Q: my 1997 honda civic it has a swap with a d15b7 and it still has the vtec ecu and it idles at 1500 rpm under all condition and when

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my 1997 honda civic it has a swap with a d15b7 and it still has the vtec ecu and it idles at 1500 rpm under all condition and when i rev it, it drops down to normal then goes back up. even sometimes bounces from 2000rpm to 1700 rpm

My car has 244538 miles.
My car has a manual transmission.

The VTEC ECU (OBD-II) is not compatible with the D15B7 engine which is based on OBD-I standards. There is no way to flash re-program your existing ECU to fully "recognize" the older (D15B7) engine. Consequently, if you want to keep the engine, you would have to change out your ECU to the older one that came with the D15B7 engine. Prior to doing that, you could try to adjust the throttle plate and see if that brings the idle speed down. Another possibility is modifications to the idle air control valve and/or passageways. If you want a mechanic to take a look at what you have, and give you some advice, just request a high idle diagnostic and the mechanic will look at what you have and see if there are any other workarounds to resolve the high idle. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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