some help isolating an irritating noise

[exdeath]

Have a faint ticking/chirping sound on my 03; seems to be coming from the blower plenum area, but can't seem to find it.

Idlers, pulleys and water pump all recently changed, no noises up front.

Probed around with a pry bar to my ear; blower front and back, all over heads/valve covers, alternator, injectors and rails, PCV, EGR, etc, all sound normal. It doesn't seem to be an internal or mechanical issue. Car runs and sounds fine other than the erratic sound of a cricket tainting what is otherwise a silk smooth beautiful purr.

Car is stock save a recent 2.76 pulley, JLT intake, Amazon SCT tune, BF idlers and Evans waterpump. Sound was present before the mods but it seems to be louder now.

It's a very faint, erratic and irregular but rapid tick/chirp sound that sounds almost identical to lifter tick; a little like a noisy swamp cooler or a cricket (though not nearly as loud) and only seems to appear between 1000-2000 RPM and disappears at higher speeds. Clearly audible from inside the car when holding steady around 1500 RPM. Engine revs smoothly and mean up to red line, performance is fine, sound increases in frequency of ticks with engine RPM but not loudness, then it goes away or is drowned out completely beyond 2000 RPM. It's seems to follow engine RPM within that range of 1000-2000 RPM but very loosely like it's trailing behind it but not directly coupled in any way. Standing on either side. the sound appears to come from the back/center of the engine bay/firewall.

Been checking vacuum lines and solenoids and valves and stuff all around the blower. Latest thing I thought of is EVAP solenoid or some other kind of vacuum/emissions control valve or something....(where is the EVAP solenoid? assuming lower firewall accessible under the car as I can't seem to locate it from the top)

Any thoughts/experiences?

 

[JedWele]

I had that sound but it turned out to be my stock idler pulley's swaped them out for BF replacments and a new belt and it took care of it.

 

[exdeath]

Been reading up on symptoms of the noise patterns (frequency of ticks, uncoupled with engine RPM, only occurs at idle and light cruise under 2k rpm, isn't present immediately when engine is first started cold, seemingly more audible inside the car than outside, etc). I am highly suspect of the EVAP solenoid at this point.

Anyone know where that is located on these cars?

 

[jm@ReischePerf]

Sounds like something on the blower belt which can be very hard to localize. Pulley alignment or idler issue possibly.

 

[2FST4USonicBlue]

Does the noise almost sound like the power steering? I was having the same noise where I was only hearing it really inside the car, took it to a performance shop where they swore it was coming from the snout, so I ordered new bearings took it back to another shop where they replaced my bearings (afterwords they told me there was nothing wrong with my bearings) and are now trying to isolate the noise to take care of it.

 

[exdeath]

Nah it sounds more like a cross between lifter tick and a variable speed cricket chirp, like someone ever so gently tapping on the bottom of a shot glass erratically. It's real light and faint and hard to find, but fairly loud in the car if cruising at 2k or below; you can definately hear something irregular that isn't harmonized with the rest of the engine noises. Annoying pulling up somewhere and hearing it bouncing off a wall or another car sounding like a valve is bad or something, but no trace of the sound from the heads/headers/valve covers, just the steady deeply muffled thumps from the valves working. I've put a pry bar on almost every square inch of the blower and snout and heads/valve covers/exhaust manifolds that I can get to from the top, and nothing matches the odd uneven ticks that I'm hearing from the open ear.

Fuel rails on both sides, also steady regular predictable ticks. This is very irregular and fades in and out and bunches up in random packets and speeds up with engine RPM up to 2k then cuts out or is downed out. tick... tick-tick-tick ... tick-tick.. tick... sounds similar to a squeaky swamp cooler running and making periodic chirping noises, but much softer and higher pitch. When you rev over 2k you can't hear it, but let the revs drop and when it crosses around 2k it comes in rapid then stumbles and slows to the irregular discrete ticks, never changing in volume.

Nothing perceptible at the front of the engine from any of the rotating accessories or related drive items. It sounds like its coming off the firewall somewhere. From inside the car it sounds like its coming from inside or under the dash towards the passenger side. Havent had time to look at it anymore today.

Again, suspecting EVAP purge solenoid, or some kind of solenoid/vacuum device. The frequency of the ticks is in the 6 to 10 hrz range. Still don't even know where to find that, assuming from under the car near where the fuel lines come into the engine bay because I can't see it from the top.

Doesn't seem to be clutch/TOB related, as clutch pedal has no effect on the sound.

Probably get it on a lift tomorrow afternoon with a stethoscope and a comb every square cm and start unplugging solenoids, vacuum lines, etc. till I find it.

No codes or any performance or MPG issues. The sound of the engine itself is silk smooth and is to die for holding it at 6 grand, so I'm ruling out any mechanical causes.