and it takes forever to warm up

it's my kid's car and I'm trying to fix it for him
we just put a JDM B18 in it, but it did the same with the old motor

any ideas?

Thanks!

sounds like there could be a bubble in the coolant system. Clean the IACV with some brake cleaner. Also make sure you dont have any vacuum leaks that could cause the idle to surge. Also you could try tightening the FITV on the back of the intake mani.

Also about it not warming up quick, did you replace the thermostat? It could be stuck open. Just replace it, its only 10 bucks.

same problem in my gsr...InJ3cted just named everything i could possibly think of

try this if you still have the problem of erratic idle let the car warm up then take of the intake. There are two ports in the throttle body. Block the lower port while the rpms are at about 3000 if there is vaccum its your fast idle thermo valve the dealer usually wont sell it separate from the throttle body. took off mine due to the same problem and found plastic piece fully unscrewed so tightened it up car runs great