Idle Control Valve
 

My brother n' law has a 2003 Chevy Silerado 4.8Lwith a 123K on it. It is having starting issues, a low idle to the point of dying, and the classic cylinder misfire code. So replaced the plugs ad wires with not much of a result. So the next step I suggested is to clean the throttle body to remove a bunch of gunk. In the meantime they took it to PepBoys in California, Long Beach (I believe is where they reside). The Master Tech said it could be the Ignition cylinder (Ignition Cyliner? Mabe a module?). That is what the sister n' law told me. I am having my doubts... Is there any way to test it? Also I found out that he truck spins over and over until it cranks, but not all the time. Sometimes it fires right up. When itdoes crank it has a strong gas smell (flooding). I am supecting a bad fuel pressure regulator. Any thoughts or suggestions? Also the Master Tech suggested the Idle Control Valve needs to be replaced. So the typical question from me is where is it located and how do you replace it since I have never replaced 1? Pepboys wants like 4 to 5 hundred dollars to do the work. Sounds like to me they are trying to get them to replace the whole TB.

So it cranks for a long time before it stars up? Or it spins without cranking, then cranks, then starts?

From the 1 time I heard it, I beleive it is spinning over then fires up... I will call and ask him to be sure. What are your thoughts on it?

Did not get to speak with my brother n' law, but his wife said it is trying to crank while spinning over. And he cleaned the TB and it was pretty dirty. They are driving it today and will let me know how it runs...

Well, I'd think poor spark. Check the cap, rotor and plugs. I believe the 4.8L trucks still had a distributor .. The strong gas smell could be poor spark, the long cranking before start could be poor ignition, and the missfire code could also be poor ignition.

Time for a tuneup?

The 03 4.8 has the individual coil packs. Still has cranking issues, but cleaning the TB has stopped the low idle and stalling. Truck runs a lot better, but now the starting issue... Brother n Law is going to clean the MAF next, but I have my doubts. I am going to suggest the ignition module or as my Sister n Law said the ignition Canister? Any other suggestionsout there Truck Forums?

My 99 z-71 had same problem years ago not starting, it was a little valve on the fuel rail that keeps fuel from bleeding back when the truck is shut off!! Just my 2cents, hope this helps.