Hey everyone I'm new to this site so I figured I would throw my problem out there. Hopefully someone can help. The vehicle in question is my 2000 Chevy Silverado 1500 5.3L Auto. At intermittent times when I start the truck it turns over but as soon as it does it will shut off. This really has no relation to whether the engine is cold or hot. I can start it up first thing in the morning and it may or may not do this. I can run it for 1/2 hour, turn it off and go inside and when I come right back out it may or may not do it. So far 3 times it has not started up after the second try. It take about 5 mins to starts. But majority of the times the second start does the trick. Now this problem is accompanied with rough idle (very low).

I have also developed a tapping coming from the left side (sitting in driver seat) top to mid region of the engine. Not sure if this has anything to do with it or not. I have always had a slight tap/tick since I got it but it was a very faint and constant one. Now it is louder and non constant. I have a friend who is very mechanically inclined. However he has never been good at diagnostics. He said you figure out what's wrong and ill fix it. He thinks the tapping could be the lifters. My oil pressure is running fine and I have the proper amount of oil.

The truck had been sitting before I bought it 3 months ago. Throttle body was gummed along with some nasty spark plugs. The undercarriage is fairly rusty but motor is not. I am not taking it to a dealer because I do not feel good about being violated lol. So if anyone has any advice I would appreciate it.

Thanks!

 

Lifter noise you will have to just pinpoint if that is it.
My bet on the low idle is fuel pressure regulator needs replaced, probably has a hole in it.

 

Sounds to me electrical or mechanical in that something is shutting down the fuel flow either electrically with a computer malfunction, wiring problem; or mechanical such as the fuel pump is failing.
If there was constant such as a hole in a regulator or a clogged fuel filter, it should be a constant problem at all times.
After you get it running, can you do a sustained wide-open throttle for a few seconds, or does the engine start to miss a bit at WOT?

 

Thanks I think I'm going to try the regulator this week. But yea I can keep a constant with no problem. I have only experienced rough idle once and that was in reverse. The fuel pump operates just as it should and I replaced filter about a month or two ago. As well as spark plugs because I was having a bad misfire issue. They were just gummed up pretty bad. Along with the throttle body. The truck sat for a good little while before I bought it a few months ago.