93 NA auto, engine revs like throttle being blipped when started from cold??

[cloudder]

Hi, not sure this is OK to post here, so if not please delete. I started my 93 Supra NA auto after about 3 months and it started straight away, no issues. But then, without any input from me, the revs to shot to 2000rpm and immediately drops back to about 1400 and repeats this all of the time like someone is blipping the throttle all of the time? I let the car do this for about 5 minutes with no change in the blipping, so switched off and back on, but it still did this. I looked at the exhaust but couldn’t see anything out of the ordinary. To note, the car was put away 3 months ago, without any issues and I haven’t touched the car during this period. Oh, I did drop the car into reverse and held it on the brakes and then the revs sat at a steady 2000 rpm. Any idea what could have happened whilst it sat for those months? Many thanks.

[AC93]

I've had this before on my old one, would do it if sat for a while. Not sure why, but after a decent drive and fresh fuel it always seemed to behave! Assuming the ECU is good and no leaky capacitors or damaged tracks from moisture/age ..seem to be getting alot more common now!