I have a 94' RX7 with a PFC, street port, 99 twins, stock map, apexi intakes, intercooler, and lots of suspension mods.

Here's the problem:

If I rev the engine up to say to 2-3rpms when warm and let off the throttle fast, the RPMs will drop so quickly that sometimes it goes all the way to zero and stalls. Sometimes the ECU catches it and it keeps it running. It happens very often if I am driving slow and push in the clutch that causes the RPMs to drop fast. It also happens at a stop if I were to touch the throttle a bit and it goes up/down it may go all the way down and stop. This only started after I installed the PFC.

I've done the idle learning, cut the right wires before the ecu, and it idles great. It is only this stalling that makes it challenging to drive.

Any idea what it could be? Could I need to tune something on the PFC? Any ideas would be much appreciated.

Thanks,
Chris

 

I do have one idea. I did before the PFC install adjust the primary/secondary butterflies and I may may have too much air bypass. I can just adjusting them a little tomorrow to see if that could be it?

Should I also try turning off the O2 feedback?

 

Check the throttle return dashpot, these fail frequently. You can also try raising your fuel cuts, for instance, if you do not have the stalling problem when your lights are on. We always turn off the O2 feedback, but that will not cause stalling on decel.

 

Dash Pot fails if it does not reduce the throttle closing speed enough that you can actually see it slow down. Closing fast and instantly is a failure.

If it does slow down, then next is setting fuel cut higher (really fuel turn back on point) to at lease 1600 rpm for all 3.
If this does not solve the problem, start opening the air adjusting under the TB counter clockwise in 1/4 turns and or:

I prefer to also set the three idle speeds higher than what the PFC comes set as.
Idle A.E. from 720 to 800.
Idle E/L from 800 to 850.
Idle A/C from 900 to 950 or 1000.

 

Turn car on, go to sensor check, depress clutch and tell me if CLT (Clutch Switch lights up black)
If it doesn't or sometimes lights up, that is your issue. Located above clutch pedal.

 

This totally resolved the problem! I took apart the switch and the spring inside was broken and the plunger wasn't coming all the way out to trigger the switch. I found out the small spring was the exact size of the kind of an ink pen. I pulled apart a pen, replaced the spring, put it all back together, and it works like magic now.

Thanks, sctRota!

 

Just following up to say this fixed my problem too. The spring was broken in the clutch switch (the switch on the clutch pedal nearest the driver). I replaced it with one from a ball point pen and it works perfectly now (and the car never dies on clutch in).