little issue

[99casst]

hi guys im looking for some advice or even some help. the last week or so i been having issue with fto any how i had take tps, stepper and variable air speed adjuster if your not shore what that last part is its the box on the side inlet plenum on opposite side of throttle body . now i was having a play today and it runs beautifully but issue i am having is it idles at 1 and a bit rpm and when stop at lights it drops to nearly down to 700 - 800 rpm before going back up bouncing down and back to 1 and a bit rpm. now not try new set up when cold but its been starting normally but i have got 2 steppers but one of the is not very good its faulty and i been doing mix match to make one good one lol. also if any help it feels as if it driving down road and the rpm is showing what it idles at it feels like its little jerky hope that made sense. could this possibly be a stepper fault or a incorrect tps reading im thinking personally its not tps as that would probably throw a code or react bad on throttle response. i have had car ideling at 900 but when put back together drive it a bit goes back to high idle

[CJ]

Your idle speed is set very high, let the engine warm up and reduce it down to 750rpm. Let the engine cool down fully and start it up, if it cuts out from cold them the stepper motor is at fault. If not, the TPS calibration may be out, search the forum for 'TPS' and check the workshop manual for the calibration \ test procedure.

CJ

[99casst]

Right a little update. I have re done idel and Its better it keeps a steady rpm but does now suffer from underliad e.g it dips a bit does not really idel higher if it does settles quicker is this sounding more like a stepper fault

[CJ]

If you've set the idle speed at warm and the car cuts out when started from colds, your problem is the stepper.
If the engine doesn't cut out at cold, the problem is TPS (search for how to check tolerances), IAT (try cleaning it with contact cleaner) or some other system.

CJ