I have a 92 Civic CX with a D15B7 motor. Since I bought it last year, it has idled oddly. While in neutral or with the clutch down, it revs up to about 1500rpm and back down to idle speed rhythmically every two seconds. See my video to hear. While in gear and driving, it does nothing bizarre. Sometimes it will start up fine and will not idle strangely, but after about 1 to 2 minutes, it will begin idling strangely.

- I have replaced the IACV but this did not help.
- I checked all of the pins in the (p06) ECU and they all seem to be connected properly and with the right wires.

The main problem is that occasionally the car will die while driving and will not start again, or sometimes after sitting, it will not start. The engine turns over and sounds as if it has started, but as soon as the key returns to the RUN position, the car dies. Strangely, the engine will continue to run while the key is held in the START position.

If anyone has any ideas about how to fix these problems, please give me some suggestions.

 

I realized when I put the key in and turn it to "II", I do not hear any relay clicks, and I do not hear the fuel pump turning on. Perhaps this is why the motor starts, but shuts off as soon as the key returns from "III" to "II".

I re-soldered the Main Relay as I'd read about, but it didn't solve any problems. Does anyone know what I should try next? The car ran 2 days ago and this has been an intermittent problem since last year.

 

Starts and then dies when you let go of the key is going to be a bad ignition switch. You can confirm that by pulling the hand brake up and watching the BRAKE light on the dash (which is powered from the same circuit that runs the fuel and ignition systems). If the light goes out you aren't getting power from the key switch.

Unsteady idling is often because the cooling system is not full. Take the radiator cap off (engine COLD) and make sure radiator is completely full.

Idle in neutral and unplug the wires on the IACV. The rpm should drop real low and almost stall. Adjust for that condition by turning the air screw in the top of the throttle body (Do not adjust the throttle plate stop screw) If you can't get the idle speed down, find out how excess air is getting into the intake. Air leaking in from anywhere will make it idle high.