9 times in 10 it's the result of a vacuum leak. It could be the TPS out of adjustment though.
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on top of the upper intake there is a screw. it can be used to adjust idle speed.
It is under the dash at the steering column.
To adjust the idle on a 1994 Mazda RX-7 with a 13B engine, first ensure the engine is fully warmed up. Locate the idle adjustment screw on the throttle body, which typically requires a flathead screwdriver. Turn the screw clockwise to increase idle speed or counterclockwise to decrease it, while monitoring the tachometer to achieve the desired RPM, typically around 800-900 RPM. After adjustment, verify that the idle is stable and recheck if necessary.
the fuel filter is found on the frame rail near the firewall on the drivers side
Mazda's 13B for the 1986-88 RX-7 made 146hp without a turbo and 185hp with a turbo.
alot of us seem to agree that Royal Purple oil does very well in Rotary engines
check your coil, and your distributor, and ditributor cap, along with all wires and connections.
take off black cap at very top off engine on throttle boby.turn left to raise rpm.
Short answer; you don't. I'd ensure that you really have an 88 FC as those models are fuel injected and don't have a carb.
You need to go to www.rx7club.com, join and do a search. You will find all of the answers you need there.
First check for a vacuum leak in the birds-nest of hoses..........after that, replace your Thermo-sensor on the back side of your thermostat housing.