PeachParts Mercedes-Benz Forum - View Single Post - Nobody wants to reply in tech help!>>slight increase in idle

rickg · #4 06-18-2003, 12:34 PM

That's the $64,000 question. I don't know what your car looks like under the hood, but that's where. Lift the hood and start checking that rats-nest of vacuum hoses connected to the the intake manifold. Then work your way out from there. One thing I've done is get a can of good ol WD-40 and give a spurt at all the hose connections and suspicous looking hoses. If the idle speed makes a momentary change, you have at least one of the culprits. This can be either a real fast fix, or a long running nightmare, depending on the complexity of your system.
One thing to bear in mind on these W126's is the vacuum system runs all your heat/air vents. So might try tracing down the main hose to that and temporarily disconnect it and plug it off. Then start the car and see if anything improves. That hose should be either identified on a repair CD if you have one, or do a search on the forum. I know this has been discussed alot.