ok this JUST happened on my way home from work...i started hearing this loud humming sound coming from the rx7 and it started getting louder as i got closer to home. And it started ideling a little rough. I finally got her home and i opened the hood. It sounds like this Loud VACCUM humming sound coming from the carburator. I removed the blue air cleaner houseing and the sound got louder. i turned the idle screw and i got her to idle fine at 1k. But that loud humming sound is annoying (i have feelt lately taht the car hasent been as powerful.)...Anyways, i just put in a NEW fuel filter about a week ago and the fuel pump is only like 5 to 6 months old. I know my carb need a rebuild because she is leaking gas by the acceloator pump (i think thats the acc. pump). So any ideas guys...that sound is annoying as hell.....she start up fine in an insatnt...and now she idles ok it judt has this LOUD humming sound coming form what it seems from the carburator. Again my rx7 is a 12A 1982 GS model.

 

there is a small 3/8" nipple slash hose that plugs into the bottom of the air filter, there is an emissions? or soemthing type valve attached to it, I had one go bad years ago, but it was right before I swapped the webers on so I didn't bother to figure out what it was or how to fix, I just jammed a rolled up piece of electrical tape into the hole to stop it up like a cork

I think it has something to do with the air bypass/idlecontrol system.

kenn

 

on the passenger side of the intake manifold back near the firewall is a hose that goes from the "Anti Afterburn Valve #2" to the back of the intake manifold. This hose is prone to cracking and breaking because of the heat from the exhaust. If your emissions equipment is still stock/intact, this hose can cause the problem you're describing.

I would take your air cleaner assembly off and take a battery of digital pictures... either one of us will spot the problem, or at least be able to circle things in paint and say "check this thingy"

Jon

 

holy crap kenn chan your right ...i put my finger over that hole and she shut the hell up...lol that sounded wrong...anywyas um should i plug it up..is that safe??

 

Could be a bad shutter valve.. Search mazdatrix' site for info about it..
If it is, I dont recommend replacing it. Just plug both holes somehow.

 

In the parts car I had, that hole was taped shut with packing tape

 

by the way, your sig is way too big.... WAYYYY too big. Please change it. I'll try and find the actual rule that shows sig size, but I'd just take the mcdumpsters thing out and you should be alright . You know me, always being the nagging moderator..

Jon

 

Check your heynes.. by your description, that sounds like the valve you "have to cap" when you take the air cleaner off and run the car. Just cap it.

Jon

 

sweeet thanks guys!!! you guys ROCK!!!

 

Yup, shutter valve took a ****. Heard one last night. Just plug it with a bolt or something.....It's a worthless pile o' crap.

 

Shutter Valves: I've heard them actually "honk" when letting off the gas. I've replaced mine a few times over the years.

 

Shutter valves are like your appendix: God knows why they're there, and if they screw up, just remove them before they cause any serious trouble.

Jon

 

Exactly, i wasn't sure of the terminology as I always (Its a religion with me) removed the stock carb and threw a weber on. so WTF to call it I wasn't sure. but you don't need it, matter of fact one time when I had to do an emissions test I passed with the thing blocked off so who know WTF it is.

kenn

 

the shutter valve cuts air flow through the carb to the rear rotor on decel, and saves about 3% on your fuel consumption.

that being said, its a pos buggy muddafukkin system and i removed the shutter when i swapped engines this summer. best mod on the planet.. when we bought the car the shutter valve was stuck closed.. and we still thought it was fast. *evil grin*

 

So how do youy remove it? i already plugged it but how do you completely take it off? i haven't checked my haynes manuel which i know i should....but yeah......