my block is from a 94-95 LS and the head and everything else is obd2, my car runs fine on a obd2 p75 but has a cel for no secondary o2 and crank position sensor, 99% sure the crank sensor code is because obd2 reads a sensor on the oil pump and obd1 reads it somehow from the distributor

ok so im gona run a obd1 ecu anyways so i dont bother with those. other day i plug in a obd1 p75 with conversion harness and no cel.

starts right up and no cel but, car idles kinda high, 2k ish in 60 degrees then slowly over 5-15sec raises even higher to almost 3k at which point it starts to bounce and idles down to bouncing between 1k and 2k rpms.

eventually when it gets to normal temp after i drive and come to a stop, it bounces a little more then chills out to a normal idle but does it everytime


i did chip the ecu but J1 is not connected and the soldering is good, never had a problem with chipping my own before

 

OBDII IAC owns you.

 

 

ya i had a feeling that has somthing to do with it, but i had a obd2 civic running obd1 ecu before and it idle fine.. ---- there the same valve anyways what the deal

 

so when people make a basemap for a obd2 car that was converted to they usually have to make some kind of adjustments to deal with the iacv? because thinking back on my last 96 civic 1st time i ran it obd1 was with a tuned basemap i downloaded

 

Disconnect the Evap surge solenoid.. that will end your problems. Just unplug the electrical connection.

 

edit: guess that didnt work , car was just already warm when i tried it. must be the iacv

 

its more than just the evap valve

its pretty common to have this problem though with obd2 iacv....

 

Easiest fix is to take off the IAC and put a small piece of hose in the inlet side to throttle it down like an orifice. It worked great on my Civic and an Integra a buddy had.