Why My Quadrajet Runs Out of Power?

1. Fuel Delivery Issues

The fact that it runs fine on level ground but falls flat under load (hill climbing or heavy throttle) strongly suggests a fuel delivery restriction.

• Fuel Filter/Lines: Check the carburetor inlet filter (Quadrajets have a small paper filter at the carb inlet). A partially clogged one will starve the engine under load. Also inspect the rubber lines near the tank — they can collapse internally.

• Fuel Pump: Even if pressure looks fine at idle, a weak pump can fail under demand. Test volume by cranking fuel into a container for 30 seconds.

• Tank Sock: The in-tank pickup sock can plug up under heavy draw and then let fuel flow again at idle/low load.

2. Quadrajet Secondary System

You mentioned the secondaries don’t seem to come in. The Quadrajet’s secondary air valves only open when airflow demands it. Common failure points:

• Secondary Lockout Linkage: With the engine cold, the choke lockout can keep secondaries closed. Make sure it’s releasing when warm.

• Air Valve Spring Too Tight: If the spring is over-tightened, the air flaps won’t open, causing it to fall flat when you floor it.

• Secondary Fuel Rods/Hanger: If the secondary metering rods are stuck or misadjusted, you’ll get a lean bog under throttle.

3. TPS and Computer Control

Your Riviera has the CCC (Computer Command Control) Quadrajet. The TPS (throttle position sensor) and mixture control solenoid are part of the carb.

• Disconnecting the TPS gave you high idle/dieseling, which means the computer went into default mode. That suggests the carb and electronics are interacting.

• If the TPS is faulty or misadjusted, it can keep the mixture control solenoid from enriching properly under load, causing lean bogging.

4. Ignition Timing and Advance

Don’t overlook ignition.

• Vacuum Advance: If the diaphragm is ruptured or the hose disconnected, you’ll lose critical advance at part throttle/hills.

• Mechanical Advance: If the weights are stuck, the engine won’t advance timing under load and will feel gutless.

5. Vacuum Leaks

A major vacuum leak may not show much on flat ground but will lean the mixture under load. Check:

• Carb base gasket

• Intake manifold gaskets

• Vacuum hoses to EGR, PCV, brake booster, etc.

 Recommended Next Steps

1. Replace/inspect carb inlet filter and fuel pump output.

2. Verify secondary air flaps move freely with the engine off. Adjust spring tension if too tight.

3. Check secondary metering rods for freedom of movement.

4. Test vacuum and mechanical advance function.

5. Hook a vacuum gauge to manifold vacuum while driving up the hill — a sharp drop indicates restriction (fuel starvation or plugged exhaust).