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Rough Idle when engine is cold
I could use some help from my fellow VW drivers. My 1974 Super Beetle
has a rebuilt engine which I installed in 1996. The engine is stock with all hoses and egr connected and working. The car passed smog every 2 years. The problem I am having is that when I start the car in the morning there is hardly an idle. The engine runs very rough even when I give it gas (pushing down on the accelerator pedal). The throttle lever is on the highest step of the stepped cam. As the engine warms up and the choke opens the engine runs smoother and the idle gets stronger. I am guessing that the problem is just a carburetor adjusted incorrectly. Now I know when an engine is cold it needs gas, not air. With the choke plate closed the ratio of air/fuel is mostly fuel. When the choke plate is completely open (vertical) the ratio of air/fuel is now mostly air (or should be). Can my problem be the bypass opened too much and the mixture not enough? I have tried to adjust the carburetor myself but I don't know if I am doing it right. I turn in the mixture screw until it bottoms and then back it out 3 turns. But as soon as the choke is vertical the engine dies. I have to turn out the mixture screw 5 or 6 turrns just to get an idle. I then turn out the mixture screw until I get the fastest idle on my tach. I turn it in until the rpms drop 30 or so and then I start turning in the bypass screw ( which I left flush with the screw opening). The idle speed starts to drop as I turn in the bypass screw. When I get 900 rpm I stop. Is my way of adjusting the carburetor ok? Am I getting a lean mixture or a rich mixture or can I tell without bringing the car to a smog shop and letting a tech hook it up to his machine and measure the hydrocarbon and nitrous oxides emissiona? I did put a piece of cardboard over the carburetor and even with the opening almost completely covered the engine runs perfectly. It only dies when I cover the carburetor completely. I will bring the car to the local VW shop in a few weeks or so but I would like to resolve the poor idle in the morning problem first. Thanks for any input |
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azazel scratch wrote:
> > I could use some help from my fellow VW drivers. My 1974 Super Beetle > has a rebuilt engine which I installed in 1996. The engine is stock > with all hoses and egr connected and working. The car passed smog every > 2 years. The problem I am having is that when I start the car in the > morning there is hardly an idle. The engine runs very rough even when > I give it gas (pushing down on the accelerator pedal). The throttle > lever is on the highest step of the stepped cam. As the engine warms up > and the choke opens the engine runs smoother and the idle gets > stronger. <SNIP> I wonder if you have *too much* choke when stone cold. Start the engine when cold. Manually rotate the stepped cam so that the choke opens somewhat. See if that smooths the idle. If it *does*, loosen the 3 screws on the choke element (rt side) and turn ceramic element to adjust. Speedy Jim http://www.nls.net/mp/volks/ |
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