle potentiometer is electrically tied into the ASR/ABS CONTROL UNIT(N30/1) and electronic accelerator control unit(n4/1) These are wired to the electronic accelerator actuator(m16/1).There is a 10"pushrod from this unit to the throttle arm on the throttlbody.The problem is that the the throttle actuator is only moving through about 50% of its possible travel which is limiting engine output.I observe this on the throttle actuator and by reference to the W.O.T. stop on the throttle body...it only goes about 50% of W.O.T. Any ideas as to what can limit the movement of the throttle actuator? Wheel speed sensors?throttle position sensor?brake switch???? I know a little bit about this system but could really use some help so I don't waste money and time on unecessary repairs.THANKS....Dan

[Gilly]

It's be nice if someone with more ASR experience on an earlier one like this would chime in, so let's hope for that.
The actuator you refer to is I believe actually the cruice control actuator, but if this early one is really "full range" like you state, then it uses the cruise actuator for manually retarding the throttle.
I would suspect that it uses one of the front wheel speed sensors and 1 or 2 of the rear to compare for slip detection. Possibly one of the sensors is going bad. Are you getting an ASR warning light, or the orange triange light coming on when it does this? Can you describe when or how often it acts like this?
If you're getting a warning light, has anyone checked for a code, or doesn't this store codes? If it doesn't store codes you're in for alot of testing, most easily done with a "break out" box, and A to Z doesn't rent those!
Does the cruise control work OK? Have you tried removing the link to the actuator? I assume it would at least make the car operate normally, but with no cruise control (I love cruise, I'd fix the system if only to have an operable cruise control!)

Gilly

[Kebowers]

You REALLY do need to properly diagnose these system or you can throw $1000's at it and not fix it. Anything from bad tail light bulb/contact to faulty (low voltage) alternator can cause 'tilt/limp'

Bad wiring harnesses are probable if they have not been replaced, but PLEASE either go to the Dealer or a good Independent for proper diagnosis. There really is no other way unless you want to buy the diagnostic equipment yourself (>$1500 to start)

[944s2c]

Gilly,I don't get an ASR light. I don't think this system stores codes.The cruise works.The orange triangle light only comes on when wheel slip is detected,which is normal.It always has 50% or less throttle movement...even when I turn key to on and move throttle linkage under the hood with the car parked.The system operates normally EXCEPT this reduced throttle movement .The longer period of time I drive the car the less throttle movement I get.Yes I have disconnected the rod from the actuator and attached it to the mechanical linkage which allows normal operation of the car except for cruise and the throttle retard feature of ASR. How can I check the wheel sensors.I wonder if I can swap the ones from my 91 300 sl????

[944s2c]

Kebowers , thanks for your reply.I am very close to seeking out professional help on this. I just don't want to get into a situation where they throw parts at it until it goes away...I can do that.If I could find a good Tech here in pittsburgh, I'd be happy to let them look at it if they were going to honestly diagnose the problem.I am an aircraft tech by trade and have been able to do all my own work for the past 20 years...but this has me stumped!Thanks for your reply, Dan

[Gilly]

Sorry I deleted my last post, I had read your last post incorrectly.

If you get normal throttle range with the actuator disconnected, I would think that there is some problem with the actuator itself, possibly in the way it's mounted. I assume you had the "identical" problem previous to replacing the actuator, right? Has the car ever worked correctly since you've owned it? What is the history of the problem and your history of ownership, can you go into that a little bit, a little background info?
Have you checked into how much range of movement the bellcrank on the actuator has in comparisom to how much range you need to move the throttle to wide open? Maybe, just as a suggestion, I know you don't want to run off and buy anything else yet, maybe someone sold you an actuator for a non-ASR car? Maybe you can ask Phil what the correct part number is for this car.
Also I believe the actuator, on a simple "cruise only" car, you can get the actuator to mount 4 different ways (4 bolts in a square configuration), so maybe it got mounted to the bracket 90 or 180 degrees off? Just another idea.

Gilly

[944s2c]

Gilly, I have owned thie car for 7 years now. I began to notice the car was sluggish about 16 months ago. I drove from pitts burgh to Erie last summer and when I got to Erie, I noticed I had to push the pedal to the floor just to get the car to pull away from a stop light.I didnt have an asr light on.I turned the key off and back on and had better throttle response for a while,but within 20 minutes the problem was back. When I ordered
the throttle poteniometer,and the throttle actuator I used my VIN and the part numbers on the parts..I am positive I have the right parts!The rod that goes from the throttle plate to the actuator is adjustable and required no adjustment after installing the throttle actuator so I am sure I have it properly mounted. The throttle actuator has a possible range of motion of about 90 degrees stop to stop.The problem is that for some reason, mine is only initially rotating about 45 degrees initially and then ,the longer it is driven,the output decays to almost zero.Something is ruducing this out put. Any ideas??Thanks for your reply,Dan

[Gilly]

Nope, I sure don't. That's a CIS-E car, and if you push the pedal to the floor, the throttle should be wide open, it's not like an E Gas (EA) car where it's an electronic throttle motor. Foot to floor=wide open throttle. Unless there is something extremely funky to that linkage that I'm not aware of that allows the ASR/Cruise actuator to "over-rule" the throttle input. I would consider trying to disconnect the electrical plug-in for the actuator next and drive it like that. If it still behaves the same way, I'd think along the lines that there is a linkage problem somewhere. First I'd try to determine what it is about the linkage that allows the actuator to have precidence over the throttle.
I can try digging around in my info here at home for more ideas.

Gilly

[944s2c]

Gilly,did some more trouble shooting today.With the key off I reached down and grabbed the link onthe throttle actuator and rotated in the WOT direction.It pushed the throttle plate to the stop. I disconnected the link that runs between the actuator and the throttle plate and connected it to the mechanical linkage and the throttle plate there by leaving the actuator mechanically disconnected but electrically connected . Unpluging it would not allow the car to run without pushing on the gas pedal because there is a safety switch in both the throttle pot and the actuator.The linkage from the gas pedal to the throttle plate is puruly mechanical at this point and I am able to achieve WOT.The cruise doesnt work nor does the throttle retard portion of ASR. The braking function of ASR still works whenever wheel speed is detected.I sure need to find out what is causing my reduced actuator output.THANKS FOR YOUR HELP, Dan

P.S. Know of a good Benz mechanic in the Pittsburgh area??

[944s2c]

Sorry I had trouble getting that last message to post and when it did it posted 3 times ...sorry!

[Gilly]

You can click "edit" on the unwanted posts, then check the box next to "Delete this post?", then the unwanted post/posts will be deleted.

Gilly

PS No, I don't think I know of any MB techs in PA at all, much less a good one.

[Pete Geither]

I know of a good Benz mechanic,,,, he's working on one of mine right now. E-mail me and I'll give you his number.