Hi everyone, I had a problem with my 2000 GMC 1500 with a 5.3 automatic. It has 103000 miles on it and in mint condition. This morning I drove the truck a short distance and shut it down when I parked. About a half hour later when I went to start the engine it first cranked and didn't start. I retried and it started and stalled, it did this 3 times in a row. Then it started with a sluggish low idle, then stalled again. It started right up with a low idle again. I drove out of the parking lot keeping the idle high with the gas pedal and keeping light pressure on the brakes until I was able to get out into traffic. After about 2 miles, I stopped at a traffic light and it was running fine, no issues. I'm a bit nervous something is about to fail. I drove it on a few more errands today and it's been like nothing happened, it's running normal. In 2 weeks I'm driving it on a 1500 mile round trip. Does anyone have an idea where I should start looking? The truck is well maintained, recent plugs, oil and fuel and air filters.The battery is 2 1/2 years old and cranks well. One thing comes to mind, this past week I noticed a whine coming through the speakers and it goes up and down with the engine RPM. It never did that before. That's about the only thing I different I noticed and there has been no changes or modifications to this truck at all, it's pure stock. Thanks for reading

 

Considering the truck cranks just fine, I would say that it's a safe bet that the alternator is charging just fine. Chances are, your intake gaskets are leaking causing low engine vacuum until the engine warms up and the heads expand resealing up those gaskets.

It's a pretty simple fix, but it's not for the faint of heart. Overall it's not hard, but requires some time and tools. If you're not up for it, a shop should be able to help verify if the gaskets are truly bad.

If it were me, chances are I'd ignore it and let the truck warm up before driving it. Fix it when you get home and can find a trusted shop, or plan out your repair accordingly, assuming it's truly the gaskets that are bad.