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Erratic Idle... Especialy when cold

Posted: Wed Mar 01, 2006 3:06 am
by OzyEJ22
Just want to start of by thanking you guys, this site is fantastic.

Well when i first bought my '92 liberty FWD ej22, about 2 months ago i got rid of the that stupid intake silencer thingy and the original pannel filter.
Sounds great. not sure if i got any performance from it but it certainly sounds like it goes harder :wink:
Everything was running perfect as far as i can tell....

About two weeks ago i modifyed the exhaust, I was going to to clear out the center cat but it was already straight through.
replaced the rear muffler section with a straight through 2.5" section. :twisted:

Sounds F*&$ING SPECTACULAR, and it definitly helped with top end power. :D

Before last weekend i had only driven the vehicle twice maybe three times since installing the exhaust. everything ran beutifully.

Last weekend I took the liberty for a run to hobart (about 4 hours drive each way). Did not drive the car particularly hard. As i was aproaching a round about on the drive back I realised that it was idling at about 1500rpm. I have never noticed this before, but just assumed it had somthing to do with the long drive.

but alas that was not the case, when i start the car it revs at about 1500. if driving down the road at say 15mph and the clutch is released it idles at about 2000. when the clutch is released as the vehical is coming to a stop the revs rise to about 1500 the gradualy die down to where it should be (750rpm) this takes about 5 to 10 seconds..........

Any ideas...... i'm stumped.. oh BTW it isnt throwing any error codes

Just one more thing, does it seem odd to anyone else that i have ALOT more LOW end power when the car is cold..... any other car i have had has lacked low end power when cold and reved out better than usual.. (more compression i suppose)

Posted: Wed Mar 01, 2006 4:48 am
by OzyEJ22
There is one more symptom that started at the same time as the erratic idle that i should have mentioned before.

When cold the engine has a hell of alot more power than it ever has from 1000 - 4000 rpm

But when the engine is at operating temp it will missfire when trying to accelerate from 1000 - 2000 rpm. this has never been a problem in the past

Posted: Thu Mar 02, 2006 1:02 am
by stipro
The high idle sounds like a coolant temperature sensor gone bad.

Posted: Thu Mar 02, 2006 10:51 am
by OzyEJ22
Cheers, I'll check it out tomorrow.

Do you know what voltage's it should be putting out when hot/cold?

Posted: Fri Mar 03, 2006 12:56 am
by stipro
VRG3 wrote:The manuals for US models say that you should measure 0.7 to 1.0 volts on the hot side of the sensor (and 0 on the ground side) when the engine is fully warm.
This was the info that I found. I hope it helps :D

Posted: Fri Mar 03, 2006 2:17 am
by OzyEJ22
thanks again.

just reset the ecu this morning (had not been done since i "fixed" exhaust), seems to have nearly fixed the problem :roll:

Posted: Fri Mar 03, 2006 4:07 am
by OzyEJ22
BTW. I've just had a look through the 1992 USDM subaru workshop manual and to check the water temp sensor it says
Measure resistance between water temp. sensor terminals.
Specified resistance:
2.0-3.0k ohms (20'C (68'F))
0.3-0.4k ohms (80'C (176"F))