Greetings! I have searched the forum for similar problems, but haven't found anything definitive for my problem (fuel cap, fuel filter, MAF sensor, distibutor/wires, etc. were all common suggestions). My SL500 has been running fine, and have had no stalling or rough idle symptoms like most others posted. No CEL light either. However, when exiting the freeway on my way home yesterday, all of a sudden I noticed a miss in the engine, and it began to run really rough, obviously not running properly on all cylinders. As I limped the last mile or so home, it got progressively worse, almost to the point where I could barely go anywhere. There was no smoke, no fluid loss or any other obvious signs of any problems. I thought maybe I got some bad gas, since I had just put fuel in a few miles before getting onto the freeway, but it ran fine for about 5 miles.

I have checked the oil (seems good, nothing abnormal), removed the air filters & cleaned the MAF sensor with CRC MAF Sensor cleaner (coincidentally used this on my other German vehicle recently), and pulled a couple of plugs as well (again, seemed normal). Any suggestions what can be causing this problem? I let it sit overnight, and it started right up initially, but just runs very rough, and it is not "driveable" in my opinion. It is very, very sluggish from a stop, and will get up to speed eventually, but never run smoothly or with any power. I have driven around the neighborhood a bit, and the problem seems constant. I called my local (45 miles away) MBZ dealer, and the service advisor I spoke with said I should change cap/rotor.....make sense? Any help would be appreciated since I don't think I can drive to the dealer safely, and would prefer not to tow it if possible. Thanks in advance.

 

how many miles are on the car? have you heard any funny noises when you first start your car. like what might be the chain slapping against it's cover. hopefully your timing chain didn't skip a tooth or two.

 

could be a voltage problem with battery or alternator. bad gas maybe too. crank position sensor maybe going bad.

 

Mass Air Sensor. Had the same problem with my 2001 SL500. Part is about $260. I paid $400+ at dealer for diagnostics, part and installl. Power back, shifts correctly and runs smooth. Doesn't mean that this is your problem, but it fixed mine. Hope this helps.

 

I've got the same thing going on with a 93. It's my mothers car she stores in the winter. Battery has been dead and it was two quarts low, charged it and got it running. It was running rough like tst31 described right away. Yesterday i went up to take a look at it and it started up and idled nicely and revved smooth so i took it for a 5 mile trip, ran great! until i got back to her road it started running like it was in limp mode all of a sudden. no lights or anything in the dash just feels like it's not getting fuel or something. I'll clean the MAF, otherwise open to suggestions. Thanks

 

Thanks for all the replies! Turns out my problem was inside one of the distributor caps. Apparently, the rotor bracket failed in a major way, which of course made me lose all 4 cylinders from that cap. So, now I need a new distributor, rotor, bracket, cover/seal.....etc. I was really surprised because the vehicle has been running really well. It liked like the bolt that holds the rotor bracket got loose, which led to the failure & cap/beaker puree :-)

 

I failed to add earlier that my car has 109,000 miles. There have been no noticeable noises upon startup or any other indicators that an issue may occur. I am a garage mechanic & do most of my own basic services, so I am pretty in touch with my vehicle when it comes to irregulaties.

 

Any idea how I can get the remaining part of this dowel that remains? It is the dowel that helps align the rotor bracket and I believe it is pressed inside the gear or whatever is behind the seal. You can see it just about between 5 and 6 o'clock area. I have to get a new distributor, rotor, bracket, seal, and replace that dowel...any ideas outside of OEM? I know NAPA has the cap/rotor, and a the bracket, but should I stick with OEM? Thanks in advance.

 

use oem parts. I've had great luck with Auto Parts at AutohausAZ - OEM Auto Parts - Discount Replacement Parts, Resources and Car Care Tips for oem parts. generally a lot less in cost than a mercedes dealer for your car's most used parts.

 

looking at your sheared off pin, what a mess. that rotor adaptor aligning pin looks like it's pressed into the cam alright. i couldn't find anything in my service manual for that problem. I don't think an easy out will do the trick, other than break off in the pin. you had better check with a good servicer on this one. I don't know if you will have to pull the cam to fix or not. you might think about changing your timing chain while you're in there. mine started slapping at 110k when starting, more of a quick zipping noise. it could last another 50k or more, they are tough, they won't likely break, but could jump because they stretch. My servicer was able to used the old chain to thread the new one to save time, clever of him. knowing I had replaced the guides a few years earlier he didn't have to do a front of the engine teardown. however you may want replace the chain guides too, which will require more labor and money of course. but you'll be good to go for at least another 110k. the front crank seal might be a good idea too. maybe chassis221 could give us some input, especially on the pin.