Question about front-end sound

Why might a car make a high pitched howling sound when you let it coast with your foot off the gas, but then it goes away when you get back on the throttle?

-This is only noticeable at speeds > 20MPH. or < 55MPH.

-Doesn’t matter what gear the car is in

-Doesn’t matter if the trans is in neutral or in final drive

-Doesn’t matter if the engine is even running or not.

Has anyone experienced this with their vehicles? It’s a 99 Accord with 136k, Auto.

Leaky/loose intake ductwork?
Vacuum leak?
Perhaps tires?

When you take your foot off the throttle the cylinders and the passages that feed them go into a state of high vacuum. The pistons are still trying to draw in the same amount of air but the passage is blocked by the throttle plate.

But I’m admittedly confused…how can you put your foot back on the gas without the engine running?

Well when the engine is running, you can make the sound go away by getting back on the throttle.

But with the car coasting with the engine shut down, the sound is still there and you just can’t do anything about it.

If the sound is there with the engine off the sound is not coming from the engine.

Is there any oil in the differential?

I hope so,

The car was just up in the air last week for an oil change. I take my car to a good neighborhood mechanic so one would think he would have noticed this if it was a problem.

Wouldn’t the D-rential have been ruined if it was low on oil ?

I mentioned this issue to my mech. one day and he vaguely mentioned the differential but mainly said not to worry about the noise.

It’s nothing I can’t live with and honestly it’s the only issue i’ve had with the car.

With this added info I’d be inclined to start by looking at the intake ductwork for a loose connection and to the wheel well liners, splash shields, etc.

I’m also still wondering about the tires. Does turning the wheel affect the sound? I know I’m thinking wierd, but, then, this is a wierd problem.

No, the sound doesn’t get worse with side-loading on the vehicle like it would if it was a bad wheel bearing.

If it was the tires, why does the sound go away when I put my foot back on the gas?

Because the tread is loaded differently. Does the tread show any evidence of scalloping, cupping, or feathering? Any abnornal wear signs at all?

Realize that tires are just one idea that could fit your symptoms.

The car actually pulls to the left after a recent alignment due to “radial pull” on the front tires.

Any connection?


Thanks TSMB so far, you’ve been more than helpful.