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Q: Ocassioanl stalling at idle, RPMs fluctuate at idle - 1995 Chevrolet K2500 Suburban

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I have no problem starting the vehicle after it sat for the night, when the engine is still cold. When I drive it, park it for a short while and then get back to continue driving, I would be able to start it right away. However, the truck would turn off as soon as the key is back into the run position. So I have to keep it running for a while, and hold the fuel longer. Then the RPM would start fluctuating a lot and it would continue until I put it in gear. The idling would jump up, then drop down so much that it seems that the vehicle would stall. There are no more problems after I have put it in gear and accelerated. So, it stalls only when I try to start it after it was driven and sat for a short time. During idling, the RPMs would ocassionally go around 2900 and then gradually become normal. The repairs I've done so far include the replacement of the spark plugs, fuel filter and injectors. Also, I had the distributor, fuel pump and coil replaced. All the parts are new. Do you have any idea what might cause the stalling?

You either have a leaking injector that is dripping fuel after you shut off the engine and causing a flooded engine and will cause the hard start and erratic running conditions. You could also have a fuel pressure regulator or purge valve that is leaking. The fuel pressure regulator will need to be tested with a gauge and the purge valve tested with a vacuum pump and hose to see if it is leaking vapors when the engine is off. The purge valve may be leaking too much vapor and would show up after running and shutting it off or after getting fuel. The excessive vapors will flood the engine and cause the hard start or stall, and rough or high idles. If you would like to have this checked, a qualified pro from YourMechanic can come to your car’s location to diagnose the stalling problem and high idle to ensure proper repair.

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