BenzMan1

Helo All,

It has been some time since my last post but I do have some issues I need some ideas about. I moved to Louisville Kentucky about 1.5 years ago from New Orleans Louisiana. Recently this winter I noticed that when I put my can in drive it starts to run really rough and hesitates when accelerating. If I slip the car into natural it runs smooth again. After the car warms up the roughness calms down some but it is still abrasive at best. I also have not seen any codes on the information center when starting the car.

Any Suggestions?

GDawgC220

What year is the car, 4 or 6 cyl and mileage?

If its the 4cyl and higher mileage, its going to run a little rougher, mostly true of any 4 cyl. Probably the motor mounts are wearing out, causing extra vibrations to be felt through the car. Overtime, they dry out and stiffen up, therefore not providing a nice cushion between the engine and chassis.

shadowgriffen

O2 Censor.

Whatstheprtnmbr

When is the last time you did some maintenance for replacing the air and fuel filter? Perhaps it just needs some new plugs and wires, a inexpensive choice instead of going to the dealer.
I had some major issues in this area but a code popped up for the air mass and as you mentioned that you did not have any codes which would point in the direction of the above issues.

johnamoss

I'm betting it's your mass air flow; my 4 cyl C220 had similiar symptoms last spring. My 4 cyl ran about as smoothly in cold weather as warm. No check engine light came on. Dealer diagnosed quickly.



'87 300E: sold after 11years @ 230k & still on the road somewhere in rural Tennessee.

'94 C220 with 93k totalled 10/06 by hit & run broadsiding monster truck: not a scratch or bruise for me

GDawgC220

Can you describe rough to us? Does it vibrate violently? RPMs shoot up and down or unstable idle?

I had a bad MAF with my 202 and the RPMs would go up and down on its own, basically revving to try and compensate for "loss of air" so the engine wouldn't stall. Then it would go back down thinking there is enough air. I have a video of that somewhere.

If its rough vibrations you're getting through the cabin, I'm betting its the motor mounts. They're a common issue to wear out and stiffen up so there is no good cushion between the motor and chassis.

It could be a bad o2 sensor, usually a check engine light shows up if that is the case, you would notice a decrease in miles per gallon.

BenzMan1

I'm starting to think MAS as well but my RPM's are steady. I also have not had a service done in about 55,000 miles. It should be ready for the 120,000 mile inspection.
When I say rough I mean that it vibrates loudly when I place it in drive when it it cold. Once it warms up to running temp it smooths out a good bit but it still has some vibration in drive. I slip it into neutural or reverse at any temp and it is smooth.
I am going to change the plugs and oil this weekend. Can some one give some instruction on changing the fuel filters?

GDawgC220

That's quite a while without service. If it smooths out after the car has warmed up and smooths when putting it into neutral, it might be the motor mounts (a common issue like mentioned before). Since it's in neutral, no stress and load is being put onto the engine, so its smooth. But once you got it in drive, it creates stress and load, so it'll vibrate more and if those mounts aren't in good shape (broken or worn out to a stiff state), a lot of that will be transmitted through the chassis and felt throughout the cabin.

The MAF usually results in a check engine light, unstable RPMs. Because its not functioning correctly, the air to fuel mixture will be messed up because it can't read correctly how much airflow there is, giving the unstable idle.

Plugs might help but doubt it. It'll give better gas mileage, better spark but I don't think it has to do with the vibration.

Do a search, I think the fuel filter change has been mentioned. Otherwise, its not too difficult. Its on the rear right, next to the wheel. you'll see a plastic cover, remove that and you'll see the fuel filter. Just need a replacement, clamp the existing hoses so no gasoline leaks then just remove the old unit. Put back in the new one and you should be good to go.

trbo2nr

Yup. That was my problem as well. 5 minutes to change and back on the road.

lilfoxx

Glad to hear someone mention motor mounts, My Mercedes dealer had a free service inspection. I took advantage of it and found out I needed motor mounts, ck valve (what is this) and frt flex disc (what is this)

GDawgC220

The flex disc I believe has to do with the transmission. It has either something to do with the smoothness/roughness felt through the cabin I believe or hard jolts when shifting into gear.