Need some help. I have a 2002 C240 and have never had a problem with it. Only has about 55K miles. Just today, it started to idle weird when I would stop. I feel a minor vibration all over the car however, the rpm's are not changing at all. When I go to take off everything is fine. If I put it in reverse and just let it cruise backwards the "shaking" is the worse. Any help? I also put 89 in it a few times and I was always running 93 for gas. I was on 3/4 of a tank and filled it with 93, haven't seen much difference at all. Thanks!
The first thing I would do is connect an OBD2 scanner on it, check for pending codes (codes that haven't get illuminated the check engine light) and check that the other sensors have reasonable readings (ie. the VSS should be zero when not moving, the TPS should be 0 when not pressing the gas pedal, RPM, fuel trim, load, etc. I know an ODB2 scanner is an investment but these days you can't just tweak carb settings and twist distributors until it sounds right, everything is done through sensors and computers (I just fixed my kid's SLK's turn signals, a $790 computer controls the turn signals, no $10 relay, it's not yesterday's hotrod). Somethings you can do as just maintenance, in case you haven't done so already is clean in the MAF sensor with MAF sensor cleaner, clean the fuel injectors with the system that attaches to the fuel rail (not the pint of additive you put in your gas tank), clean or replace the air filter, clean/regap or replace sparkplugs (I know they say they last 100K miles, but reality is different).
Need some help. I have a 2002 C240 and have never had a problem with it. Only has about 55K miles. Just today, it started to idle weird when I would stop. I feel a minor vibration all over the car however, the rpm's are not changing at all. When I go to take off everything is fine. If I put it in reverse and just let it cruise backwards the "shaking" is the worse. Any help? I also put 89 in it a few times and I was always running 93 for gas. I was on 3/4 of a tank and filled it with 93, haven't seen much difference at all. Thanks!
I was experiencing something similar with my 01 240. only in drive at a low speed or stopped correct? If in neutral it stops?
For me it was the beginning of my right motor mount going. At first it did it occassionally and gradually it did it more often and then I was hit by someone in the front left side of my car and that is what did it in and it was constant after that until I got it fixed obv. Find a shop to diag it, not the dealer. it was about $450 job @ $80/hour. This was through an independent shop. I believe the part was about $175 from mercedes.
Ok well here is the kicker. It seemed to have no vibration this morning and after a couple hours of driving it came back slightly. Only problem is that it still happens just as bad when it is in neutral. Go figure huh? My first impressions of the problem was maybe bad gas. I am not sure what the deal is at this point. Weird that it would do it in neutral also. Have you seen that before?
Ok well here is the kicker. It seemed to have no vibration this morning and after a couple hours of driving it came back slightly. Only problem is that it still happens just as bad when it is in neutral. Go figure huh? My first impressions of the problem was maybe bad gas. I am not sure what the deal is at this point. Weird that it would do it in neutral also. Have you seen that before?
I highly doubt its the gasoline. I dont see how gasoline would do that. I havent seen the same scenario happening in neutral. But considering i ahve been an mb owner for less than a year i suppose its likely that i havent been exposed to that. if you dont know what it is and no one on here can specifically put their finger on it i would suggest gettin it diagnosed and go from there.
I have found this website 100% helpful but in the event you arent getting the responses that best answer your question or issue, try another source.
Thanks for everyones advice. I will have it diagnosed and see what they say. I just wanted to make sure that it wasn't something stupid that I wasn't thinking about.
Thanks FrankW! I had a friend look at it this weekend and they were saying there was some kind of misfire somewhere. I will ask the independant service shop here check that out. Seems like a motor mount is a problem with all of these "C" classes. Thanks again!
Your having the problems too? I really wasn't worrying about it too much seeing that it doesn't affect the ride at all and the drive is the same. Has it been consistant over the last year or do you have good days and bad days with it? Someone mentioned to me that maybe something isn't firing correctly. ??? I guess it is time to trade it in then!!! ;o)
Did all that you suggested, MAF, fuel injectoers and plugs. But started running rough again - to the point I could not drive it. Took it elsewhere, they found a cracked plug so replaced them (again), and ran great for 15 minutes then the same problem. Their latest diagnosis relates to the accelerator that is apparently "fly by wire" and the sensor is sending the wrong message. Can't just replace the sensor so $200 later for a new accelerator pedal assembly hopefully we are on the right track...
