fasteddy
Web Wheeler
Reged: 01/30/01
Posts: 12707
Loc: Flat Creek, GA
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Re: Idles smoother when pressing brake- vacuum leak?
03/04/12 09:45 PM
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Vac leak is probably in the booster line, most likely at the manifold nipple. The hose gets brittle from the heat because it's near the head, and cracks there. When the brake is applied, it masks the leak. If you listen with a section of vac hose, ear to one end, leak at the other, you should be able to hear it.
You may have water in the fuel tank. Use gas dry or a bottle of rubbing alcohol in the tank to absorb the water, or drain the tank. Stirring up sediment, while possible, is not as likely, since once it's in the filter, it doesn't go away. If it's water, you are stirring it up into the fuel, and it's getting pumped thru the lines to the carb. Water won't burn, so you get bad combustion. It eventually settles back to the bottom of the tank (heavier than fuel), and if it's a small amount, stays below the pickup. To test, go to a parking lot and do some vigorous tank sloshing by swerving around sharply side to side, and see if it runs badly again.
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"If you can't be a good influence, don't worry, you can still be a horrid example."
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