How to Adjust VW Idle Speed with a 34 PICT3 Carburetor

This article was co-authored by Hovig Manouchekian and by wikiHow staff writer, Eric McClure. Hovig Manouchekian is an Auto Repair and Design Specialist and the Manager of Funk Brothers Auto, a family-owned business operated since 1925. With over 30 years of experience in the automotive industry, Hovig specializes in the process of auto repair and maintenance. He is also very knowledgeable in common automotive issues and needs including engine repair, battery replacement, and windshield accessory and maintenance. Hovig's knowledge and hard work have contributed to Funk Brothers Auto winning Angie's List Super Service Award for five consecutive years.

This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources.

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When it comes to the old school air-cooled Beetles, the Solex carburetors are notorious for requiring idle adjustments. An appropriate idle speed is essential, since it must remain high enough to prevent engine stalls, but low enough to avoid wasting fuel or putting wear and tear on your engine. In this article, we’ll breakdown how to adjust the 34 PICT3 carburetor to change your idle speed.

• Warm the engine up and keep the choke butterfly valve upright before adjusting your carburetor.
• Adjust the fast idle adjuster screw so that the end of the screw is 0.004 inch (0.10 mm) away from the edge of the stepped cam.
• Use the volume and bypass screws to fine-tune the idle engine speed, and aim to get your engine to idle at 850-900 rpm.

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Idle Screw Adjustment

• Ensure the air cleaner is on when adjusting the carburetor.

Warm the engine up by letting it run for 3-5 minutes. Turn the engine on and let it run for a few minutes. Then, shut the engine off. This will give your carburetor time to smooth out any kinks before you make adjustments. [2] X Research source

• Unscrew the fast idle adjuster screw until it is clear of the stepped cam.
• Screw it back in until it just touches the very bottom of the stepped cam—not on any of the steps themselves.
• Now, screw it in another 1/4 turn. This sets the throttle butterfly open the required 0.004 inch (0.10 mm).
• This screw works with the choke to give a smooth idle on a cold engine.
• As the choke warms in concert with the warming engine, the butterfly valve in the throat of the carburetor opens and the fast idle adjuster moves down the stepped cam, reducing the engine idle speed.

Volume and Bypass Screw Adjustment

• The volume control screw is the smaller of the two adjusting screws. Turn it in very gently until it bottoms. Then, unscrew it exactly 2.5 turns.
• Then, start the engine and adjust the bypass screw again until the idle runs at its highest speed.

• A tachometer is an instrument that measures the working speed of your engine in revolutions per minute (rpm). It's typically on the dashboard next to the speedometer.

Follow step-by-step to optimize performance. "I've been working on VWs for years and have a whole library of repair books. But the step-by-step instructions here for adjusting the 34 PICT carburetor are clearer than anything I've seen. I'm not usually one to follow directions to a T, but this time I did. And you know what? My Beetle is really purring now. I couldn't be happier with how it's running." - Tracy G.

Demystify challenging carburetor adjustments. "Tuning this 34 PICT carburetor was pretty intimidating since I'd never done one before. But the diagrams matching each step really helped me picture what was going on in there. I could actually see the parts you were talking about! Following along carefully, I was able to get through the whole tuning process. And the best part? My Beetle's idling totally smoothly now. Not bad for my first go." - Chask H.

Transfer heavy equipment expertise to light auto repairs. "After years of working on big machinery, I don't know much about small engines. But I was determined to get my VW carburetor adjusted properly. This article gave me the perfect starting point. Following the steps carefully let me put my technical skills to work, even though this was all new to me. I couldn't be more thankful to have these instructions handy." - Allen H.

Achieve smooth and stable idle. "I've had my Beetle for ages but could never get the idle right. It was always sputtering and stalling. But going through the steps here to set the screws properly really made a difference. I took it slow and double-checked everything. Now it's idling smooth as butter at 900 rpm. What a relief to have that fixed up finally!" - Michael K.

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• This is actually the recommended setting for most of the Solex 30-34 PICT-3 models.
• If you can’t achieve these rpm settings, it’s possible that the threads on one of the adjuster screws is stripped. You may also have a damaged hole for the tapered screw, or a damaged needle valve or O-ring.
• If the screws work just fine but the rpm isn’t staying stable, you probably have a vacuum leak and air is leaking the intake manifold.