Hi,

Lately the idle speed on my son's 1988 190E has been very erratic. It usually runs around 800 but for no reason sometimes goes as high as 2500 and gets stuck there. If the gas pedal is hit a couple of times it usually goes down to normal. Occasionally when hitting the gas pedal does not work he has to shut the car off and start it again. It happened with both a warm and cold engine.

I tried cleaning the linkage and lubricating but it still happened. Any suggestions would be greatly appreciated!



Thanks,

Bob Koziak
1988 190E 128K
1983 300D 116K
1990 300E 87K

 

I had the same problem with my 79 450SLC. I cured mine by taken off the air cleaner and tightening the acclerator linkage and using hydraulic oil to lubricate all the "joints" right up to where the acclerator comes out of the firewall. Then I took some WD 40 ( not recommended by MB but neater for inside the car the hydraulic oil which is the recommeded lubricant for the linkage) and sprayed the linkage from the pedal again at the joints. I pressed the pedal several times and felt it loosen up then I went back under the hood and moved all the joints to make sure they were free, especially around the throttle body. When I turned the car on, it was a cold day, it ran at 1200 RPM and gradually dropped down to 800 RPM which is within tolerance according to the shop manual. I did adjust the idle screw and CO2 screw a hair as it was running slightly rough. For a couple of days it would jump back up to 1200RPM at times when I stopped, but since then it is going back to idle without a problem. A couple of weeks later I cleaned the TB with TB cleaner, don't use carb cleaner if the car has a TB. being careful of the sensor. Also check the vacuum lines for the distrubutor that come onf the TB, at least on my car there are two. On later cars, this might be a function of the computer. I replaced one, and now the car runs as smooth as slick. One other point, if your sons car has cruise. you might want to take look at the cruise cable and where the end of the cable touches the accelerator, mine was out of adjustment, the ball at the end should just touch the accelerator with very little to no free play. Again your sons car is newer so this also might be computer controlled. Worst case if the above doesn't work there is a idle control module on the V8 in my car it is in front of the TB and it cost Big $$ to replace even fo ra DIY'r. I inagine there is one of these on your sons car also.

Go to your dealer's parts deparment, and asked them if they can copy the schematic for the accelerator and it conponents. I find the two dealers in this area are usually very cooperative with this kind of thing. Especially if you buy something, like a oil filer, air filter etc.

what I did to "fix," t was a neglected accelerator linkage. I was lucky. I bought the 450SLC last October as a project, it was rust free, good interior everyhting (parts wise) was there. The previous owner had the engine and transmission rebuilt in 95 and clocked only 5K miles since. He changed the fluids faithfully, but didn't maintain things like the linkage, brakes, etc. So far I have spent around 2K on basically maintaince and replacing vacuum lines and door rubber, two calipers. and a few other items. The car had 114K went I bought it and the day my son and I picked it up I drove it 125 miles home with incident, except it burned almost the enite tank of gas, (around 20 gallons) since then with the linkage fixed the TB cleaned new plugs and EXP2 fuel system cleaner the highway mileage has risen to 18mpg and around town 13mpg, this is from around 8mpg to 11 mpg before. Good luck and let us know if my suggestions helped or can be done on your sons ride?

 

I had the same problem on my S320 and my daughter's c180. I fixed the problem on both cars by spraying Carburetta cleaner on the air intake butterfly valve. This cleans the valve and allows it to operate freely. An easy fix.

 

pcroft: Yep it worked for me also. One thing I have to repeat, is the cruise control, if equipped, the "setting" for the cable that leads to the actuator has to be in perfect adjustment against the throttle. Having a shop manual helps, but it is vague at best as these manuals are written for techs that have been trained and are more references. But what I found if the ball on the cable is too close or pushing the on the accelerator rod your idle will be high also and the cruise doesn't work correct. there is an adjustment nut. It is a two nut set up, one to loosen the long adjustment nut, The ball has to be set as to not have any freeplay against the throttle, whick is ambigious a best, but after a couple of tries I got it just barely touching the accelerator portion it rest on. That seemed to be the final "fix" for the high idle. Everything you did and I did help and did bring the idle down to almost acceptable levels in drive. however in neutral the idle when up again. Not as high as before, only to 1K rpm. the adjustment of the cable for the cruise finally "fixed" the problem. So Bobby K if the idle is still a bit high and the car has cruise adjust the cruise cable and while your at it make sure there is nothing that is hindering its motion t othe acutator. The spark plug wire were laying on top of my cable I disconnected the cable form the adjustment and routed over the top. These freed it up. My cruise still doesn't work correctly, it wil accelerate but not hold, I did all the trouble shooting and found the cruise switch on the coluum is worn internally I presume, I have a new one coming, easy fix on a 450SLC for 79 the turn signal and cruise can be removed without taking anything apart and replace easlily.

pcroft, One thing I would highly recommend and so does the factory. Lubicrate the linkage with hydraulic oil, especially at the joints, right to the where it goes into the firewall. I cleaned my also, but on my 450 there are quite a few "junctions" with ball ends, in these multi link accelerator and after a while they wil start to stick and wear without lube. Also, the ball ends have a tendency to fall off so make sure they are tigh. The factory recommends lubricating at B service or anytime the engine is cleaned. In all my years of DIY on cars I honestly have to say, I have never seen such a complicated arrangement for a throttle/ accelerator linkage in any car I have owned whether carb or FI. But it is Mercedes and made by Germans ( I am german) and they do have their way of doing things.

These early or mid production SL were cars that Mercedes made changes to most every year. As far as I know when the 190SL with the 4 cylinder it had Mechanical FI which for all intent and purpose was not a new comcept, but one that was difficult to control back then and not too many commercial cars came with them. I looked at a 75 SL and it had the same muti linked accelator, and the owner said it is a pain in the ****.

I read a book on SL's excellent material. One thing I picked up was brakes. Mercedes started using disc brakes in front onthe 190SL as I remember and drums in the back. The time period was the 50's Except for the Corvette, American cars were decades away from disc brakes and even today, there are plenty of American cars that have them in the front only/ Mercedes decided in the second generation of street SK to equipment them with 4 whell disc as a standard. Decades ahead of American manufactuer's. Ditto with seat belts. Also, Mercedes on their own crash tested cars as early as the 60's to improve passenger safety. The government had to force American cars manufatuers to make cars safer. The only reason we won WWII INHO, was the Allies had a better supply chain and logistics then the axis nations. We basically moved our troops and supplies faster to the fronts.

 

Would you have a diagram for the 190 2.3 drive belt????????????????

 

Yes the 190sl had front discs. The 50's 300sl had all 4. 65 230sl's and all sls since have them on all 4. Love these benz's. Gotta admit I could get 365 HP from a 327 Fuely vet in what? 63? It took MB a long time to mass produce 365HP. Right?