I have a 1993 300e 2.8L gas eng. 104 motor, with 83K miles. It's difficult to start in the cold weather: gas pedal needs to be feathered like its a poorly tuned carbuerated engine. I've replaced OVP relay, engine wiring harness, plugs, injectors, eng. temp sensor, fuel filter. Dealership tested a new throttle body and for $1700 bucks said that the cold start prob. is now fixed.

Can I clean up my old throttle body? Can I spray it down with carb. cleaner to remove any dirt? Can I replaced a small part on it to make it perfom like new? REally need anyones advice!

I suggest trying Mystery Oil in your gas. I use it in every tank.
It seems to really work in terms of keeping my cars engines and emissions systems clean and lubercated.

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Steve Danville
what i did myself.
CPS
rear shocks
MAS x 3.
SparkPlugs (twice)
Fuel pump & Filter
Window switch
replaced both failed horns with Honda horns.
Cleaned ERG Tube
Oil changes
Oil consumption Fix
Brake Pads
A/C Recharge
Anti-Freeze change X 2.
Front Shocks. Monroe. $90
Mercedes Warrenty Work:
Harmonic balancer,power steering clamp. Cat converters.Drive Shaft Bearing.s
Replaced Outer Lower Tie Rods and front lower ball joints at 156,000 miles

Hi Mike, the motor in the actuator may not be able to properly position the throttle blade during cold start-up. I've seen a few actuators cause this problem. Assuming everything else is OK, why not let the dealer install a new actuator and see what happens? They can always re-install the old one if the problem isn't fixed. I've had to use this approach many times. Sometimes the only way to know for sure is to try. Contrary to popular belief, there isn't a conclusive test for every single failure scenario. Good luck.

To ILUVMILS: Dealer did install new throttle body and confirmed that it was the problem. I told them to put the old one in: I figured I may be able to DIY. Hence the call for help.
Can the old one be cleaned or refurbished like an old carb.?

On that car the throttle body harness' go bad, just like the wiring harness. Make sure that the harness does not have any protective material falling off. You have to open the outer sheithing to see the wires. This is a common failure and cant be rebuilt.

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euro 287
Mercedes Technician 7 Years (retired to Hyundai)
2000 Dodge Durango
98 Mazda truck

I was always wondering, can an otherwise good throttle body be salvaged by dipping the wiring in the plastic dip coat used for coating tool handles? The coating would remain flexible for a long time, and assuming the bare copper wires were kept away from each other while curing the part could then be reused. I'd rather try these salvage techniques than spend $1700 simply because of rotted insulation.

I wouldn't try this for the engine wiring harness though, because of the sheer volume of wiring. I'm not that familiar with the throttle body, but I imagine there's a lot less wiring to deal with.

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95 E320 Cabriolet, 159K

Dont blame you dealer! MB (MBUSA) sets the parts pricing & that throttle actuator is the highest priced actuator for any non-ASR application. Suggested retail is $1,380.!! figure tax & 2 hrs labor & WHY are you blaming YOUR dealer for a rip-off???

BLAME MB or MBUSA & leave that DEALER rip-off stuff out of the post!

The same type actuator for most other MB lists for around $900!!!

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I have 3 good reasons why:
1. First they replaced the wiring harness and said the problems fixed.
2. Then in my second visit they said it was the injectors; they replaced and said your problems fixed
3. In my third visit they said the throttle body is the culprit and for sure if it is replaced my problem will be fixed.

Understand that I don't know the difference between MB, MB USA, or a dealer. I am looking at it from a customers standpoint and from the the whole experience. One mis-diagnosis, ok. Two and I'm suspect. Three and I'm floored that couldn't figure it out after having the car for weeks.

