Whine in the bonnet

engines
gasoline
noises

#1

2003 Chev Venture, 93,000 miles, 3.4L engine. Recently hearing a steady medium pitched low level whine from the parts at the fuel line connections to the fuel distribution header/spider during idle. Noise can be heard from inside the car as well as engine compartment. Noise disappears as soon as engine speeds up from idle. What is causing this noise? How can it be fixed?


#2

Fuel distribution header/spider???

If there is a fuel line/injector fault sucking in air somewhere you would have a rough running engine.

I think the noise is from a vacuum leak. Check ALL air intake components including the intake manifold and plenum. Also check for vacuum leaks at the throttle body and air intake starting at the air filter housing. JMHO is all.

I don’t know if it’s possible, but perhaps the noise is from the IAC (Idle Air Control) motor/switch.

I have the same engine but have not had these noises (yet).


#3

it may be a bad idler, tensioner pulley. or it may be bearings starting to go on an alternator or AC pump.

you may have to try to isolate it audibly to pinpoint it.

try starting the car with the ac off.

try starting it with the ac on.

does it do this when after you have run the car and all is warmed up, and shut off briefly then restart?

i guess the easier way to ask is: are there conditions this does NOT make the sound?


#4

I am going to guess along with Roadrunner. I would take a piece of hose (garden hose, vacuum hose - anything), stick one end in my ear and fish the other end around to try to pinpoint the exact location of the noise. That will give you more to go on.


#5

Roadrunner/cappy208/a_amateur: Thanks for the replies. Started diagnosis with the old wooden rod/broom stick, engine point to ear method, to isolate noise to the tubular plenum (and fuel lines) at the fuel line connection points. Definitely there and nowhere else. Only hear when in idle (at curb or decelerate). Can not hear sound on any manifold parts or belt driven modules (AC, alt., etc.). Will check the IAC. Almost as if the fuel return/over pressure control is humming. Temperature does not seem to be related except for maybe 30 seconds to a minute at cold startup. Pic included.


#6

PCV line cracked? (Vacuum) Or is that arrow pointing at something else?

It’s 11:25pm here and pitch black out, will have to wait until wife comes back from babysitting granddaughter tomorrow to have a look at mine.


#7

Can you feel it with your finger?


#8

not that it takes much, but i’m at a loss. however i wish more people would post pictures. you know they are worth a thousand words! yours is priceless.


#9

Given that you can pick up the noise in several different places I would start thinking about an internal component - such as a noisy fuel pump. If your fuel pump were making noise it would likely echo through everything and give noise in many different components. But I would also check the pressure regulator since fuel pump noise can also be created by problems w/ the pressure regulator. I’m not sure why this would quiet down above idle, but its my best guess at the moment.


#10

I agree. Something flaky with the fuel pump. Any noise from the area of the gas tank?


#11

cyberchem,

aa and NYBo mentioned this.

After looking at your pix for the umpteenth time I think you’ve marked the fuel pressure regulator with the arrow I thought may have been to the pvc pipe.

Atleast that’s what my Haynes repair manual shows.

Do you ever have a problem with the ‘bump’ starts? These GMs have what they refer to as a ‘bump’ start where you turn the key to start and release immediately. (There is no long term engine cranking)


#12

Haven’t tried waving a finger at it. No noise in rear. Starting is likely a ‘bump’, cranks till fire after momentary trigger with ignition key. Thought about the fuel pump but no noise in rear. I tend to agree it may be the fuel pressure regulator. How much effort for a shade-tree mekanik (overhualed several engines that way, including replacing the head gasket on the the @#$% Ford 3.8L-6 two times)?


#13

“Thought about the fuel pump but no noise in rear”. You mean you can’t hear the fuel pump priming noise when turning the key to the RUN position? No buzzing sound for a couple of seconds?

If you want to work on this yourself I’d advise you to spend $20 for a Haynes Repair Manual (at almost any automotive store). You find it will pay for itself in short order.

The ‘how to’ replacement procedure and illustration with text tells all and MUCH easier than me typing for the next ten minutes. (I’ve only got two fingers that work on the keyboard).

You could do this alright. Don’t forget to relieve the fuel pressure first.