whistling noise around 4000 rpm

[Murph2003]

For about 2 weeks now when im accelerating my engine makes a high pitched whistling noise from about 4000 rpms till it shifts. A friend of mine told me a whistling sound means a vacuum leak but i checked all the vacuum lines that i see and they are all fine...So far i havnt noticed a performance difference besides my 15 mpg that i get but thats been like that since i bought the car...any ideas?

[rixGAphx]

1. I agree with your friend, that a whistling is almost always associated with vacuum on the intake side of the engine.
Though it may not be a leak: Old rear-engine VW bug engines had a built-in whistle-rattle at about 3500-4000 rpm when they ran correctly.

The 3400 doesn't have an endemic whistle IIRC, so something might be loose.
Could even be a mis-installed air filter cover, or other intak plumbing if you've had a CAI or HIA added.
Check that area thoroughly.
Vacuum also goes under the dash, as a part of the HTR/AC controls. Try to locate the exact area of whistling.

2. 15 mpg sucks unless you're even heavier on the stupid pedal than me, which is hard to imagine. :eek:
A vacuum leak would account for this, as the *normal* 'puter settings would produce a lean condition. The O2 sensor would detect this, and tell the FI to inject more fuel to prevent the dreaded too-lean conditions (which runs HOT, burns exhaust valves, and produces excessive NOx).

3. Finally, even an EXHAUST pipe will produce 'vacuum'.
Though the gases are under pressure, a fast-moving gas or fluid in a pipe will produce a low-pressure zone at a small hole in the pipe. This is the same 'venturi effect' that carburetors operated on.
At low flow, there might be a pulse of outward exhaust. At higher flows, it can begin sucking air from the outside INTO the exhaust pipe.
So, a puncture of the exhaust pipe, or possibly a looses exhaust connection closer to the engine might be the cause (though you would probably hear exhaust noise and feel exhaust pressure at lower engine speeds).
Starnager things have happened to GA's :eek:

Good luck.
-Rick

[Themeneea]

could be the belt

[GrandAm95]

if its throwing codes i would take it in to get it check out, or just take it to a garage where u know they wont screw u over and have them check it out

[Murph2003]

Ok well i checked the air box and one of the screws was loose so i tightened that down but still had the noise its after midnight here so thats all im going to check for tonight but will check for other vacuum/exhaust leaks tomorrow... As for the 15 mpg i drive about 50/50 city/highway and im not hard on the throttle although somtimes i like to clean out the fuel injectors but not enough to drop it down to 15 mpg...not sure whats goin on there but ill deal with it...and the computer isnt throwing any codes so i cant even go from that but thanks for the advice


Edit-One more piece of information...from what i can tell the sound is coming from the driver side of the engine compartment if that helps at all...

[WoR]

Well, the belt is over there? Maby its an alternator, a/c pump, power steering pump (if its not 2.3 or 2.4)?