try a fuel pressure test and see where it leads you.
>I am having a problem with my 2002 1500 Silverado - 5.3L - V8 - with
>170K miles.
[quoted text clipped - 5 lines]
>whistling sound which I could only hear when the truck was idling.
>Any suggestion where to start diagnosing this problem?.
I'd start searching for a vacuum leak first off.
--scott

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Steve - 12 Feb 2008 15:25 GMT
>>I am having a problem with my 2002 1500 Silverado - 5.3L - V8 - with
>>170K miles.
[quoted text clipped - 8 lines]
> I'd start searching for a vacuum leak first off.
> --scott
I don't know if an 02 GM 5.3 uses a Mass air-flow or a MAP system, but
I've had a bad MAP sensor give exactly that behavior. A vacuum leak
would similarly confuse a MAF system so yeah, I'd say look for a vacuum
leak. A big one- maybe in the PCV hose or the power brake booster. You
can disconnect the power brake booster vacuum line and cap it to rule
out the booster itself- if the truck idles and responds to the throttle,
you found the problem.
xserik - 12 Feb 2008 18:52 GMT
I would say vacuum for sure.
That will explain the whistling sound
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Pete C. - 12 Feb 2008 20:17 GMT
> I would say vacuum for sure.
> That will explain the whistling sound
If it's really whistling, and not the whirring death squeal from a
failing in tank fuel pump. A fuel pressure gauge would confirm a problem
there pretty quickly if it shows barely enough pressure to idle and then
drops significantly when the injector pulse width increases.