I own a 98 civic hatchback dx. It hasn't been driven for a while, maybe about 5-6 months. Today I drive it back from where it was sitting. I noticed when it idles only in Park and Neutral the RPM is unstable, when in drive gears the RPM is fine. The engine revs upfor asecond then goes back down the next second. There isn't anything wrong with the spark plugs and I knowthat isn'tthe problem. I've heard it has something to do with "surge" ? Can anyone help please? Thanks!

 

Forgot to mention the car is an AUTO.

 

Could just be stale gas, or the ECU needs to retune itself. Drive it until almost empty, put in 2 or 3 gallons, repeat, and see if it calms down.

 

I asked 2 ofmy friends and both of them said to reset the ECU by unpluggin the negative terminal on the battery and pumping the brakes a few times, and headlight switch. I did that, and it didn't work.

 

Anyone else have suggestions? I just went and put some Marvel Mystery oil in the tank and got a full tank of premium gas. Hopefully the wierd idle will stop. Need help!

 

Umm... what's with the brake pumping thing? To reset the ecu, you just have to disconnect the battery for a few minutes, reconnect it, and let the car run for a little bit. Anyway, I think getting new gas should help it a bit.

 

It may idle strange for a while after resetting the ECU. If the battery ran down while the car was parked, it reset itself then too. So don't reset again.

 

Yea I might just need to drive it a bit more and if the idle is still unstable after this tank I'll take it to a shop. It could be the idle air control value that's causing this problem, or sensor...Thanks for the replies! More suggestions are welcome!

 

Im having the same problem on my 94, I know how you feel and what you are going through, I went ahead and bought a new IACV and its still doing the same.

 

have you not taken it to shop yet? what did they say?