dboyrusky

I noticed when im slowing to a stop at the light or something i get this sudden one second engine shake and rpm drop and a second later it corrects it self. So far i cleaned TB and MAF, replaced spark plugs, checked all the visible hoses for leaks.. the only code on OBD2 was P0620 but i think its unrelated. If anyone had this issue before I would appreciate any input on what to look for next

Thanks

C230 Sport Coup

Yup. I had that. Leaking brake booster. As in vacuum leak. pop the hood and see if you hear a hissing sound. the new one will cost you an arm and a leg but you can get a used one cheaply.
The service DVD said you had to remove the whole master cylinder to get to it, but I have my mechanic do it because I thought it would be too difficult for me, but in the end he did not remove the master cylinder, he just pushed everything out of the way. It did require removing the windshield wipers and all the parts around there.
If you do decide to try to purchase a used one, any c class brake booster will do. In typical Mercedes Style the stamp many different part numbers on the brake boosters. none of those part numbers appears in their parts catalog comma as they consider it a assembly and assign it an entirely different part number than what stamped on the part. If you have any questions PM me

dboyrusky

I do hear hissing when engine running coming from EGR valve area, is that where brake booster located?

C230 Sport Coup

? You can't spot it?
Drivers side, goes right through the firewall, attached to master cylinder, near the fuse box and ECU.
http://www.ebay.com/itm/2004-Mercede...RXEWNN&vxp=mtr

dboyrusky

I really cant, all the hoses and everything seems to be intact. How does yours sound when its running, does it sound remotely like hissing when you listen close to EGR? Also, i noticed the 1 sec engine shake and RPM drop is more noticeable when heater is on...