i have 00 ls integra with a gsr swap i did

with obd2b ls wiring harness

i put a obd2b to obd1 jumper with p72 stock ecu

i been trying to figure this out

i start my car and it runs at 3000K rpm and drops between 1500-3000

if i rev my car or get on the gas hard the rpm tach drops to 0 and then when i let off returns to normal

if i unplug my iac and start my car the idle stays almost consistent at 1500 going up and down about 200rpm and i can plug the iac back in and it will stay running the same

i checked the fitv under the throttle body seemed fine

 

air intake seems to be the focus of the problem to me, maybe a bad map sensor or it doesn't match the P72 specs. Are you running the ls im or the gsr manifold? I say get a hondata take it to the tuner and your problem can b worked out I think.

 

Clean your IACV if you have not done so already.

 

tps and map sensor plugs switched? easy to do and will cause this. also check if the throttle body is staying stuck open.

 

I agree with 4463. I had a 95 coupe with a d15b swap and had the same issues. Cleaned the IACV and presto, problem solved.