Tickover Exhaust Noise

[JamS3]

When my car is sat on the drive for example and I'm opening the garage sometimes I can hear a different note in the exhaust noise like the sound getting lower then jumping back up for a fraction of a second.

Its as if the revs drop slightly causing the change in noise. Iv'e also noticed this when the car is sat on tickover and I use the electric window switch, the same noise appears.

Is this normal and does anyone know what causes it?

Cheers

 

[Matt]

Its normal I would say.

Most cars do this when you turn the steering wheel when parked up or if you turn the heater fans on a higher setting.

 

[Aky]

Mine does the same but as I've only just bought it and owned it for a week now I was worried it would be MAF, Coilpack etc. You can watch the revs drop slightly then pick back up again. My tickover is about 750-800rpm then it drops probably a good 50rpm making it burble in the exhaust. As long as its normal that will do me!!

 

[JamS3]

Yeh what Matt says has reminded me on that it does do it also when putting on rear heated windscreen, moving steering wheel left or right etc.

Think it may have something to do with the car using electric power resulting in the enigine revs dropping slightly as a result of the electric being used then a fraction of a secnd later they rise to substitute the power being used.

Sound about right to anyone?

 

[Pete69zx]

JamS3, yeah i would say that sounds spot on, but remember... im no expert! LoL

 

[Backdrifts]

Yeh what Matt says has reminded me on that it does do it also when putting on rear heated windscreen, moving steering wheel left or right etc.

Think it may have something to do with the car using electric power resulting in the enigine revs dropping slightly as a result of the electric being used then a fraction of a secnd later they rise to substitute the power being used.

Sound about right to anyone?

that's exactly right.

 

[S3Rossco]

yep anything electrical, takes a charge and will cos the revs to substitute change..

As for the tick over, that should be automatic choke..

 

[mattyboy199]

I remeber when i had a MK4 astra you turn the air con off & the brake pedal would become more solid (****** terrible really having the two linked together hardly both a safety feature).

Is this on start up ? could just be the auto choak.