just put a new carb on my 69' CADI & when i start the car it stays on high idle,as if some1 putn the pedal 2 the floor


Asked by Mar 17, 2015 at 10:37 PM about the 1969 Cadillac DeVille

Question type: Car Customization

1 Answer


There's 2 idle speed adjustments on the carburetor. The curb idle speed (650 RPM) is on the driver's side of the carburetor and the fast idle speed (1500 RPM) which is on the passenger's side of the carburetor. As the engine warms up does the choke plate open? If not there's a problem with the heat riser system. There's an exhaust crossover passage in the intake manifold. Hot exhaust gasses warm the choke coil so the choke will open and come off of fast idle. There's a small passage in front of the carburetor that frequently becomes clogged. This should have been addressed when the carburetor was replaced. Originally there was also an idle speed up device tied into the Automatic Climate Control System. I'm sure the replacement carburetor is not equipped with this. The climate control system would apply vacuum to the device on the carburetor to speed up the engine to 900 RPM with the air conditioning on. HTH. - Jim

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