We recently finished swapping a B18B1 from a 97 Integra into our 96 Honda Civic EX (EK Chassis) and everything is working great except that there is a very low idle when you start it. Typically when the engine is cold it would (or should) idle at or around 1,000 RPMs until it warms up. However, when it's cold you have to baby the gas pedal to keep the RPM up until it gets warm enough to idle on its own. When it idles on its own it's idling around 400-500 RPM. We did take the Throttle Body and IACV off of the 96 honda civic and installed both on the B18 motor. Would this cause a low idle issue like this?

I'm still using the ECU from the 96 civic and its harness.

I tried searching for possible causes of the low idle issue, but it's not so straight forward once you've mixed parts and changed the engine. Any help or pointers would be greatly appreciated!

 

Get a '96-97 B18B ECU. Why did you use the Civic T/B and IACV ?

 

I used the civic T/B because the one that was on the 97 Integra donor car was from an automatic and I thought you couldn't use a T/B off an automatic car on a manual transmission car. I've since read that you can use the same throttle body, but that the Integra IACV has a 3 wire connector and the civic IACV has a two-wire connector. I'm going to switch it back tonight and see if it makes any difference. I swapped out the Integra IACV with the civic just to do some troubleshooting to fix this low idle issue. The Integra IACV is definitely pretty dirty and should either be replaced or cleaned, but even switching the T/B and IACV didn't seem to fix anything.

Is it the ECU that's controlling the IACV that's been set from the factory or is it the IACV that comes set from the factory? I'm just at a loss as to why this idle is so low and doesn't behave like a normal idle in the sense that it should be around 1000'ish RPMs when it's cold and only after warming up settling down to 500-800 like normal. it seems to always just stay around 450-500 regardless of the engine temp.