Can anyone tell me what might be the problem in this situation? I have been noticed that every time my car in drive, neutral or parked, the rpm gauge keeps going up and down. Today, it made a thudding sound with it.

 

Rough idle?

When was the last time you replaced spark plugs and wires?

Also do you notice the interir lights dimming? If you do, look into your alternator.

 

make sure your air box is attached correctly then star looking for vacuum leaks.

 

could be throttle body gasket, mine did something similar around 140k when it had dried up.

 

I have purchased this car recently and the previous owner had no records of the services. I will be replacing spark plugs and wires. The alternator was replaced recently. Thanks for the Tip.

 

A lot of people on facebook AMG page said it could be vacuum leaks. I sure will check it out tomorrow.

 

I would strongly recommend you recommend cleaning your maf and throttle body. My car would hesitate and buck and idle rough intermittently until I cleaned them. Bought a this pack from Walmart which includes both.

Fixed all my problems, cost about $7.99 and an hour of my time. See my post below with before/after.

https://mbworld.org/forums/c32-amg-c...odies-c55.html

Good luck!

Here's a writeup from U/amgen on an earlier post.

("Front" = direction of the car.)

-Remove the 2 top Mercedes, AMG-covers (with airfilters in one).
-The MAF is located in the back, it holds on with 2 plasticarms in the front
and a "hook" in the back. Remove it by bending it gentle to the back so the 2
plasticarms unhook upwards and jiggle it off.
-Remove the electric connector to the MAF straight out.
-Before removing the "snorkle", remove the venthose on the side of it.
-The snorkle holds on with 2 plastic arms on the TB, on top and bottom. Release the upper arm and gentle bend the snorkle back and it will come off.
-Use a small mirror and you can easy see into the TB.
-Clean all parts! (Spray, wipe off with clean cloth)
-Let them dry for 30 minutes.

On reassembly, check the rubbergaskets that they sit correctly and are clean.
When the snorkle goes back, try to hook the under arm first and snap the top
one last. Reassemble the rest. Check all hoses round the TB. Honk and drive!