Q: I have an engine with a two barrel carburetor. It appears to me the 2nd barrel isn't opening. When and what opens the second barrel?

asked by on

The truck idles pretty good when the engine is cool. It begins to run rough when up to temperature and is very slow to respond. I've cleaned the inside and outside of the carb with carb cleaner and I've cleaned and replaced vacuum lines and connections. I've also changed plugs and wires. I'm baffled! Thanks for considering my dilemma.

respectfully, Jim Burquist

My car has 200000 miles.
My car has a manual transmission.

Hi there. On two barrow carburetors, there are two ways that they open. The most common way is through engine vacuum. When the vacuum drops to near zero, the secondary throttle valve will open and operate the secondary jets. Other systems have a mechanical throttle that opens as the throttle is pushed down far to the floor. Check the vacuum hose or linkage to the secondary and make sure that its hooked up. If your vehicle has a vacuum line to the carburetor and there is no vacuum leak, then the diaphragm in the carburetor could be split causing the plunger to not function making the accelerator pump fail on the secondary circuit. If you need further assistance with your secondary throttle on your carburetor, then seek out a professional, such as one from Your Mechanic, to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. I have an engine with a two barrel carburetor. It appears to me the 2nd barrel isn't opening. When and what opens the second barrel?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Engine makes a high purring sound and won't turn off when key is taken out.

Hi there. What you are describing if often caused by multiple different mechanical system failures, ranging from an ignition system failure to a damaged ignition lock cylinder or electrical connection. Since you're also experiencing issues with engine smoke, it's probably...

Q: Vehicle won't idle

You either have a major vacuum leak at the hose to the brake booster where it connects to the engine, or the intake gasket. A diagnostic inspection of your stalling condition by a mechanic, like one from YourMechanic, will verify...

Q: Q: Speedometer isn't working

Hi. If your speedometer is not working, and your Check Engine Light this may be a sign that your speedometer sensor has failed. As the speedometer sensor is located in the transmission, underneath the vehicle, I would recommend having the...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...