I recently bought a 1992 Efini RX-7 FD3S Type R and have no previous history on the vehicle. Has 71k miles and compression tested and she's still healthy. Whenever shes idling, she misfires and you can clearly hear it in the exhaust. The mods on the car are HKS dual intake, Blitz BOV, Autometer Boost Gauge, and Trust Exhaust. Since I've had her, I've changed all the fluids, cleaned the throttle body and the sensors and spark plugs and spark plug wires. She also idles a bit high too, around 1200-1300 when cold start and even stays at that when stopped at a red light and warmed up. Sometimes drops down to 800. She runs and drives fine, just an annoying misfire at idle. Vacuum at 18inHg and oil pressure when warm is around 1.5-2 kg/cm2. Could it be a small vacuum leak or something like that? Any advice would help. Thanks.

 

likely a small vacuum leak, yes. check to see if its the stock ecu. if it is, then it may help to clean or replace the o2 sensor as well.

 

It's the stock ECU. I'll go out and buy a new O2 and see if that changes anything. I know the motor was pulled at one point because the body is factory red but the engine bay has been professionally painted gloss black. Maybe it was rebuilt, maybe it wasnt.

 

i would bet its just a small vacuum leak somewhere honestly... the o2 sensor may or may not doing anything. i only suggest it because the stock ecu is sensitive and dramatic when anything is out of parameters.