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Rough Idle in Drive

I've searched this forum up and down and can't seem to find my exact issue. I'm hoping someone can help me out here.

I purchased my 06 C230 sport in December 12. It has around 72K miles. When the car is started it starts fine, engine RPMs after warm up run around 620 with car in Park or Neut. When placed into drive or reverse, engine rpm drops to around 550 and car will shake as if it's trying to die. It doesn't die and as soon as a small amount of pressure is applied to the accelerator to raise rpm above 600 the shake stops. Also, when in reverse, it shakes horribly, again slightly increasing the rpm to around 600 stops the shake.

I've check all under the hood for a vacuum leak, replaced the MAF with a brand new Bosch sensor and there is no CEL showing. I've tried to reset the transmission shifting pattern all to no avail. It just seems like low idle is set to low. Before replacing the MAF, i disconnected the old one for approximately 2 weeks, the shaking smoothed out, but was still there. Once new MAF was installed, the shaking returned to the previous levels.

Any ideas?

Thanks,
Will

Try resetting your throttle. There's a diy if you search. Check your spark plugs too. Replace them with recommended OEM Bosch ones.

I'm also getting a rough idle and a CEL that says "idle too lean bank 1 & 2. Replaced the plugs as they had 102,000 miles on them and still have the same issue. Looked for vacumn leaks and found nothing. What next?

Too Lean is most likely a vaccum leak. Do you have a smoke machine or have access to one? It could also be your MAF but i doubt it.

On car too lean at idle it's time to check O2 sensors. Is the car storing any codes.

In general.

Clean & check MAF
Check plugs & coils (& wires on older M112 models)
Check for vacuum leaks
Check that aircleaner is down tight & sealing on MAF. (also for lean idle car)
Check throttle body actuator for jitter/flutter/oscillation

Codes are P2187 & P2189

P2187 System Too Lean at Idle
P2188 System Too Rich at Idle
P2189 System Too Lean at Idle
P2190 System Too Rich at Idle

No O2 sensor codes. First check that air cleaner is down tight over MAF. This is an endless cause of trouble on the M272.

I've checked and double checked that the air cleaner is down tight. Cleaned the rubber gasket and the ring around the MAF. Idle got better but still not perfect.

I got a can of starter fluid spray and sprayed around to see if I could find the leak that way and ended up getting slight rises in idle speed at a bunch of spots. They were all very slight and did not last long so it's hard to tell anything.

I have been plagued with rough engine idle w203, removed the throttle body a second time for a really thorough clean and inspection.
I decided to have a really good look at all hoses - lo and behold - one of the hoses running into the plastic housing at the back of the TB had a inch cut - not easily visible, this hose is quite fragile in structure (engine has only 50k ).
The net result is air intake not via maf.
The symptom - severe rough idle (especially when hot)- causing engine vibration when idling, slight throttle and no vibration. Engine manage light on and off.
Problem not so bad on cold engine.
Engine now back as new without any expensive parts (all thanks to this forum) :)

My issue seems similar to others. There is little vibration at idle when in Park or Neutral. It increases significantly when i put it in Reverse or Drive. It increases more when I turn the steering left or right to maximum. Upon acceleration car is smooth, gets decent power and pick up. Idles at about 82 rpm and about 68 in P or R. It bothers me so much much that when I stop in traffic or a light I put it in neutral. Mechanic says to change engine mounts? Any suggestions?

Quote:

Originally Posted by Khalid Siddiqi (Post 7324080)

I have the exact same issue. Car is only smooth in drive. Rough in reverse, neutral and park. Reverse is the worst. Also there feels like a heavy knock when the car starts too. I am thinking it could be the spark plugs.

I have the same problem too on my 2006 C230 W203 M272.
I have little vibration at idle and it increases when I have it in drive and reverse and move just slightly. I also experience my rpm surge very slightly as I brake to a stop (not sure if this relates to the vibration). Things I’ve done:

1. Replaced the spark plugs. (Helped steady the rpm a little but did not get rid of rpm surging)

2. Make sure the seal between engine air filter housing and MAF is down all the way. (This helped with rpm tremendously! What a crappy design to have no fasteners. Didn’t get rid of problem completely though)

3. Replace engine/tranny mounts. ( this helped with the vibration and gave me a much smoother ride being that my car is at 104k miles, but it didn’t solve the problem)

My next guess is the flex discs/ u joint and bushing, all on the drive shaft. My suggestion to anyone is check the flex discs first before resorting to the engine mounts because the mounts were a tremendous pain for me. Check the flex discs for cracking in rubber etc. And using a pry tool to bend the flex discs will be a good idea too in order to make sure there are no cracks.

To diagnose it to the engine mounts, only way is to watch the engine as you shift from park/drive/reverse. It should not move up and down Dramatically. Also you can grab the engine and try to rock it side to side (This didn’t really help me but thought I’d include it). Engine should rock back and forth gentlyand steadily. You may be able to tell the mounts are bad if it rocks weird.

let me know what you’ve guys tried or if you want to know how I replaced the engine mounts on the m272 engine. I did not find any good tutorials when I was trying to do it.

