I have a 00 chevy silverado 5.3L, will only idle at 400 and with a/c on it drops farther. I have cleaned the throttle body, changed idle air control, throttle position, cleaned mass air flow, crank sensor, sprayed everywhere for vaccum leaks, fuel pump, fuel pressure reg, any other suggestions? My truck has 165,000 on it and has never given me any problems. I bought it with 20,000 and it has had maintance done on it like clock work. The truck will not throw a code, even though it has died numerous times. I am completely stumped? Any suggestions would be helpful.

 

I am not too familiar with your year.
Don't you have an idle adjustment screw?
Have you tried running seafoam through your vacuum pump?
By means of PCV valve line or other vacuum line?
Try puting a bottle of seafoam in at every fillup too
And also 100 - 200 miles before changing your oil
Put 1/2 a bottle in with your oil

 

Try replacing the TPS. It's not very expensive and easy to get to. My truck had a lot of issues to include idling high and skipping 2nd gear... I suspected alot of other things, but swapped it and all those issues disappeared.

 

1 thought i have is have you ever disconnected the battery for 30 sec.? comp may have a brain fart.

 

or bad pcm.

 

To those that posted suggestions thank you, and to all the answers. I did change tps, disconnecting the battery does not work you need a obdII to clear any codes, and no codes are stored, I have done the sea foam trick, no help, and the one answer i didnt want to hear is the computer suggestion. Question: Is it possible that the a/c compressor is drawing to much? It idles low with out it on but when on it drops really low. The a/c works just fine never had a problem with, it blows cold , and no weird noises. Does the compressor pull power even when it is off?

 

Is the idle air control and idle speed solenoid the same thing in this car? I dont think it is. I think the idle air control screws into the intake, right? There is an idle speed solenoid that screws into the side of the throttle body on the 5.7. Is this what you replaced?

 

it only has an idle air control valve and there is no adjustment on it like the 5.7l the 5.3l are straight injection. and i have changed the idle air. keep the suggestions coming please because i am stuck.

 

I realize you have changed the fuel pressure regulator, and those are about $50. That is still what it sounds like as I have identical 00 5.3, it was low idle, and was the regulator. I would suggest pull the hose off it after it idles for a minute or so, and shutoff, there shouldn't be any gas come out of it, if so the diaphram has a hole in it.

 

i changed regulator already but i will disconnect and make there is no gas just incase i got a deffective part