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Strange new noise

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

Reply to
Plague Boy
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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.

Reply to
E. Meyer

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.

Reply to
Plague Boy

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.

Reply to
willshak

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.

Reply to
Plague Boy

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