1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Rattling from the hood

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Old 03-15-21, 12:07 AM
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Rattling from the hood

My car was buzzing from the hood when I removed a hose going to the air filter it stopped the hose I removed is the zip tied one.

I believe it’s the green line


any thoughts?

Last edited by Donell Cart; 03-15-21 at 12:18 AM.
Old 03-15-21, 05:58 AM
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Likely a bad shutter valve. They will fail from time to time and will make noise. Its likely stuck partially open. That or the arm is no longer attached and is rattling.
Old 03-15-21, 12:18 PM
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IF the shutter valve is staying open with the hose as you have it now, you are fine to keep running that way. I just shoved a bolt in the hose to plug it off and have been running that way for awhile.
Old 03-15-21, 08:23 PM
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I'm more worried about your oil metering lines being disconnected and capped off. Are you pre-mixing?

And the shutter valve they're referring to is a butterfly valve in the primary intake runner going to the rear rotor. I believe it closes when you decelerate. It is controlled by a vacuum can and rod, controlled by (I think) 2 hoses, one of which is that fatty you have folded over and ziptied.

This modified manifold has the brass butterfly removed and the vac can replaced with a simple bracket, but you can see where the shutter valve is located (just so you know).



Last edited by Maxwedge; 03-15-21 at 09:18 PM.
Old 03-16-21, 02:39 AM
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Originally Posted by cmnork;[url=tel:12459370
12459370[/url]]IF the shutter valve is staying open with the hose as you have it now, you are fine to keep running that way. I just shoved a bolt in the hose to plug it off and have been running that way for awhile.
Today I had to remove the zip tie(btw I daily the car mostly around cali bay area)because it was causing my oil gauge to spike but as soon as I reconnect the hoses the gas pedal got more firm in a good way and the oil gauge whent back to normal when the hose was disconnected It was easier to press down on the gas pedal but as soon as I released my foot I would feel the instant power loss it would nose dive a little.
Old 03-16-21, 02:50 AM
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Originally Posted by Maxwedge;[url=tel:12459446
12459446[/url]]I'm more worried about your oil metering lines being disconnected and capped off. Are you pre-mixing?

And the shutter valve they're referring to is a butterfly valve in the primary intake runner going to the rear rotor. I believe it closes when you decelerate. It is controlled by a vacuum can and rod, controlled by (I think) 2 hoses, one of which is that fatty you have folded over and ziptied.

This modified manifold has the brass butterfly removed and the vac can replaced with a simple bracket, but you can see where the shutter valve is located (just so you know).

thanks so much for your help I’m going to relay all this info to my mechanic that helps me build the car I just recently picked up the 7 and don’t know a thing about cars kinda the learning as I go type of thing I always though rotarys where cool in a weird way idk maby it’s the brappping noise and this situation puts me in a real spot to get to Learn how to fix my car thank you for helping not break down the whole engine. Hahaha
Old 03-16-21, 03:00 AM
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Originally Posted by mazdaverx713b;[url=tel:12459318
12459318]Likely a bad shutter valve. They will fail from time to time and will make noise. Its likely stuck partially open. That or the arm is no longer attached and is rattling.
thanks for getting back to me first I was literally stressing the f*** out trying to figure that noise out thought I broke a seal and my engine was about to explode So so so grateful It was a shutter valve and nothing internal also will the shutter valve cause the car to idle really rough? It jumps in between 1300rpm to almost 2,000 when the car’s warmed up completely.
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