Hi Johnny,

Thanks for your post. In my case, it appeared to be a my passenger side engine mount. Removing the undertray I found some oil on it right next to where the mount was. I then used a thick piece of wood on the sump to jack the engine up slightly and take the weight off the engine mounts and car. I put foot firmly on the brake and started the engine and went through the gears. The car was completely smooth again, so I am just working out how best to fit the mount to the car.

I had very large amount of vibration in the car it was not slight like yours.

With your rpm surge, I think it could be because the transmission freeing the engine up when the car rolls to a stop, like when you down shift through a gear.

Hope that helps!

Quote:

Originally Posted by imkaz (Post 7423353)

imkaz, I almost want to think it’s the transmission just downshifting. And that it’s operating normally, however, I can feel the car jerk just slightly when the rpm surges too, and i believe the automatic should be more smoother than that. This doesn’t happen on my 2 other automatic cars.

With the mounts, I’m not sure what engine you have as it might be slightly different, but for the m272:

1. You need to disconnect the battery (it’s recommended to use a memory saver but i didn’t use one)

2. Put car on jack stands. You’ll need jack or hoist to lift engine to relieve pressure off of mounts. Remove 2 front splash shields covering the engine.

3. Take out exhaust (exhaust can get very hot, so do this on cold engine). You can also remove the heat shields that surround the front of the exhaust to help you, it’ll be helpful when you get to the mounts too. They are relatively small pieces that have two fasteners. 1 shield on both sides.

3a. Disconnect wires that lead to the sensors on exhaust on each side And unhook the wires to free it when you lower the exhaust.

3b. Disconnect exhaust from rear rubber exhaust grommet/hangers by using pry tool.

3c. Disconnect exhaust at the flanges in the front. You can spray some penetrating oil to help with removing them. (You should buy new exhaust flange gaskets as well for reinstall.

3d. Remove bolts from mounting bracket in the middle of exhaust.

3e. Exhaust is now removed. Lower exhaust out the way.

4. Remove bolts from mount to subframe and remove bolts from mount to engine. (You may need a ratcheting wrench, but I manage to get to top bolts with just a ratchet. It’ll be tight fit)

5. Use jack and block of wood so there is no metal on metal to lift engine and relieve pressure off of mounts. Do not lift from oil pan.

6. When there is enough clearance from lifting engine up, take out old mount, replace with new mount. There is a small post on mount that needs to line up with the top. You’ll see it.

7. Install is reverse of removal.

You can follow these guidelines. I thought I would’ve needed a ratcheting torx wrenches and torx bits and sockets, but this job did not require any of that for me. Bought the wrenches for nothing. P.s there are torque rating on the bolts to mount and engine and mount to subframe, but I didn’t use a torque wrench. I’ll try and upload a picture of the torque ratings and additional sources of instruction later.

For now, here is one that is helpful. It wasn’t my exact engine but process was near identical.

http://www.mercedesmedic.com/diy-eng...mercedes-benz/

If you are well experienced, I would guess this job can take you 3-4 hours. It took me 6-7 hours. Lol and it was a pain for me. I also recommend using either lemforder or Mercedes parts. I read that lemforder are the oem parts without the Mercedes stamp for the mounts but idk.

Surging in park and reverse at idle

I had same problem with somewhat violent shaking(drive and reverse, would put it in neutral to not shake car) at stop light especially with AC on. I visited a friendly Mercedes mechanic here in Reno, NV. who said, as a kind of hint, that it may need new coils, maybe not now but in the future after I told him that I had 121,000k on it, which isn't much. Sure enough I ordered a set of Beru coils on line, $126, installed them today and no problems. I thought it was AC clutch, transmission etc... $1k to $3k repair, but no, only $126. I need to go back and get the mechanics a 12 pack to keep up the good hints. Cheers I hope this helps a few people.

Quote:

Originally Posted by Hotwell2000 (Post 5122176)

I had same problem, thought it was transmission, AC clutch or who knows? But a Mercedes mechanic a few blocks away said it may need new coils, maybe not now but in the future. I took his hint and put in a new set of coils $126 online and problem fixed for last three days. It threw no error codes or malfunctions, which I thought it would(for coils) but he said not always. I had horrible shaking in reverse and drive at stoplights and would put it in neutral to prevent damage, thought it would be $1K-$6K possibly to fix at dealer. Cheers.

Can anyone help me with what a throttle body is? This symptom sounds just like mine.

Quote:

Originally Posted by peteram (Post 5156788)

This is the same exact problem I have, it feels like it wants to jump forward when in Drive at stop light, and wants to jump back when in reverse. I got some coil packs to see if that works, I just replaced spark plugs, didn't fix the problem.

Quote:

Originally Posted by Michael Ludwig (Post 8134500)