What is a stock 5.3 suppose to idle at? Mine idles @ 500rpm to 550 rpm. And sometimes it drops down to like 400rpm amd feels like it wants to kill of me. Is this normal or are my cats clogged.

 

Assuming you are talking about your 2005 Silvy? I'd take a look at your TB and get all the carbon cleaned out of it. Also take a look at your plugs and wires. You should get a code if it was your cats...

I'm leaning towards your TB being dirty!!!

 

Stock idle in my 03 tune at operating temp should be ~550 in park/neutral. Should not stumble much below that though.

 

I just cleaned my TB about a monthn ago and my spark plugs only has about 5k miles on them. It is not throwing a code for my cats.

 

FWIW, mine idles fine @ just under 400rpm.

 

I think if the cats were clogged you would be having a few other problems like being a real dog on power. Just off the top of my head you might check the fuel pressure regulator.

 

sometimes it feels like something is holding it back when iam going down the hiway. how would i go about checking my fuel pressure regulator

 

that idle is normal. what is the temperature? how many miles are on it? does it stink like rotten eggs? no? not your cats. have you ever changed your fuel filter? what kind of plugs did you put in it? does it idle ok? does it smoke when you drive? if so, when? are there any codes at all? is your e-brake sticking? you check your regulator with a fuel presure gauge connected to the test port on the passenger side fuel rail with the engine running, pull the vacuum line off and the pressure should jump up about 5-8psi. i doubt it's your regulator. does it knock or ping? that could be a sign of low fuel pressure.

 

Totally normal. Mine used to idle at ~500 rpm and had a light shake. IMO the idle is too low from the factory. After I got my first tune I definitely noticed how much smoother it idled.

 

same here, I set my idle to around 700'ish now and it's perfect