Chuging at start up

[Dead Man]

Hey guys . I have an 01 4.8 thats been chuging when i start it up and goes away after a min but it seem sto be getting worse . Any ideas . I have been getting a banks 1 and 2 lien code once in a while but it doesnt run any differant just that damn light comes on .. Thanks in advance

[txarkitekt]

You are not receiving enough fuel. I would check your fuel pressure. Screw on a mechanical fuel pressure gauge to the Schrader valve on your passenger side fuel lines. Check to see what it is when you turn the key to the ON position. If it shoots to about 58 psi and hold steady, then the fuel pump and fuel pressure regulator are fine. If it spikes and then drains back quickly, then you are having an issue with your fuel pressure regulator.

Then start your truck and see what the gauge says. If not 58 psi or close, then your fuel pump is starting to go out. Turn your truck off and check the fuel pressure. If it drains back quickly, then your fuel pressure regulator is bad.

But if your fuel pressure is fine, then the problem is your front O2 sensors on BOTH sides--driver and passenger.

[oleshifty]

02 sensors don't come into play at startup...shouldn't be those.

Pull the vac line off the fuel regulator, see if there is fuel in the hose, if not, it's PROBABLY ok. I would change the fuel filter, can't hurt, is a cheap part, and could lower pressure. Run some seafoam/ your favorite injector cleaner.

[txarkitekt]

02 sensors don't come into play at startup...

Even if the engine is warm?

Pull the vac line off the fuel regulator, see if there is fuel in the hose, if not, it's PROBABLY ok. I would change the fuel filter, can't hurt, is a cheap part, and could lower pressure. Run some seafoam/ your favorite injector cleaner.

More times than not, its your fuel pressure regulator.

+1 for the fuel filter. Its inline, easy to get to and only costs $10...or $18 if you do not have the proper fuel line disconnect tool.

Some people who are crafty can use some small slot head screwdrivers, but $7-$8 for a 4 piece fuel line disconnect setup, you can't go wrong.

[oleshifty]

the fuel filters are threaded in on both sides.... 9.99 at autozone, part number 3504. no disconnect tools needed, just pb blaster and flare wrench.

[txarkitekt]

They are threaded????? Wow. Learn something new EVERYDAY.

[Dead Man]

Thanks guys . it started doing something else today at idle the rpms will drop down to like 200 then pop up to about a grand then level out . Any ideas .

[oleshifty]

sounds like a vacuum/gasket leak. Try spray carb cleaning around the engine/listen for whistles.

If there is a bad gasket/vac leak the idle will spike when carb cleaner hits it.

[oleshifty]

No check engine light?

[Sleaper]

sounds like a vacuum/gasket leak. Try spray carb cleaning around the engine/listen for whistles.

If there is a bad gasket/vac leak the idle will spike when carb cleaner hits it.

+1 Mine does the same thing and I know I've got an intake gasket leaking. Make sure your intake is tightened down and/or replace the gasket.