Let me start out by saying I have a black 2003 Silverado 5.3 single-cab stepside. So it started out with taking anywhere from 5-20 or so seconds for the truck to start when I turn the key. It just keeps turning over until eventually it slugishly starts. Sometimes, however, it barely turns over at all before it starts up. This has been going on off and on for a year or so now. Once it starts up and I am going, it seems to run at lower RPMs and sometimes even idles at or below 0 at stoplights. Sometimes when I am slowing down in the process of making a sharp turn, the truck will die. I thought at first it may be a fuel issue, with not enough fuel getting to the motor. I replaced the fuel filter, and it seemed to help the startup a little bit. I am thinking that if it were the fuel pump it would have completely gone out by now since I have had some of the symptoms for a year or so. I was also thinking maybe a clogged cat, because when I let off the gas, it often sounds/feels almost like a deep bubbly exhaust back pressure(although it is not loud like a backfire). Im not sure if each one of these symptoms is a different problem in itself or if they are all symptoms of one problem. I am uploading a video of my gauges while driving home from work where you can see the low rpms. I will post the link in a subsequent comment, as it is still uploading to youtube.

 

Its hard to say. If you can find someone or a mechaninc with a scanner that shows live data, he can pin point the problem. He could also check the fuel psi at start up. With just key on, it should be at around 56 psi. Dont start guessin with parts as this could cost more than what the problem really is. When you get it goin does it still run sluggish or clear up after a couple of seconds? Has your SES light flashed at all or come on?

 

It doesnt seem too sluggish when its actually driving. Just seems like somethings off. Will it throw codes even if the check engine light isnt on? Here is the video as promised. Not sure if it will help at all.

 

Yeah I would have a good scanner hooked up. Im pretty sure its something electrical. RPM's should not drop below 550.

 

does your speedo show mph or km per hour? cruising 70 mph at 700 rpm ? wow!

 

Yeah it's definately mph!

 

My first thought is the infamous stepper motors in the cluster are bad. There is no way the RPM's are right. We sent my dad's in not too long ago and his was the opposite -it was showing the idle around 2500 rpm and wouldn't drop all the way down when he shut the engine off.
As far as the slow to start thing, I would first clean the throttle body - they are known to carbon up really bad. If that doesn't fix it check fuel pressure and do a leak down test. Your pump may not be holding pressure so it is having to reprime the system before starting. Also pull the vacuum line off the fuel pressure regulator and make sure there isn't any fuel in the line = leaking regulator.

 

one of our work trucks is like that it takes about the same amount of time to start up but without the problems with the rpms droping and dieing thow

the trucks a 2000 3500 reg cab flatbed

the problem with it is that the fuel pump is going bad and it is weak it wont retain the the pressure needed for starting
we havent gotten around to replaceing it yet
also the truck has duals

but i dont get to diagnos what is wrong with trucks that often at work so my input and theorys go by the wayside
anyway good luck on your insue keep us posted on what it was or is or what you find

and yes you trucks computer will store codes even if the light doesnt come on you can get rid of the cel by disconnecting the battery
i would recomend finding a auto parts store that will let you barrow a scanner to pull the codes also while doing that you can delete the codes so you can drive around then see if there are anby codes that may be the same or different
hope this helps

 

I'm wondering if this could be a compression problem?