Idling rough - after replacing catalytic converters
The outcome was - it was not the accelerator pedal, or the fuel filter - finally ended up at the dealership where they pulled off the cats, and when it ran fine, replaced them ($1,800 including air flow meter) and has been running fine ever since. Well, almost, it idles at 6,500 but has a bit of a vibration. It is not the motor mount, already had that checked, it is not the plugs, already had them replaced with the last service. Any other ideas? Thanks.
i had a similar problem on my 03 c230, and had it fixed at mercedes still under warrenty but I had a hole/leak in my intake, well thats atleast what they told me.
That is interesting, surely that is something they should have picked up with the cats replacement? Here is a further piece to the puzzle. When I start up to drive it does not acclereate properly for about a mile, feels like it is not firing on all cylinders, then finally starts to run smoothly. Did yours do that?
The outcome was - it was not the accelerator pedal, or the fuel filter - finally ended up at the dealership where they pulled off the cats, and when it ran fine, replaced them ($1,800 including air flow meter) and has been running fine ever since. Well, almost, it idles at 6,500 but has a bit of a vibration. It is not the motor mount, already had that checked, it is not the plugs, already had them replaced with the last service. Any other ideas? Thanks.
I had my leftside cat replaced with an aftermarket unit ($250 installed) on my 2003 C240 The stealership quoted me $1250 for each side, here in Canada.
You were experiencing a clogged exhaust path (backflow) that probably carboned up the exhaust valves and/or seats. There is a service bulletin to clear this by changing the plugs and running the engine at 4000 rpm for 10 minutes if they are lightly carboned. You would need a boroscope to see for sure.
sounds like a missfire but if people who wants to know if its there motor mount ,have some one stand next to ure car (not in front lol) n the one in driver seat press the bake n gas at the same time. and ask the person out side to c how much the motor is lifting. it shoul drock botu an inch or two any more u need motor mounts
i have a 2003 c240 and it does the same exact thing once in a while. I am planning on swapping spark plugs this weekend to see if this fixes the problem. My co-worker has a 2002 c240 as well and he is also going through the same thing.....he was advised by the mechanic that he needed some updates on the ECU. But i am not sure if this corrected the problem.
i have a 02 c240 that i imported from japan, i seem to have similar problems with my car, unfortunately or shall i say fortunately in my country we dont have any emmission laws, so i was thinking of completely removing the catlytic converters, i need to know if the car will still run ok without the CAT... i also suspect the clearing agent put leaded fuel in the tank when he cleared the car from the docks..so far ive only had the "check engine" light come once which i removed it by disconnecting the battery...the light never came on again...but the the cars idling drops at times when i stop at the lights, and this happens spontaneous not always...any help will be appreciated
with an obd scanner you can monitor things like fuel trim, timing, lambda (cat) values etc, its maybe worth buying one (under $100) and see what you find, then you can post on the forums and get more specific info.
I am definately getting one because with a modern car you are in the dark without it.
Just thought, if you get idling problems on modern cars with throttle bodies i.e. anything fuel injected, the throttle flap / butterfly can get sooted up since the smog gear for the oil breathers dump into the intake before the throttle and the oily crap sticks and builds up till it smothers the tiny idle air gap that should exist.
If it revs ok but cuts out on idle its usually an idle control valve (which not all cars have) that is used to prevent run-on when the engine is stopped by cutting the fuel when the power is removed, or it is a gummed up throttle flap in the TB. You can clean it with carb cleaner etc but it must be spotless, then it will run perfect. Done this on a few vw golfs and audis before, the merc will likely be the same.
Dismantling the TB is sometimes awkward but you can just spray the cleaner into it while its connected, just doesnt clean so well, but still works.
You should never disturb the DBW (drive by wire) throttle unit attached to the butterfly on the outside, and using merc obdii software you could do a TB reset, which may clear the fault if it isnt due to sooting but incorrect positional data from the TB
Hey buddy I read the entire thread and was not able to figure out how you or anyone else were able to resolve this problem. On my car the cats were changed last year( 03 C240). So i'm wondering if its the spark plugs or engine mounts? If anyone knows how this problem was solved, please let me know,
So after we changed the plugs and replaced three leaking ignition coils the shaking didn't change so I figured I take it to the dealer. They ran a check and could not find anything wrong with the engine, etc. and determined the problem was with the engine mounts. Their quote was crazy so I am doing it myself (or maybe take it to an indy). I haven't done the change yet, the car doesn't get used that much and I need to find the time and borrow a lift (I read in the repair manual, you have to remove part of the exhaust and might as well do the transmission mount at the same time)....
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