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PostPosted: Mon Jun 08, 2015 11:04 am 
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Joined: Sun Dec 11, 2011 10:55 pm
Posts: 83
Location: Westport, CT
Electronic hum coming from the throttle body motor when the ignition switch is turned on and the car is in gear. Goes away in neutral. I hear it before the engine is started - not sure if it is there with the engine running. Does this sound like a throttle motor going bad??? Think I can trust the old "if it ain't broke don't fix it" approach, or do I need to get on this before I get stranded somewhere?
Too bad the 350 doesn't use the bulletproof throttle body and linkage on my old 280ZX!!!!

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1980 280ZX 2+2
2003 350z Touring
2005 350Z Touring - Silverstone Gray
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PostPosted: Mon Jun 22, 2015 11:46 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
Posts: 14779
Location: CT
Wow, that almost defies physics, doesn't it? Goes away in neutral?!

Have you 100% isolated it to the throttle body motor? Can you use the screwdriver-to-the-ear thing and specifically guarantee it's coming from there?

And your gearbox is standard, right?

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PostPosted: Tue Jun 23, 2015 12:42 pm 
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Joined: Sun Dec 11, 2011 10:55 pm
Posts: 83
Location: Westport, CT
I used a stethoscope probe to isolate the source. Definitely the throttle motor, and the car is manual. Found a thread on the 350Z club that had several sources indicating that this is "normal" on the 350. Sounded less normal and more like a voltage leak to me. Anyway, let's hope the other guys are correct. Yet another indication of how ridiculously complex these cars have become.

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2003 350z Touring
2005 350Z Touring - Silverstone Gray
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PostPosted: Tue Jun 23, 2015 2:43 pm 
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Joined: Wed Apr 09, 2008 5:53 pm
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Location: CT
Hmmm.... I understand all is well and you don't have a problem, but I find it fascinating that it only does it while in-gear. Do you know why it hums in the first place? I mean, what's it doing when it makes that noise, which it doesn't have to do in neutral?
Just curious.

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PostPosted: Fri Jun 26, 2015 2:12 pm 
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Joined: Sun Dec 11, 2011 10:55 pm
Posts: 83
Location: Westport, CT
And the answer is............................

The throttle body is controlled from the ECU by a PWM - Pulse Width Modulation - a signal that can emit a high frequency noise in electric motors.

Normal and just another thing to go bad one day.

Wish it used my 280's lever linkage instead! Operated more smoothly - deadly reliable.

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1980 280ZX 2+2
2003 350z Touring
2005 350Z Touring - Silverstone Gray
CT plate PHILSZ


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