C280 rough engine only when in gear - PeachParts Mercedes-Benz Forum

#1 08-06-2002, 08:53 PM

Hi hello!

this is my first post... i have a question on a rough idle in my 1998 C280... i have searched the entire forum, and found some similar posts but not exactly the same...

anyway, my engine runs rough as if the idle was too low (idle points to around 600-700) when the car is at a stand still and in gear. however, if i shift the car to park, neutral, or reverse, the engine idles normally. otherwise, whenver i am in "D" and at a stop, the car idles rough and will disappear as soon as i step on the gas, at which point the car's drivability is normal. i haven't seen any temperature-related patterns, although it always happens during the first 15 minutes of driving, and only sometimes happens after that.

can someone plz provide me with a methodical solution to pinpointing this problem? thank you!!!!

car specifics: 1998 C280, about 55k miles, always scheduled maintenance items performed per schedule by dealer

fasthair · #2 08-06-2002, 09:28 PM

Hello

Got to wonder about the motor mounts on this one. The reason is it only does it in drive. When in reverse the engine is torqued over to the other way which would lift the motor off the bad mount. Right side mount is most likely settled and giving you the feeling it is idling rough or missing. When engine speed is increased the harmonics go away which is why you don't feel it anymore. If you have a floor jack put a block of wood on it and jack the engine up just a little bit and see if the vibration/miss goes away. WARNING! Do not jack the engine up to far or the fan can and will hit the shroud. Check that the fan is clear before starting the engine. Also use a big enough block of wood to distribute the weight of the motor without cracking the oil pan. I know it sounds crazy but it could be. I've fixed many rough/missing at idle complaints with nothing more then mounts.

Outside of that it could be a lot of things which can only really be checked out with the proper equipment like scopes and scanners and such. Good luck!

fasthair

#3 08-09-2002, 12:57 AM

hi fasthair!

thank you for your reply!

i tried the method you mentioned of gently lifting up the engine at the oil pan to see if the rough idle (or what i thought was a rough idle problem) went away. i think this worked!! i moved the engine up about 1/2 inch or so (can't really make a realistic guess), but at some point, the vibration that i felt through the car went away.

that was very good advice you gave... is there any final check i can do to absolutely make sure it is a bad engine mount before i go ahead to purchase a new mount?

thanks again!
pikachu

p.s.,,, you believe that it is the forward right side mount that is the culprit?

fasthair · #4 08-09-2002, 02:05 PM

Final check? I think you found your problem. However if you want to confrim it look at the mounts left and right. I think you will find the right mounts upper metal part to be very close to the chassis compared to the left side. I would replace all the mounts if it was my car, both engine and trans mount. But yes I think it is the right mount that has settled and making the vibration.

fasthair

#5 08-12-2002, 12:19 AM

hi, fasthair,,,

can you help me to replace the right side engine mount? i do not know if the space around the engine compartment is as tight in the straight-6 w202's, but in my v6 w202, there doesn't seem to be any access to the engine mount from the top side of the engine.

i can see, from underneath the car, the 13mm screw that holds the bottom of the engine mount to the subframe - that's easy enough to remove. but once that screw is undone, and i lift the engine up a bit, how is the engine mount supposed to come off? there is a thin metal shield that blocks access to the top-side screws. also, the exhaust pipes seem to be too close to this shield to prevent accessing the top side screw to the engine mount.

i tried searching the forum regarding this,,, some post refer to a "engine shock" that needs to come off to get the engine mount... i'm not sure what is an "engine shock."

thank you!

#6 08-12-2002, 05:33 PM

I don't have the answer but thought I would help move your post back onto the 1st post page. Sometimes people don't see your post by the time it hits page 2. p.s. Welcome to the forum!

#7 08-13-2002, 09:42 PM

hi tank! thanks for helping me keep this post visible! ;-)

yes, i'm still looking for a way to remove to get the right side engine mount off,,, this v6 engine is just too wide,, i can't get any access to the top side of the engine mount... do you know who might be able to help me?

-pika!

fasthair · #8 08-16-2002, 01:16 PM

Hello

Sorry for the late response to your cry for help. I sent you an email but the Mail Demon returned it. I have never replaced the mounts on the V6 in the 202 chassis. I was hoping one would come in this week so I could get an idea or some pictures on how to do this. However luck was not with me this week and none called or showed up. Maybe Steve or Gilly will see this and be able to help you. Sorry to have disappointed you but I just don't know how to do this yet. I will try to resend the email to you anyway.

fasthair

#9 08-17-2002, 02:42 AM

Try Stevebfl, if he listed an email. He is a master tech and very good with mb's. Good luck!

Ross190E · #10 08-17-2002, 06:08 AM

This message comes to you from the other side of the world and offers little help with your immediate problem. I hope you get it sorted, but what???!!!! a 1998 M.B. with 55 k on the clock and stuffed engine mount . From one whos looking at upgrading to a C class Im tempted to consider a BMW.!. Good Luck. I replaced an engine mount in my Porsche a year ago and thats done 167000 miles.

mikemover · #11 08-17-2002, 04:50 PM

Hey, anybody that can help out our new member here? I've not worked on one of these either, so I can't be of any assistance.

I'm sure there's a way to get at it...you might need an extra-long extension, or u-joint, or flexible extension...sorry, wish I could be more help.

Mike

ronald_m · #12 08-17-2002, 07:48 PM

Hey donnie our new member needs help

lacombe · #13 10-28-2006, 11:12 AM

My 1998 C280 is showing these same symptoms; vibrating in drive while stopped. It does get better once the car warms up a bit?

I asked the local MB shop for a quote to replace the mounts. They said approx $100 each for L and R mount, $30 for tran mount and $400 in labor! I asked why so much in labor, and they said its because the engine, tran and rear axle has to be aligned very carefully? Not sure what they are aligning? Are there shims or something?

I am quite good with mechanical stuff, and thought I'd try it my self. Does anyone have any advice on replacing these? It does look tight with the V6 taking up most of the compartment. Is there a good manual for this car?

Thanks for any Info.

lacombe · #14 10-29-2006, 04:24 PM

Additionaly, only 80K miles on the car, are the new OEM mounts any better than the originals?

blackmercedes · #15 10-29-2006, 10:18 PM

Quote:

Originally Posted by lacombe

Additionaly, only 80K miles on the car, are the new OEM mounts any better than the originals?

They're worn from age, not mileage. When the car is sitting, the engine rests on the mounts. Cars really do age with time, and often it's harder on them than mileage. The new mounts are pretty much like the old ones (my 98 C230 got new mounts this year too) and will probably last another 8-9 years...