Vacuum leak?

[diogenes]

My 2006 Mazda5 Touring has two sounds from the center of the dash that might be related or might not.

First, when I lift the throttle, as for a gear change (I have an MT), there's a crackle/crunchy sound, kind of like radio static, but it is there whether the radio is on or off. It is most obvious when the engine is cold and at low speed. Putting the throttle back down makes it go away instantly.

Second, on the freeway, there is sometimes a whistle when the throttle is down that goes away when the throttle is lifted.

Are there any vacuum lines that come through the firewall to the dash?

Could it be leaves in the heater/AC system (I have the auto climate control)?

Anyone experienced anything similar?

 

[Robotazky]

My 2006 Mazda5 Touring has two sounds from the center of the dash that might be related or might not.

First, when I lift the throttle, as for a gear change (I have an MT), there's a crackle/crunchy sound, kind of like radio static, but it is there whether the radio is on or off. It is most obvious when the engine is cold and at low speed. Putting the throttle back down makes it go away instantly. Does the sound last continuously until the throttle pedal is depressed again?

Second, on the freeway, there is sometimes a whistle when the throttle is down that goes away when the throttle is lifted. Where is the whistle coming from? Have you check for cracks in the intake between the air filter and the throttle body? Checked that the air filter cover is tight?

Are there any vacuum lines that come through the firewall to the dash?

Could it be leaves in the heater/AC system (I have the auto climate control)?

Anyone experienced anything similar?

 

[diogenes]

Reply to first question -- no, it lasts a few seconds only.

Reply to second question -- I'll check and get back to you.

Thanks for your help!

 

[flcruising]

There are no vacuum lines that come through the firewall. The climate controls are all electronic.

You say it sounds like radio static, and could it be leaves? Yes, I changed my cabin filter the other day, and there were leaves I had to pull out. Check to see if the sound happens when the ac/heater blower is running and/or the recirculate is on. If you haven't changed your cabin filter, it's worth inspecting in there at least.

 

[diogenes]

I'm beginning to think leaves are the most likely answer, at least to the crunchy, crackly sound on throttle lift. Leaves are coming down fast in my area right now, and the air intake screen below the top edge of the hood gets covered with them. I have cleaned them out several times, and the problem seems to get better -- at least until more leaves build up. I also changed the air filter and reseated the cover (didn't find any obvious leaks or cracks in the intake assembly), and the next step will be to address the cabin filter to see if I find any leaves in there.

The highway whistle has not come back, so perhaps I have fixed that too.