I have a twin turbo 1987.

When I start it up in the morning the idle doesn't remain constant usually it remains arout 1500 rpm untill warm. If I rev the engine the rpms drop to 1200. When warm it runs around 900 rpm. I was hoping somebody would be able to tell me what causes it and a guess on how to fix it.

Thanks!

 

Hmmm, a twin turbo 87? Must be pretty rare. Don't let the Turbo "II" fool you. They're single turbo (unless of course you or someone else has installed a twin turbo system). The II refers to it being the second turbocharged RX-7, with the first turbocharged RX-7s only being available in Japan.



As far as the idle, that's about normal. It's part of the "Accelerated Warm-Up System." Mazda put that in to help cold start emissions. Increased RPM helps light off the first converter, until the main converter reaches operating temp.



Usually, if you start the car in neutral, RPMs will shoot up to 3k, then after about 15 seconds drop down to about 1500, then eventually level off once the engine is warm. Normal idle should be 750 RPM once warm, so I'd go ahead and adjust your idle. There's a screw on the BAC vavle for the T2s that controls idle speed. Of course, make sure to adjust when the engine is warm.



I always start the car in first gear to bypass that initial blip to 3k RPM. I just don't like revving a dead cold engine to 3k RPM, load or no load.