auto ride control problems 88 t-bird
 

I bought this car from my Dad and finally got it running about 6 months ago. It has a 2.3 turbo. The ARC evidently started working and I was trying out some new tires when it went into ARC. It must have dropped the car almost two inches, drove like it was on rails with no suspension and the tires hit the wheel well on sharp turns. My question is how does this system work so I can diagnose it. It won't always come out of ARC and gives a blinking light on the FIRM indicator. It feels like only some of the shocks return to normal. When I choose the FIRM ride it only seems to drop the car about an inch. This will be great if I can get it fixed. It was cool going down the freeway like a low rider, except for the bumpy ride. Please help, not much on the internet about the ARC.