so on my power fc on my s5 tii rx7 i have the decel fuel cut on and i have never had a issue with this till recently. So when i decel the afr’s are supposed to go lean from the fuel cut on decel but i can see that it is not doing that and it will still inject fuel and go rich at times (10.0). i also see on the commander that the injector duty’s aren’t at 0% it’ll pulse from 0 to another number and pulse. sometimes it does this and sometimes it doesn’t. sometimes it’ll pulse and then fix itself and have the fuel cut on decel working again. the car will also start to buck at lower rpm’s cruising. i’m not sure if it’s injecting extra fuel or something else. Any one know what this could be?

 

since its an FC, i'd check the TPS first. if the ecu doesn't see ~zero throttle, it won't cut fuel

 

agreed... you'll start with the tps first. under the sensor check screen youll be looking at vta1 and 2 and make sure they are within spec. we like to take the throttle cable off during this check to be sure its not influencing it at all. once you have the calibration verified then you'll do a "sweep test". slowly and gradually depress the throttle pedal and watch the voltages change. you're looking for the numbers to climb smoothly and not skip around all over the place. if they don't go smooth then you either have a wiring issue or a bad tps.

it could also just be the throttle plate or linkage being a little sticky. just go through it all and clean everything. remove the tps fully and look under to make sure nothing is loose or broken.

 

so i have a fd upper intake with throttle body could it be that the tps is failing? i haven’t had this issue till now. would wiring cause this too?

 

could be the wiring for sure, he TPS's are pretty bullet proof. still start with checking the VTA1 and VTA2 values

 

so i checked on my pfc commander. fully warmed up this was the voltage

closed

fully open

 

i have checked and it is as all in spec and there was no weird voltage jumps

 

could it be something w the clutch switch? Other ecus usually offer the option to inhibit fco in case of clutch pedal pressed, unsure if the PFC would also do this