noise when leaving foot off accelerator

[akz786 0]

its a 1997 VR6 OBD2 ....all is well really ....just a werid noise maybe electric pump? basically when driving if I accelerate then let foot off gas to change gear i hear a whining which start loud then goes soft very quick (not mechanical) kind of sound which seems like its comming from top of engine.

Could this be the aux pump running or a breather pipe blocked?

Any suggestion appreciated.

Thanks

[rigs 0]

Do you mean the sounds happens when you let off the power and roll in gear or when you put your foot on the clutch to change gear and the engine speed slows?

[akz786 0]

Hi no sorry its not dependant on the gear change or clutch as such...even if i am parked in neutral and rev the caras it revs down you hear this whine, or pump like sound although it does not hinder the cars performance in anyway....i initially thought it might be the aux pump running or a breather hose blocked just wanted to know if anyone has experienced this kind of sound.

[rodney 17]

two things dont let off the accelerator

and second is it a belt kinda whine like on a charger or the likes? and not an electrical whine like on the stereo????

[xyber 1]

mine does it, my mates does it, it stops when the engine has warmed up, was a thread about this before and loads of people get the same

sort of a quiet straight cut gears sound

[akz786 0]

RCF - No its not a belt whine more like a pump whine but only noticable from cold once warmer it gets quiter ...

Xyber - so what exactly is this noise? I tried to a search on here could not find anything....is it anything to worry about?

[sticks 0]

hi i also get this when de-pressing the gas pedal,but once fully warmed it goes,sounds like a off tune saxaphone,its a mystery no one still cannot seem to know what it is,

good luck

[akz786 0]

hi i also get this when de-pressing the gas pedal' date='but once fully warmed it goes,sounds like a off tune saxaphone,its a mystery no one still cannot seem to know what it is,

good luck

[/quote']

Thats exactly the sound im on about "like a off tune saxaphone" lol ....well if anyone knows what this is ...would be good to find out, I cant seem to find any info on it here?

thanks

[xyber 1]

RCF - No its not a belt whine more like a pump whine but only noticable from cold once warmer it gets quiter ...

Xyber - so what exactly is this noise? I tried to a search on here could not find anything....is it anything to worry about?

I have a feeling its something to do with the throttle body if I recall whilst the engine is cold, nothing to worry about anyway, ill try and find the post

[tonk 0]

does everyone that 'hears' strange noises have climatronic fitted?

[xyber 1]

It was nagging so did some hunting, (copied and pasted)

Secondary air injection

The ECU electrically pulls a small solenoid valve

open, allowing manifold vacuum to go to a bigger valve

(the combi-valve), which opens a passage from an

electrical air pump to a passage in the head that goes

to the exhaust passages. The ECU also turns the air

pump on and it blows fresh air into the exhaust. This

is in the first 2 minutes or so after a true cold

start. It helps finish burning the rich default

exhaust mixture that is used before the O2 sensor

heats up and the system can go to closed loop

metering. The process of the burn completion also

heats the catalyst faster, resulting in light-off in a

shorter time.

Both valves and the pump are under the intake manifold

behind the radiator. Manifold vacuum comes off a "T"

in the line to the fuel pressure regulator (silver

disc on the fuel rail).

When the car is started and the coolant temperature is

below a certain temperature (80C, I think), the ECU

tests the system by turning it on for a couple of

seconds. This also happens right after the O2 sensor

comes on line after a cold start. Since the O2 is

online, the ECU expects to see at least a 25% leaner

(more oxygen) signal from the O2 (less voltage) while

the pump is running, because it's injecting fresh air

into the exhaust.

Possibilities, in order of likelihood:

1. 50a fuse has corroded and is not longer carrying

current. Check relay/fuse block with relay 111.

Check your air pump gets 12v when the car's cold.

2. Solenoid valve or combi-valve has failed. Air pump

gets 12v and runs but cannot dump air into exhaust

through closed valve. If you can hear your air pump

run this might be the case.

3. Air pump relay has failed.

4. Air pump has failed. From what I hear it makes

nasty bearing noises before it does though.

[akz786 0]

Now thats a good find! so not being stupid but if I am hearing the noise does that mean the air pump is working or the solenoid is stuck asd per point 2? .

"Solenoid valve or combi-valve has failed. Air pump

gets 12v and runs but cannot dump air into exhaust

through closed valve. If you can hear your air pump

run this might be the case."

[sticks 0]

hi tonk yer mine has clima fitted,also cheers xyber for that info.

[xyber 1]

Now thats a good find! so not being stupid but if I am hearing the noise does that mean the air pump is working or the solenoid is stuck asd per point 2? .

"Solenoid valve or combi-valve has failed. Air pump

gets 12v and runs but cannot dump air into exhaust

through closed valve. If you can hear your air pump

run this might be the case."

possibly, but a little air pump will make that noise, if the valve was stuck id expect more of a hiss

[akz786 0]

by the way where exactly is this secondary air pump located? I cant see it ...I hear more of the noise inside the car than outside when the bonnet is popped open.