To check for vacuum leaks first do a complete visual inspection of all of the hoses. This may require removal of some to examine properly. You can use a vacuum tester on each one and pull a vacuum and watch how long it takes to bleed off. You could plug hoses and see if that improves the idle. The point is there is no one way to do this. If you suspect a vacuum leak you must be very methodical and check everything but first look for the obvious like a hose fell from in front of the motor by the firewall. On an automatic don't forget to check the line to the modulater! A noisy mode switch can be a major vacuum leak. Also make sure that the idle motor is controlling the idle, you can test this by pulling off the plug to the idle motor. If this doesn't affect the idle then it isn't controlling it. All three of the large brass adjusting screws on the air inlet manifold should be LIGHTLY seated closed and the idle micro switch should be working so that at idle it clicks. If the cold start valve was running continously you would be flooding the motor so I don't think the problem is there. Pull the plug on it if you want to convince yourself. David Teitelbaum vin 10757 --- In dmcnews@xxxx, Joe Palatinus <jpalatinus@xxxx> wrote: > >The > >mixture screw is a very sensitive adjustment so if a 1/2 turn isn't > >making a difference you probably have a vacuum leak somewhere (which > >might account for your bad gas mileage) >