Need some ideas for rough idle - NO codes, plugs are new I'm trying to avoid a trip to the $tealership. Car has 140K on the odo and is fastidiously maintained... Fuel injector clean up, coil pack issue, rrrelp!

 

How old are the O2 sensors?

If not them, how old are the plug wires?

 

Wires are less than a year and plugs are new - you think the Oxygen sensor may be culprit? They have not been changed...

 

Its better if you can diagnostic the car,, you may have some code CELs,, try to disconnect the battery for 2-3 hours or a night & see

then........

ZAYED,,

 

How new are the plugs? Seems like I've read all too many times on here something like this with new plugs or sensors or wires and the new parts were the culprit. Try some different/the old plugs maybe?

 

O2 sensors are used at idle and they are a normal wear part (and at 10+ years, they should be dead), so they are a prime suspect. When dying, they either produce low voltage and cause the engine to run rich, or they get coated so bad that they can't detect O2 and cause the engine to run lean (in search of more oxygen).

If you have a friend at a smog shop, ask them to check whether it's rich at idle. You don't need the whole smog test, just idle. It should take about two minutes. If it's rich, my guess is it's the sensors. If it's lean, go home, pull the sensors (after it's cooled down), clean them and retest.

 

Thanks Marcus - I'll yank them and check them tonight (time allowing)

 

do you notice any jerkiness from your transmission?

if your o2 sensor is bad, you'll have jerky shifting between 1st and 2nd gear in D-mode if you make a fast start from stand still with your C43.
2nd gear wont engage, you'll have to let go off the accelerator lose speed and then 2nd gear will engage.
I had this prob on my car but us europeans don't have the CEL on our clusters therefore it was difficult to know what the prob was without a codereader.

try your car in D-mode from standstill and see if your transmission is acting strange

 

Off topic - yo bro....where you been ?

 

C43AMG - how goes it! Check your PM.

Marcus, I ordered 02 sensors all around and new MAF. Always appreciate your input. I will apprise progress...and Kowalski yes, sometimes on the symptoms you describe. We'll see what happens once I replace the parts...

Thanks for the help guys!

 

new o2 sensors will cure the jerky shifting, you'll have new performance feel

 

Dunno if I'm looking forward to removing those sensors, but I am looking forward to curing this rough idle This car is hardly abused by any stretch of the word.

 

On a CLK, they look tougher than they really are. The driver's side front is the toughest. That one is done from underneath. The passenger side front is the easiest and is accessed from under the hood. The two secondary sensors are both accessed from underneath, but are both very easy. On an ME 2.8 car (2001 and later), each sensor has a unique plug, so they can’t be mixed up. The plugs may be different on an earlier system.

 

As always guys, many thanks! Are these 02 sensors 22mm?

 

Yes, a 22mm combo will work. I used the combo and an O2 sensor socket.

 

Many thanks to all - esp. MarcusF and Kowalski! The car runs great It was an 'unfun' job. Car idles great and you're right Kowalki, the shift from 1st to 2nd is much smoother...I also replaced the MAF.

Pics of the 02 sensors below...I'm sure you can pick out the ones closest to the manifold, or pre-cat.



Uploaded with ImageShack.us

 

glad we could help bro.
nomore jerky shifting from 1st to 2nd! who could have known what kind of crappy shifting these o2 sensors causes to our cars!
Daem!

 

I am replacing all of the O2 sensors when I install my headers...

 

Glad you finished that nightmare..., in my car i have only "2" O2 sensors in front, is that related of U.S version or somthing..?!?, cause i

brought the car from Japan 3 years ago.......

ZAYED,,

 

Don't know what you have be a US Spec or otherwise since you're in UAE - all I know is you will spend some time removing the driver's side unit. I purchased a KD Tool 02 Sensor kit from Amazon for $40, it had all the sockets I needed.

 

I agree with you about a country's spec., but in generally should any C43 owners got "4" O2 sensors........??

ZAYED,,

 

I have only 2 o2 sensors upfront, yours is the same as mine euro version

 

I concur, Euro versions only have 2

 

Thankss for clear that guys,, i think japan version is almost the same of Euro’s......

ZAYED,,

 

Where did you buy the sensors? Part number?