Strange new noise

Plague Boy

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Jun 24, 2010, 11:30:03 PM6/24/10

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Well. The '92 Sentra has been running fine and I'm hoping to get
another 1-2 years before it completely rusts out and has to be
junked. But it's making a funny noise now.

I first noticed it last weekend, it slipped my mind until I
drove again today. It's a little hard to describe, it's like when
you pull the compression release on a motorcycle, or a cricket-a
trilling cricket, not a chirping cricket. The noise is "outside"
because I only hear it when the windows are open and it has
something to reflect off of.

I *only* notice it when I am decelerating, and it changes
frequency with the RPMs of the engine, not the road speed. If I
depress the clutch, it goes away. If I step on the gas, it goes away.

I guessing it only is noticeable under high engine vacuum. So,
some kind of vacuum leak? Could a loose exhaust cause this kind
of sound? I've had exhaust problems with this car.

I popped the hood and revved the engine and did a quick visual
inspection of the engine compartment. No noise, and no visible
problems.

I will look further, but I'm not sure how to duplicate a sound
that only is noticeable when the motor is driven by the wheels.
Thought somebody here might have a clue to get me in the right
direction.

'92 Nissan Sentra, 1.6L, 5sp man, 177K AC PS PB
--
PB
"I suspect you're an arrogant little pissant who grew up in the
Red Bull generation." - CJW

E. Meyer

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Jun 25, 2010, 10:20:58 AM6/25/10

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On 6/24/10 10:30 PM, in article
xLWdnd1vLtcmv7nR...@earthlink.com, "Plague Boy"
<plagu...@earthlink.net> wrote:

If it still has any of the heat shields around the exhaust pipe, I would
start by checking those. Just give them a tap & see if you get rewarded with
a rattle. Other possibilities are worn accessory belts & bearings in belt
tensioners/ idler pulleys. These tend to show up predictably at certain
engine revs though.

Plague Boy

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Jul 6, 2010, 10:14:37 AM7/6/10

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Yes, there's still one or two of the heat shields on the
exhaust, and yes, they rattle. But this noise is not a rattle.
I'd have to describe it as an "air" kind of noise. It sounds as
if the engine is sucking in air through some kind of
constriction, and it is ONLY noticeable when you are backing off
the gas so the car is compression braking AND mostly when there
is something to reflect the sound back at the passenger compartment.

willshak

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Jul 6, 2010, 5:42:43 PM7/6/10

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Plague Boy wrote the following:

Have you ever had the timing belt changed? You're over 100,000 miles
past the averaged life span of 60,000-70,000 miles. Not that they all go
at those miles.

--

Bill
In Hamptonburgh, NY
In the original Orange County. Est. 1683
To email, remove the double zeroes after @

Plague Boy

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Jul 7, 2010, 12:30:54 AM7/7/10

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I've owned the car 3 years, in which I've put about 3Kmi on it.
The person I bought it from didn't even change the oil, let alone
any other maintenance. I don't have the records, so I don't know
what might have been done prior.

I was under the impression that this engine uses a timing chain,
not a belt.