RPM goes up and down
 

Here is the problem i m having. civic MT, 2003, 42000 miles. I had my oil change (myself) about 400 miles ago. Now I starrted expericing this problem. 1: when i start my car it starts at around 1500 RPM, it was starting around 1250 RPM, ( i know you would say wearther effects, but trust me, its same) this is when i noticed something strange. Now after driving around, when its in netural, it stays around 1000 rpm and drops to around 750 rpm after 20-30 seconds(this wasnt the case, it was dropping to 750 rpm). and now when the engine fan kicks in, rpm goes a little bit high, around 1250 rpm, also when i turn the steering around. rpm goes high. Any idea whats causing this ? please advise.

Thanks

it sounds about normal to me.

for the steering, it is all run on belts so the rev will go up a bit.

but what about when its in netural and stays to 1000 RPM ? this was never happening. it was always coming down to normal which is 750 RPM.

when was the last time the airfilter was changed or cleaned if you have a K and N.

i would say around 12000 miles ago. shouuld i check ?

wouldn't hurt, the engine could be straining to pull in more air

worst case reset the ecu; disconnect the batter for a few minutes. This will make the computer adjust itself.

Now is the car running any different then before?

Most everything you described is normal. When you first start the car, the engine is cold so RPM's will start off a bit high. Once it warms up, the RPM's come down. Now anytime the engine has a load on it, the rpm's will increase a bit, but usually the IAC (Idle air control valve) will kick in and even out the idle (RPM's). Same with the steering, when you turn the wheel left or right, you are building pressure in the system which is basically adding a load on the engine. Now there is a Power steering pressure switch on the steering rack (Rack and Pinion) that sends a signal to the computer to bump up the idle when it senses a load change.

I agree with both of your response. But one thing is it doesnt seem normal to me. but let me try resetting the ECU. and see what happens. could it be little more oil when i changed the oil ? i know i added 3.7qt oil with the filter. but let me try resetting the ECU. thanks and let me do this first.

i did reset the ECU and took the K&N filter to check and filter was good. after putting negative cable back in and running car for 10 min. everything looks fine. lets see what happens next. what could have caused it ? any idea ?

Sounds like the idle curve got screwed up some how. It's happened to a few people on here before. Go to the link, gearbox talks about how to do an idle relearn if the problem surfaces agian, this should take care of it.
http://www.7thgencivic.com/forums/sh...d.php?t=221592

yeah i did reset the ECU by taking off the negative cable and letting car run for 10 min, but havent drove the car yet. lets see if this has resolved it. if not then i will do it agian. thanks a lot

^ I've got the same problem, however the rpm's go up to 1500 after warmed up, I've already done this re-learn and still the same problem?????

When it warmed up? what about when the car is cold, how long does it take to get to this point?

I've had this same problem for the longest time ... resetting it didn't help me ... it just idles at 1k rpms until I come to a complete stop ... but it'll drop to 750 after 2-3 seconds ...