hey all,
for some reason today, while warming up my MY94 WRX, it was doing some funny idling. the revs would go all the way down to almost 700rpm (and sound as if it was gonna stall) and then suddenly go all the way up to 2000rpm. it did this about 5 times before the idle stabilised at 1200rpm.
anyone had this problem before or know what it could be caused by??

Lambda sensor, MAF sensor, coolant temperature sensor for starters. Check it on a Select Monitor.

Yep,

Quite a few of us pre My97 peeps trying to solve this one.

All of these could cause erratic idle

ECU Power & Earth (common problem on earlier models)
MAF
Engine Coolant Sensor
Throttle Position Sensor
Fuel Pump
Pressure Regulator
Fuel Injectors
Coil Packs
Spark Plugs
Camshaft position sensor
Idle control valve
Lambda Sensor
Wastegate control solenoid

In my case the idle is erratic when cold/warming but car drives/performs normally etc & idle is ok once driven a bit & fully up to temp.

If these are the symptons you are seeing then I think you may be able shorten the list to the following :

Idle control valve - (In my case this seems ok)
Idle Switch
Engine Coolant Sensor
Throttle Position Sensor - (I think Scott.T may have eliminated this one from his?)

For what its worth - For my problem - I think my money is currently on the Engine Coolant Sensor.

Hopefully Scott.T will post as he's investigating it all too.

Let us know how you get on.

Cheers,

Chris

[Edited to correct some spulling mestakes]

[Edited by Chris.Palmer - 5/23/2002 10:53:46 AM]

cool. thankx for the info chris.
it hasn't done it since then so itz a little weird, but if it happens again, i'll see what i can find out.

Hopefully its just a duff batch of petrol then.

Having said that mine did start as a one off & got gradually worse over winter then got better as the weather got warmer & now does it on & off but not every day.

Never seen warning light or anything so Dealership & Select Monitors are a waste of time & Money.

Best of luck & I hope yours is just a one off.

Cheers m8.