Rough Idle
21 Answers
Hello, Sad to say but this is just what happens as cars age. Causes include a need for alignment and tires that may be of various ages use levels (i.e. front vs back). The best ways to fight the rough running is to have regular tune-ups. I have a 1997, and it will run rough at times, but after tune-ups, seems to be a much happier little automobile. =) Best of luck! CarGrrl
The W202 have a rough idle problem. Usually an MAF Sensor.
So at high revs or at high engine load it is running rough? Hand full of problems can cause this... When did you last replace spark plugs and or wires? Thats the most likely culprit. Possibly could be a leaky valve cover gasket which can cause ignition problems. A valves may need to be adjusted or may be sticking Timing problems, ignition or valve timing problems Having not seen the car or being familiar with it, that is my amateur opinion. If it isn't burning oil that is.
MAS air flow meter at it's end, it should be throwing a code about now that says “fuel trim”. Get a new mas air flow sensor insert around $250 at www.germanstar.com you should be good as new. You'd be surprized just how much power you lost with the bad sensor. On the later cars it affects the auto trans shifts too.
Try cleaning the MAF before blowing the 250 on the new sensor. i I had the samething happen to my 95 c280. On the M104 engine things run alittle differently than what is a classic engine for one thing there is no One ignition coil. another is that there is not rotor or distributor. It was one of the first modern engines that we are used to today. Check and verify that each of the coil packs are in good order any with white stuff on the side means its a coil that WILL burn out I lost 2 cylinders after 6 months of that acting up while in a college road trip from NY to FL . I freaked out . The car limped from VA to NY home and I checked the coil it smelled burned and it turns out that it was the original coil from 95 while the other two had been replaced . Check yours and let me know what you see ie. part number and any residues. oh and the throttle plate typically gets dirty from oil so you may definitely want to clean that with some STP throttle body cleaner.
I was having the same problem with my 1994 C220. I removed the MAF sensor and hit it with brake cleaner and let it dry. Installed it and it started perfectly. Simple and cheap. Thanks guys!!
If you use a K&N air filter that can cause your MAF meter to fail prematurely. The most common problem is people will apply too much oil to filter while cleaning. This gums up the sensor. Otherwise they are prone to fail with age.
the part doesnt fail. it just needs to be cleaned.
Depends on the type of MAF.
Same thing happens to my C36 AMG. When I hit the accelerator quickly and firm to merge with traffic sometimes it would start to drive very rough and idle rough until I restart it.
I would recommend using an OBD-II reader and posting the codes on here and we can help you futher.
Don't use brake cleaner, use a MAF cleaner. The brake cleaner has a chemical in it that coats the hot wire in the sensor and eventually cause it to fail the same with carb cleaner. MAF cleaners doesn't not have that ingredient.
It will eventually fail if the hot wire in the sensor gets chemically contaminated, changing the resistance of the wire. No amount of cleaning will fix that. Especially if a brake cleaner or carb cleaner is used on it. A new sensor insert will be required at that point.
Lorne, you are absolutely correct. Now the vehicle won't start. I mistakenly thought brake cleaner left mo residue, but now I'll have to spend the $250 anyway :(
Actually Elizabeth, if you go to www.germanstar.net you can get the sensor insert for less than $250 the price went down, i think it's 125 or 150 now
I use autohausaz.com to get all of my parts. I worked for BMW and a Mercedes dealership and their prices always beat the prices i got at cost and they were the same exact components. I just looked and your MAF is 200. They usually have free delivery too.
i just got over a spell of rough running in my 2002 C200k I fitted a k&n filter in may this year soon after my engine management light came on and it was running rough over the the next 3 months it got worse to the point it couldn't drive it went in the garage to be fixed put a new cat on still weren't right put a new mass on still not right new plugs it still ran rough at idle and flat spots through the rev range em light still on i was running out of things to try started to replace ignition coils done the 1st one no change then it hit me i'd fit a pre oiled k&n filter in the standard air box so with nothing to lose put the paper one back in light went off been running sweet as since that day and better mpg too! after what i went through and it weren't cheap if you have a standard air box on your car your better off with a paper filter!
I have an 1995 c220, when u start the vehicle it runs fine after 5 mins it starts to run rough and I lose power. No engine light
I have an 1996 c220 petrol Pulls No power from coil
1999 C-230 Kompressor: Sure enough, I stopped reading at the point of cleaning with Carb or Brake cleaner and went out, disconnected and shot a few streams of brake cleaner. It ran great for about 3 miles, then the entire throttle range was a flat spot. Scan codes P0301, P0303, P0170, and a few others I don't recall. Limped home and borrowed brothers car for work for a week until new part arrived. RockAuto had a range from $28.99 - $259.98. I looked at mine an it was the Bosch, So I ordered that one at $99.98 for 2-day delivery. Just got through installing and clearing codes. Car runs great!
