*Sanity check*high rev at start then pulsing idle until warm

[okikuro86]

Alright guys im a bit frustrated that I cant recover my old account and at my engine but im not a noob so PLEASE dont treat me like one.

I just need a sanity check, we all know how we just second guess ourselves and need to bounce our thoughts off each other.

The story: just swapped a new (old engine) into my levin coupe cuz the previous owner blew the head gasket, kept filling with water, then let it sit for a few months. after install she fired her up on first try. set the timing and it sounded good. drove it around a bit and was a bit slugish on the responce but the 4a had been sitting for a while so it was normal. worked that out pretty fast by just driving. she was running a bit hot on both oil and coolant but evened out pretty soon. changed oil and filter again after about two days of long driving, nothing too harsh. responce is good, sounds good, and idles at about 900-1100.

parts: aluminum rad, new water pump, all new silicone vac lines, everything else old original parts on a japanese blue top MAP motor in a japanese Levin coupe in Japan. I put everything stock on this motor including PS, AC, even the stock intake cuz thats what im going for except the rad and lines.

the problem: at start up the idle goes to about 2k - 2.2k rpm, after about 40-60 sec she goes to about 1k-1.1k then starts surging from 900-2.1k for about 3-5 min. then sits at about 1k-1.1k and drives normal... if driven when surging she's a bit jumpy in first and second but drives just fine under throttle. only idle is screwy.
The car is running pretty hot but I have not yet verified temps with my infered thermo yet. oil gauge reads a bit hot but coolant temps sit at norm.
Ive been searching for VAC leakes for two days. im just frustrated and i think im just not thinking straight and not seeing the easy reasonable solution. Ive read lots of post like yoshimitsuspeed's. all is familiar and I'm still just not going to the right place and before i lead myself down a crazy rabit hole I want to get you guys ideas. I know most you guys arent running MAP spec so remember that some things are dif from your MAF system.

Thanks for reading my ramblings and for ANY help you can provide. Help me clear my mind and go at this in a sensible manner. Thanks again.
Eric-

PS- if you need some Jap parts let me know by PM. I'll take care of yah

[okikuro86]

Sorry,

The question: should I be looking at something else before the vac lines? or a specific line?
thanks again!

[yoshimitsuspeed]

Sounds to me like the issue is with your temp sensor or it's circuit. The sensor may be telling the ECU the motor is warm before it's fully warmed up causing the surging when it should just still be idling high.
I'd start there at any rate.

If it's at all jumpy while driving make sure your TPS is in spec.