Possible Shutter Valve Problem?
 

I just picked up an '83 GSL 5-Speed. It sat for some time and I'm using it as a daily driver. Well, trying. I'm new to owning an RX7 but not new to rotarys, (I was a tech at a mazda dealer.) but I've never experienced this before.

What happens is, when driving (usually after warmed up) the car will sputter very bad, like it's out of gas. And it usually occurs while driving above 60mph. It runs great around town. Instead of sputtering around at 20 mph, i pull over and shut it off or it stalls and i let it sit for a minute then fire it up, burn the tires, and get going again. Then it runs great for another 10 miles.

The reason I'm suspecting ths shutter valve is beacause it also has a rough idle, cold or warm. I'm going to replace plug wires tonight, plugs are NGK-R's and new, I'm not sure that it would be bad gas because I've put over 500 miles on and ran plenty of gas through it. (Car acts up with full tank or near empty so I doubt its picking up rust or dirt from the bottom of the tank).

Sorry to write so much but I can't get online often unless with my cell phone so I can't reply much. But go ahead and ask questions or give answers.
Thanks for any help.

I may be way off base here, but have you replaced the obvious...like the fuel filter?

DD

Even if the fuel filter has been replaced, it may be time to do so again.
Since you state that it had sat for a while, it likely has some rust in the tank. This will clog a fuel filter rather quickly.
Could also have crud buildup inside the fuel lines or fuel pump.
Remove the fuel line from the carb, and place a container under under it. Turn the key on to activate the fuel pump, and test the fuel flow. It should flow around 1L per minute.

To me it sounds like a crab issue, like the jets may have some rust build up.
But Wulf is right start with the easy stuff and most common first.

If the fuel filter doesnt do it pick up a carb rebuild kit and go at it!

my brothers 85 has the same problem, acts exactly like yours.

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I had the linkage from the coasting valve to my shutter valve break but it didn't fully break and so it would work sometimes and not others. Sorta the same effects your mentioning.

If it's your shutter valve you will have close to zero power when not gunned. However, once you gun it, it should perform well and not be to noticable.
Also it's highly unlikely to only do it around 60mph if it's a shutter valve problem. It will usually do it regardless of speed.
You can usually duplicate a shutter valve problem when the car is parked and you can look into the carb and see it if it's not working properly. Should be able to check your secondaries that way also.
I could be wrong though as I haven't experienced all shutter valve problems. :/
The other problem I had (not sure if this will help but) my secondaries were not always opening (which might have been because of the shutter valve sticking closed and there not being enough vacuum) but anyhow.
I opted to disconnect my shutter valve and make it stay opened, and I also did the mechanical secondaries and it fixed my problems and I actually like it more that way. I also intend to simply remove my shutter valve all together very soon!

I'd say it might be fuel problems but your a mechanic and I would think you would know if it's fuel problems so.

You might wanna floor it though (or run it very hard on the freeway) and see if after a certain time it always does the same thing, which would point to a fuel flow problem which I also had and fixed by getting a new fuel filter (FRAM G4775) which I now change every oil change.

Hope this helps.

Regards,
Orb

Welcome to the forum.
The shutter valve will only affect certain things. One of them be idle quality due to when they fail they create a vacuum leak. You can verify if it is bad by taking the air cleaner top off and listening for a very annoying honking sound. You can also either put your finger or put a bolt in the large hose that comes from the shutter valve and see if it smooths out.
However it is not causing you existing problem.

As others have mentioned the fuel filter is a possiblity.
For the carb I recommend getting a can of Seafoam and putting in the fuel tank with no more than about 1/4 tank of fuel and see if it cleans out the carb. You could have a sticking needle/seat that is shutting off fuel and running the bowls dry. The jets can also be partially clogged with varnish/debri.
It would be a good recommendation to put the new fuel filter on and then perform the fuel volume test also.
If you have a timing light I recommend the next time it acts up to pull over, hook up the timing light and check to see if both the trailing and leading ignitors are firing. Also clean the connections for the ignitors.
These are some very basic troubleshooting tips that are fairly easy to perform and will get you an idea of what is going on.
You could also have a bad coil wire or heavy corrosion inside the towers.

Well im going to replace fuel filter today and ill check fuel pump flow as well. i guess shutter valve is ruled out since my car falls flat on its face at WOT when acting up. time to throw some money into it and hope its an "easy fix".

were going to replace the plug wires, spark plugs, fuel filter and change the oil and coolent. i hope the first three things fix the problem. and im going to give the carb a good clean.

i will let you know if i fix the problem as we have the same deal going on.

Falling flat on it's face at WOT usually points toward a fuel problem. This can be either from insufficant fuel flow to the carb, or a problem inside the carb.
The flow test is the 1st place to start. If the flow is good, then moving to the carb itself would be the next step.
As Doc mentioned, running a can of seafoam fuel system cleaner or berryman B12 in the fuel, about 1/4 tank is best, can really clean out the inside of the carb, as well as the rest of the fuel system. If the jets or internal passages are totally blocked, this may not do the trick. A carb rebuild would be required at that point.

Gasoline left inside a carb too long, can do some evil things.

One more tip I recommend on any car that has been sitting. Add another fuel filter just before the carb. The lines can get a lot of crud build up inside them. This can start breaking loose once the car is put back in service. Adding the extra filter will catch this before it can enter the carb. Using a clear plastic filter at this location will also allow you see whether it has any fuel flowing thru it, as well as how much crud it prevented from getting into the carb.
Keeping a coulpe spare filters in the car is also a good idea.