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1994 Chevrolet S10 Blazer Question: Blazer surging

 

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olchevygirl, Palmyra, TN, November 17, 2009, 19:04
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Recently fixed a water leak problem, changed intake gasket,spark plugs,distributer cap, rotor button,plug wires and plenum gasket. Question is why is the truck surging now? It seems to want to take off on its own at times. And RPM meter is jumping just a tad. It didnt do this before what could it be?

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    patrick mannion from Greg Solow's Engine Room, November 17, 2009, 19:11
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    I suspect there is a vacuum leak somewhere or the throttle cable is mis adjusted and the computer is then trying to fight a high idle. Automotive repair shops have a machine that generates an inert non flammable low pressure smoke that looks similar to cigar smoke. The intake manifold is sealed off, and smoke is put into the engines intake manifold. The smoke then fills the engines crankcase and if there are any vacuum leaks from gaskets, hoses, or housing smoke emits from the source of the leak. Some mechanics will use propane or aerosol carburetor cleaner, with the engine running they will spray the cleaner or propane around the intake manifold and vacuum hoses. A leak will cause a "lean mixture" condition, when the flammable fuel (carburetor cleaner or propane) comes in contact with the source of the vacuum leak the engine idle speed will raise as the engine has received "fuel". this method of finding a vacuum leak works but is not recommended as it can easily cause a fire.

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