Mike, I suggest that you have a long talk with the Service Manager at your dealer. Discuss the details of each recent service visit/receipt and the reason specific work was done. If it seems that they were proceeding on a trial-and-error basis then insist on credit for any/all unnecessary work (parts & labor). Hopefully the dealer or you have the old parts ... I always ask for the old parts, just in case. I'm curious why you accepted the car back after the first service appointment if it was still hard to start. If the problem wasn't corrected why pay the bill? Are you sure that you posted all the relevant details so that the forum members can advise you properly? How far apart and how many miles between visits? Did the Service Advisor discuss what had been done to your car at each visit, and recommend other repair work that youu declined? Our local dealer's Service Advisors communicate the what and why of recommended service items, and whether the items are critical or not. I do the simple items myself.

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Fred Hoelzle

I'd like to offer some insight concerning wiring harness issues/dealer service depts. If I get a ten year old car in with any kind of running complaint the first thing I check is the wiring harness. Contrary to much of what I've read in this Forum, the M104 powered 124 is NOT the only vehicle affected by faulty wiring harnesses. I've seen 140's, 202's, 210's, and 129's with 4, 6, and 8 cylinder engines have the same problems. In my opinion ( and in my shop ) once a faulty harness is discovered the client is informed that the harness needs to be replaced and then the vehicle can be re-evaluated for any other problems. The majority of the time the new harness solves the problem, but it's not uncommon to find something else that needs attention after the harness is replaced. I've seen Mass Air Flow sensors that were damaged by shorted wires. I've seen a few engine control units damaged as well. I've had clients drive their cars with all kinds of minor problems until a bad harness forced them to get the car checked out. Afterward, they sometimes don't understand why the car isn't perfect since they just spent big bucks. I wouldn't waste a tech's time or a clients money trying to troubleshoot a car with a known problem. I think Mike's service advisor made a mistake if he told him the car would be fixed after replacing the harness. As far as replacing injectors for a cold-start problem? That sounds like a guess to me, but like I said in my previous post, sometimes you have to try something and see what happens. Of course if it doesn't work I wouldn't charge the client!

Now back to the question. I've never had any success trying to repair throttle actuators. The electric motor weakens with age and has a hard time overcoming the tension of the return spring. If it was my car, I'd certainly try to fix it before spending that much money. Good luck

EA is the 'electronic accelerator', which is really the throttle actuator--the gizmo that opens and closes to let air into the engine. It is an electronically controlled electric motor coupled to the throttle butterfly shaft. It has a position sensor (variable resistor) for the throttle(accelerator) position, and another variable resistor (position sensor) for the throttle butterfly shaft.

You push on the accelerator--and first a micro switch on the top of the accelerator pedal opens and signals the 'engine control unit' to couple the 'electronic accelerator' motor to the throttle shaft (there is an electromagnetic clutch that disengages at idle or any time the computer says 'tilt'.)

The the EMU/EA checks the position of the throttle position sensor, checks the anti-slip, ESP,ABS systems, and determins if the throttle needs to be opened. If -yes-, then the EA computer sends a series of pulses to the EA motor, which rotates the throttle butterfly open. During this rotation, the EA/EMU checks the actual position of and speed of opening of the throttle butterfly shaft. This continues-always checking first, then opening the butterfly more-until the measured opening agrees with that commanded by the accelerator pedal. The EA/EMU then holds that throttle opening until the accelarator pedal moves (or one of the other systems like engine overspeed, transmission shift computer,transmission torque limiter, ABS,ASR, ESP calls for a reduction in throttle/torque/engine speed.

Fully closed to fully open takes less that 200 milliseconds. Open to closed is faster because the butterfly shaft is spring loaded to close.

The computer system has lots of safety features built in to prevent 'uncommanded throttle opening' that some cars seem to experience. Frankly, I don't see how it would be possible in the MBZ system unless a least 3 systems failed simultaneously--the accelerator pedal switch, the throttle (accelerator) position sensor, and the throttle butterfly shaft position sensor, AND the electromagnetic clutch beteween the throttle motor and the butterfly shaft.

A simple wiring short won't do it because the accelerator position sensor has a known range of values, and changed from (low to high) on pushing down on the pedal. The actual butterfly shaft position sensor has a different range of values, that changes in the opposite direction, so the system would detect the fault as soon as it a hppened and open the electromagnetic clutch.