obsidian43

Hello all,

Hoping someone could help me with a issue on my 2005 C230 6-speed. When approaching a stop, I like to put the car in neutral and let it roll. During that time my idle dips up and down from about 600-750 rpm. I also noticed occasionally when I clutch and in reverse, it will happen too.

This has been happening for about 5 months since I sold my c43 and purchased the c230. I thought it might be the cold dry air or something but its hit 70 degrees and still the same problem. If anyone has any insight to what the issue is please let me know. I greatly appreciate any advice to where to start.

Thanks!

VVF

Welcome to the forum!

Alternator pulley?
These cars use freewheeling pulleys, and they tend to seize after certain mileage.
On automatics you would hear a loud belt squealing and idle somewhat jumping when switching it in reverse with AC on immediately after startup (higher load on the alternator).
Not sure how to reproduce this with a manual - maybe kind of play with the clutch?

obsidian43

Thanks for the reply! I will check the alternator pulley that you suggested. Do you think the tentioner and idle pulley would be a suspects as well?

VVF

You can def check them while the belt is off, but I don't think they would cause dips in idle.
Sometimes they do get noisy when worn though.

1loyd

- Check the fuel pressure regulator (on injection system @ front top of motor) it has a small rubber vacuum line on it, with the engine running; gently pull off the vacuum hose and hold it about 1/4 inch away from nipple. If you see petrol coming from the nipple on the regulator into the vacuum hose - there's your problem! Replace the fuel pressure regulator and it will run like new!