Sort of what Bill said :
The idle speed on modern fuel injected gasoline engines is by a metered air by pass orifice .
Typically it's a large brass screw with a big slot in it for the screwdriver needed to adjust the idle speed .
If you can locate it , back it out until it comes out in your hand , the thin O-Ring will usually be stiff and if there's any crud or dirt , etc. on the blunt nose if the screw , use brass polish to clean it hospital clean and replace the O-Ring before re inserting it .
I find this to be the problem far more often that leaky / cracked / broken / fallen off vacuum hoses .
DO NOT use any sort of carby cleaner or aerosol lubricant (WD40 etc.) to search out vacuum leaks ! those sprays ALL attack the delicate rubber and plastic parts , causing more leaks .
Use Aerosol brake cleaner , electro - contact cleaner or starting fluid (ether) but be aware that ether is incredibly flammable and a tiny spark will cause a LARGE flash burn right in your face .
The raised idle speed of the AC is usually yet another calibrated air leak , controlled by a relay .
-Nate
Bill wrote :
The idle speed on modern fuel injected gasoline engines is by a metered air by pass orifice .
Typically it's a large brass screw with a big slot in it for the screwdriver needed to adjust the idle speed .
If you can locate it , back it out until it comes out in your hand , the thin O-Ring will usually be stiff and if there's any crud or dirt , etc. on the blunt nose if the screw , use brass polish to clean it hospital clean and replace the O-Ring before re inserting it .
I find this to be the problem far more often that leaky / cracked / broken / fallen off vacuum hoses .
DO NOT use any sort of carby cleaner or aerosol lubricant (WD40 etc.) to search out vacuum leaks ! those sprays ALL attack the delicate rubber and plastic parts , causing more leaks .
Use Aerosol brake cleaner , electro - contact cleaner or starting fluid (ether) but be aware that ether is incredibly flammable and a tiny spark will cause a LARGE flash burn right in your face .
The raised idle speed of the AC is usually yet another calibrated air leak , controlled by a relay .
-Nate
Bill wrote :
I will guess that the economy circuit has an air leak in the vacuum tubing that is used for it. Bill in Oregon
From: diesel_mercedes@yahoogroups.com [mailto: diesel_mercedes@yahoogroups.com ]
Sent: Tuesday, August 11, 2015 12:21 PM
To: diesel_mercedes@yahoogroups.com
Subject: [diesel_mercedes] Idle rough after turning off AC?
Hi ~
I have a 1998 E300
For some time now after running around in hot weather with the AC on, I will park and out of habit with the AC to economy mode (essentially turning it off). As soon as I do this, the idle goes from perfect to rough.
Any thoughts? Anyone experienced the same?
TIA
K
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Posted by: vwnate1@yahoo.com
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