GM Buick/Oldsmobile/Pontiac/Full-Size 1975-1990 Repair Guide

Fast Idle

Print

Refer to the underhood sticker for all carburetor adjustments. If there is no sticker present, refer to the procedures and illustrations that closely resemble your fuel system. Read all procedures carefully and understand them before performing any adjustments to your vehicle.

ADJUSTMENTS

1975-76 2GC, GE, GV

The fast idle is present on some Oldsmobile 400 V8 engines when the slow idle is adjusted.

  1. Place the fast idle cam follower on the low step of the fast idle cam, against the shoulder of the next higher step.
  2.  
  3. Adjust the fast idle screw to obtain the following specified idle speeds (with transmission in PARK ):

    900 rpm, 350 V8 (non-Calif.)
     
    1000 rpm, 350 V8 (Calif.)
     
    1800 rpm, 400 V8 (where adjustable)
     

  4.  

1975-76 M4MC
  1. On 350 and 455 V8s, place the fast idle cam follower on the lowest step of the fast idle cam against the shoulder of the next highest step. Adjust the fast idle screw to 900 rpm in PARK .
  2.  
  3. On 400 cu. in. V8s, place the cam follower on the highest step of the fast idle cam. Adjust the fast idle screw until the engine is turning 800 rpm in PARK .
  4.  
  5. Reconnect all hoses and install the air cleaner. Disconnect the tach.
  6.  

1977 Models

No fast idle adjustment is necessary, as the fast idle is automatically adjusted when the curb idle is set.

1978-80 Models

The fast idle on all 231 V6 and some 305 V8 engines is automatically set when the curb idle adjustment is made. Refer to the emissions sticker under your vehicle's hood for this specific application.

Prepare the engine and vehicle according to the emissions sticker before proceeding with the steps below.

Buick V8
  1. Set the cam follower on the specified step of the fast idle cam according to the emissions sticker. Disconnect the vacuum hose at the E.G.R. valve on 2-barrel models and plug this.
  2.  
  3. Turn the fast idle screw out until the butterfly valves in the primary throttle boxes are closed. You can see this by looking down into the carburetor; the butterfly valves are at the bottom of the bores.
  4.  
  5. Turn the fast idle screw in to adjust the idle speed to specifications. On 4-barrel models, turn the fast idle screw in until it just contacts the lever, then turn it in an additional three turns. Adjust to specified rpm.
  6.  

Pontiac V8
  1. After making all adjustment preparations according to the emissions sticker, place the transmission in Neutral .
  2.  
  3. Place the cam follower on the specified step of the fast idle cam.
  4.  
  5. Disconnect and plug the E.G.R. vacuum hose, using a golf tee or pencil, at the E.G.R. valve.
  6.  
  7. Adjust the fast idle speed screw to obtain the specified rpm using a tachometer.
  8.  

Oldsmobile V8

Since the carburetor tuning procedures vary by model and component application, the procedure given on the emissions sticker in the engine compartment should be followed.

1981-90 Models

Carburetor adjustment procedures for 1981-90 models vary by model and component application. Follow the procedure on the underhood emissions sticker.

 
label.common.footer.alt.autozoneLogo