Help Needed 89 Ls Integra

[RibSmasherAu]

Hi all just wondering if anyone can help, my integra keeps reving to 3000 then drops to 900 and revs straight back up again and drops does this over and over again when you first start of a morning and even after been running for 20 mins or so sometimes, any ideas?

[A-man]

idle control valve? clean it out maybe?

[EuroAccord13]

Sounds like the engine is rev hunting... Could be a vacumn leak, if that is not the case, you might want to look into the idle solenoid located on the TB.

[deanthom]

Ah, the infamous hunting idle! I've had this problem too. It's caused by more air getting into the intake at idle than the computer expects. What happens is, there is an air leak somewhere, either through a vacuum leak or one of the idle control valves playing up and the ECU MAP sensor sees more air coming in, so it increases the amount of fuel into the engine to get the correct air/fuel ratio. This of course causes the RPMs to increase. It does this until the RPMs get too high for the "idle" mode and the ECU cuts the fuel, then the cycle repeats. At least, that is my understanding.

Anyway, if your problem isn’t a simple vacuum leak, then its probable either the fast idle thermo valve (FITV) or the idle air control valve (IACV). The FITV is a simple thing that just allows a bit more air in when the engine is cold and as it warms up a wax pellet melts and closes off the intake. The IACV is controlled by the ECU. I'd check the FITV first, you can actually adjust how much air it lets through by pulling off the back and tightening up the white plastic ring inside, this will reduce the airflow. This isn't really meant to be adjusted but sometimes it will unscrew itself loose over the years. It takes a bit of trial and error to get it back to the right spot. G2IC.com has a fair bit of info about this:

Bad idle troubleshooting:
http://www.g2ic.com/forums/showthread.php?t=42969&highlight=idle+troubleshooting

FITV info and adjusting:
http://www.g2ic.com/forums/showthread.php?s=&threadid=44386

IACV cleaning:
http://www.g2ic.com/forums/showthread.php?t=35534&highlight=iacv

Hope that helps!

Dean

[Rehaan Khan]

maybe its ur spark plugs mate...does it sounds like a wrx once u drive???