Rattle at idle

KenMathisHD · April 12, 2020

I've got a 2000 Sierra 1500 with a 5.3, noticed there's a rattling noise coming from a hose that looks like it hooks up to about the middle of the intake manifold on the drivers side. The other end of that hose looks like it goes into the top of the head at the far cab-end of the head on the drivers side]. I know that whatever is rattling is either in or connected to that hose as I can feel it vibrating at the same speed as the rattle and none of the other hoses vibrate. Would this be the hose going to the PCV? Oil was kind of sludgy when I did a change today (hadn't been changed in a few years I'd say), so if that sludge gummed up the PCV then I suppose that might cause it to rattle like I'm hearing, yea? It's occasionally been hard to start (takes a few seconds of cranking to start or you have to crank it over twice), so I figure that would go with having a bad PCV.

CamGTP · April 12, 2020

Yes, that hose goes to the PCV.

Clean the MAF, throttle body and IAC valve too for the hard start stuff. Anything gummed up there could be a cause.

Checking fuel pressure at key on engine off would be a good idea too. It should build up to well over 50psi and not fall much at all for a little bit.

KenMathisHD · April 13, 2020

Where's the hookup for the fuel pressure gauge on this truck? On my Vette it was right before the FPR on the passenger side, right behind the motor. Thinking I need to do fuel filter too since I seem to sometimes get some chatter when the pump primes - is it inline on the NBS, or is it in tank?

CamGTP · April 13, 2020

On the fuel rail itself.

KenMathisHD · April 21, 2020

New PCV fixed the rattling, old one was kinda gunky.

IAC is making an odd noise when going from key on to key off, kind of like a ball bearing being shook around in a small metal cylinder. Noticed it when I was up front checking fuel pressure. Guess that's next on the list.

Fuel pressure got up to about 54psi, then fell to about 50psi within 2 minutes, and then 48 psi after 5 minutes passed. Weird thing I noticed was I had a lot of chatter coming from the fuel rails, and the needle for the pressure gauge would shake a lot when the chatter occurred, like it would go back and forth past 60psi too quickly to follow with my eyes. Once the pump shuts off, pressure immediately goes to 54psi and the chatter quits. Noticed my hard start occurs when it does this, and I don't have an issue starting it when I don't hear any chatter from the lines. I didn't get chatter when I started it cold this time, but I kept getting it afterwards. Relieving the pressure in the lines via the fuel pressure gauge and cycling the pump again so pressure rose from 0 still gave me chatter, though it was delayed very slightly. Does this thing have a fuel pressure regulator, or is there something else that regulates fuel pressure or relieves it after it gets to a certain psi? I'm betting that's where my problem lies.

I replaced the fuel filter prior to testing pressure and the chatter did occur before I replaced the filter. It went on the same way the old one came off.

CamGTP · April 21, 2020

The pressure regulator is on the fuel rail as well. It has a vacuum hose going right to it.

KenMathisHD · April 29, 2020

That was it. Replaced the FPR, no more pressure fluctuation or chatter in the rails, and fixed the hard start issue as well.

Should've seen it, had a bunch of fuel come out of the vacuum line when I pulled it off. Sucker must have been bad for a while. Is there anything I need to do since there was fuel in that vacuum line?