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Old 10-20-2012, 11:04 AM   #1
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Question High pitched sound before starting up

My '01 Box has been idling rough so I thought I'd take a look and see what's going on. When I turn the ignition key but do not start the car, I hear this high pitched sound like a tiny little alarm going off right near the throttle body. It'll go for about 20 to 40 seconds and then I hear a whirring and clicking sound like something is trying to open or engage. After that goes away rather quickly, it's back to the high pitched alarm sound. The sound never goes away until I start the car, and I can't be sure it's completely gone over the engine noise after I start it up.

I searched all over the boards for others who have had a similar problem but all they came up with the secondary air injection pump. I'm 100% certain the sound is coming from the throttle body area and not the secondary air pump. The pump is on the passenger side of the engine and this sound is coming directly from the middle near the throttle body.

No CEL codes yet and the car drives fine at speed, but the moment I come to a stop and I'm idling, the car will go from around 900 rpms to 650, then back to 900 and so on about every two seconds.

I tried pulling the oil cap off while the car was running and it started to goes a bit in rpms but the amount of suction seemed normal when I put my hand over the mouth of the oil tube.

Any help would be much appreciated!

2001 Boxster - savanna on black
1960 MGA

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Old 10-20-2012, 11:56 AM   #2
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The high pitch noise (whining) most likely is the Secondary Air Pump.

For your bouncing idle try cleaning your throttle body. There are multiple threads on this site that will help you on how to do this, you will have to remove it to clean it properly.

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Old 10-20-2012, 04:59 PM   #3
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bouncing idle

for me the boucing idle was maf, shortly after aos replacement, sometimes recent install of after market air breather cloggs maf as well, once again, not an expert by any means just recently been thru same symptoms. whinning is secondary air pump
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Old 10-20-2012, 06:02 PM   #4
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I decided to clean the throttle body using both Pedro's Garage and Wayne Dempsey's book as references. It only took about 2 hours to do the whole project and that's because I was going slow and had a hellva time getting the lower rubber sleeve back on.

I cleaned the MAF while I was at since it's a 3 minute job once you're in there.

I took the car out to test drive it and got it up to running temp and it ran like a dream. No weird idle fluctuations. I still hear that tiny alarm sound and the other strange clicking/whirring sound but the car is running great now. If I trip a CEL (assuming it's related to the secondary air pump), I'll go after that next.

Sidenote--> The throttle body wasn't as dirty as I thought it was going to be but cleaning that sucker up made a big difference. I used CNC MAF cleaner since that's all I had at the time, but it did a great job. It looks like new on the inside now!

Thanks for the help!
2001 Boxster - savanna on black
1960 MGA

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Old 10-20-2012, 06:48 PM   #5
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2001 Porsche Boxster S
1988 Porsche 928 S4

Last edited by Dave928; 10-20-2012 at 07:00 PM.
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