On a very hot day (100 degree temps), the car is running pretty much fine. Water temps, oil temps are all well handled. No problems while underway, boost is solid, throttle response is fine. However, idle is very low, around 500 rpms. This is with or without the AC on. The car never stalls, it just sounds like it's struggling when idling that low. Any ideas?

Atkins stage 2 street port w/3mm seals
stock injectors, stock turbo, M2 ecu

Thanks!

 

what does it normally idle at?

 

Normally idles about 800 rpm out of gear, 1000 rpm when shifted into first. Now that I think about it, the unusual low idle doesn't change at all whether the car is in gear or out.

 

vacuum lower? This isn't uncommon on ported motors

 

Yea vacuum is definitely lower when the idle is down to 500, ~ -10. When the idle is at 800 revs it pulls more vacuum ~ -12 and even more when it's cold idling or in gear @ 1000 rpm.

 

idle shouldn't matter in gear or not if you have the clutch in.

adjust your TPS screw...i had to adjust in summer vs winter on mine...fixed it. but if you can stand the 500 rpm idle...not really a big deal if you are not stalling

 

Agree with previous post that idle speed should not change when gear lever is moved from neutral to first gear. That usually indicates a bad Clutch Switch (open circuit; should close when clutch pedal is depressed). Sometimes the internal spring of the switch breaks... happens sometimes on Miatas. Over on the Miata forum, repair has been successful replacing the internal spring with a ball point pen spring. (Don't know if the RX-7 Clutch Switch is the same as the Miata's, though.)

 

I'll pay more attention to whether the idle RPM climbs when I clutch in, or when I actually put it into gear. Always felt like the latter but I'll double check. If it's the clutch, I will check the switch. Thanks!

 

It's the opposite. Here's the long version...

Two switches inform the PCME (ECU) that the idle control system should be active. One is the Neutral Switch mounted on the transmission, which is open unless the gearshift lever is in neutral, in which case it closes to chassis ground. It connects to PCME terminal 1R. The other switch is the Clutch Switch, which is mounted to the rear of the clutch pedal lever, and is open when the clutch pedal is up, and closed to chassis ground when the pedal is down. It connects to terminal 1Q of the PCME. If either of these switches is closed, idle speed is controlled by the IAC valve (via PCME voltage pulses), assuming your foot is off the accelerator pedal. So in neutral, doesn't matter if your Clutch Switch is working or not; it could be broken open and idle would be fine due to Neutral Switch being closed. But as soon as the gear lever is moved out of neutral, controlling idle speed depends on the Clutch Switch being closed when pedal is depressed since Neutral Switch is now open. If Clutch Switch is still open, there is no idle speed control loop and engine rpm may go up or down *****-nilly.

Cruise control operation will also be affected if the Clutch Switch is bad, particularly if a shift change is attempted with CC ON and the switch stays open with pedal down!