Vacuum leak how too??

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Old 02-03-07, 04:26 PM
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Vacuum leak how too??

i just purchase a 1986 chevy c10 pickup truck from a friend, how can i test to see if i have a vacuum leak? i try using carb cleaner with no luck, i try closing the mixuter screws and there was no change in the idle, this engine the idle goes up and down and when i press the accelarator slithly it seems to whats to choke and die, what do you recomend for me to check?
thanks!
 
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Old 02-03-07, 09:19 PM
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86 chev stalls

Take the belt off the air pump and see if that helps it.
 
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Old 02-03-07, 09:31 PM
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unless its idling very fast above 950 rpm turning the mixture screws should make a noticable difference in the idle so it may be time for a carb rebuild but it could have other problems also.
 
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Old 02-04-07, 09:08 AM
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check for vac leak

The carb that came on this year did not have idle adj so some one has changed the carb. Good luck
 
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Old 02-04-07, 09:45 AM
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How many miles are on the carburator? The problem could be a worn throttle plate shaft bore on the carburator. One they wear the idle goes buggy and there's nothing you can do about it except to replace the carburator with a new one.

To verify, once the car is warmed up, jiggle the throttle sideways without opening the throttle. If you feel some play and the idle jumps around, then you've found your problem.
 
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Old 02-04-07, 05:12 PM
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all quadrajets had idle mixture adjustment screws they may of been pluged from the factory but would expect they would of already been knocked out on a 20 year old vehicle thats probably seen a carb rebuild before.
 
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Old 02-04-07, 07:31 PM
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A vacuum leak ussually has a hissing sound and could also be a bad power brake booster. How is the brake pedal. If the brake pedal is hard to push or you hear hissing the booster is bad. If you pull the booster vacuum supply and plug the vac supply port and the engine smooths out than know that the booster or vac supply hose is bad.
I should ask why do you think you have a vacuum leak ?
If it is a vac leak when you go full throttle it should run OK and when it idles it should be very rough running.
I agree with bejay that the carb may need to be rebuilt.
 
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Old 02-07-07, 05:57 PM
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the guy put a new carb in it around 2004, the truck has 150k, i will need to try to test the brake booster and i will report back to you guy's asap.
 
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