Idle noise - 98 V70 AWD

My wife's 98 V70 AWD has recently (last 3-4 months it has become
progressively louder) developed a noise at idle, which stops when the
car is being driven. Initially, this was just while the car was in
"park" and would subside when put in gear. However, over time, it has
become louder and in addition to disappearing when driven, it changed
pitch while shifting from park into gear.

What might be the cause?
Is this something that can be easily fixed at home?

Thank you,
Dave

 

Adjust idle speed away from something at resonance ?

Nick

 

Aha!? And how do you want to do just that in real life? With a
computerised ignition and engine control?

Let us know!

Joerg

 

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Hi Dave,

I think yours is the 5 cylinder engine, similar to my '96 850. I've had the
rubber bend on the vacuum line attached to the alternator end of the inlet
manifold deteriorate (twice) and produce a very loud "trumpet-like" sound as
air is sucked in through a hole. It of course varies with engine load.
It's very hard to see and even harder to replace. Have a poke at it with a
long stick or something while the noise is happening and see if it changes.
It's just below the thermostat housing, and connects to a hard nylon tube
that is part of the crankcase ventilation system.

regards
Barry

 

Perhaps with the OBD programmer ?

Nick