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My GMC Sonoma V6 makes a pffting noise when first started. Sound comes from engine compartment and varies with rpms. Goes away after a few minutes of driving/warmup. Sounds like exhaust leak at manifold or head gasket leak. No water in oil, no excess exhaust noise during driving.


   
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There could be a leak at the exhaust manifold. This will normally only happen when first started and will go away after the vehicle warms a bit and the gasket expands. Another place to check would be the exhaust 'donuts' between the manifold and pipe connection. These can wear out and leak as well.
_______________

GM Dealer Technician For 18+ Years
In the automotive industry for 20+


   
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thanks to all for the replies, the overwhelming evidence is the manifold gasket or the donut between the manifold and the exhaust system.


   
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Turn on key in my 1992 Sonoma 4.3 and get nothing


   
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Location: Oregon
how's your battery? Battery connections? Power to underhood fuse panel?

what does "nothing" mean? No dash lights, no power to any part of the vehicle? everything is ok but no engine cranking?


   
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Have lights new battery checked fuses all ok trun key noting


   
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Location: Oregon
Not a lot to the starting circuit for that year. make sure you have good ground to the engine. Power to the solenoid comes from the purple wire from the ignition switch through the neutral safety switch to the starter solenoid. Put a test light on the starter solenoid and see what it does when you turn the ignition switch to start. If the test light lights up then the signal from the ignition switch should be good. Verify the ground at the starter and if it is good then you probably have a bad starter. If the test light doesn't light up you will have to start working your way back up the purple wire to find out where you are loosing power. Ignition switch? neutral safety switch? Corrosion in a connection? Broken wire?


   
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Put test light on solenold is hot with out key on put key on still on


   
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Truck is a 5 speed


   
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