1991 Integra Ls swap issues

ok i went to a well know place in my area to get a new engine put into my 91 integra. it originally had the b18a1 in it ofcourse and the swapped in the b18b jdm because i guess i was just that lucky. ok should this of been an obd change. problem is my engine heat sensor only warms up when the car is sitting still. and when driving it hits the c as in cold. car seems to run fine. but it does act as if it is cold. when i park it revs to 1500 rpm trying to warm up a fake cold engine. could this be the ecu or could it simply be the sensor. if anyone know what the heck im talking back please reply. or pm me. or email me or something ok. ok.
Mike, um yea.

what year was the engine you swapped in? its warms up during idle then goes to cold when you actually start to drive? i think its just a sensor

It sounds like the Thermostat to me. When sitting at a redlight does the coolant temp needle slowly start to go up, then as soon as you drive it goes back down?
What is happening is that the thermostat is stuck in the open position, this allows the coolant to flow freely through the motor. If it does not close than the motor will not stay up to temp. The heat is transfered out of the coolant through the radiator faster when there is air flow through the radiator, that is why it cools back down when moving.
If you can wait a couple of days I will have a complete "How to" on changing the Thermostat. At the moment I am in Fla on vacation and my pc crashed right before I left so I will have to fix it then I should have the guide up by the 3rd or 4th of January.

Ok its the exact opposit so its weird. and yes i know the fun of changing a thermostat on the b18 motor. its no fun changed it right before swap. oh how i miss the b20a5. but thats the weoird thing. it stays cold. so its weird. otherwise id know the problem. its stays cold. and when i stop it goes back to warm. it seems like the fans arent working but that would mean it would be overheating. so i really dont know whats up. um so it stays cold. or so the gauge says. i mean 2 days after the swap its been working right and then when it gets back down to like 32- degrees it messes up again. but yea any ideas?

Ok its the exact opposit so its weird. and yes i know the fun of changing a thermostat on the b18 motor. its no fun changed it right before swap. oh how i miss the b20a5. but thats the weoird thing. it stays cold. so its weird. otherwise id know the problem. its stays cold. and when i stop it goes back to warm. it seems like the fans arent working but that would mean it would be overheating. so i really dont know whats up. um so it stays cold. or so the gauge says. i mean 2 days after the swap its been working right and then when it gets back down to like 32- degrees it messes up again. but yea any ideas?


Re-read my post, your problem is your thermostat. The thermostat is stuck in the open position so that is why your car cools down when moving. Trust me.

but its not over heating or going anywhere near the half mark. i know what problem ur talking about i had it on the old engine.

if your thermostat is stuck open your engine will stay cold not overheat

but its not over heating or going anywhere near the half mark. i know what problem ur talking about i had it on the old engine.

Ok stay with me here
thermostat stuck in open position = car running COLD when moving.
Replace the thermostat and drain and refill the coolant with honda coolant and your problem will be gone.