Low idle when cold

[triggerman]

Hello,

My '94 1.6L 3spd auto with about 375,000km's has developed a cold idle problem. After sitting for a little bit (10 hours or so) it will idle really low. This problem gets worse the colder is gets. It seems like if it gets a little colder (-15°C) it will stall, since it's almost stalling now (-3°C).

When I first start it it will idle at about 750rpm when it's cold, and after about 5 minutes of warm up it will start to increase to about 1200rpms. I can press the accelerator pedal and it will run fine without a problem. I changed the plugs, and wires this summer, and changed the cap and rotor around this time last year.

Any thoughts on what might cause this? IAC comes to mind.

[96coroll]

the thermostat? may be defective thinking the car is already warm

[speedy25]

IAC is almost ALWAYS the cause of ALL idle problems.

-SP

[Bitter]

except mine...still idled low after IAC, thermostat. some have had success with the engine coolant temp sensor. you may need to adjust the throttle position sensor as well due to minute wear in the throttle mechanism and throttle stop.

[sequoiasoon]

Mine was caused by a faulty temp sensor. There are 2 sensors by the Tstat housing. One controls the fans the other tells the CPU what to set mixture at based on temp. Mine was failing the exact same way. It would barely run and got worse the colder it got. After a couple minutes it worked perfectly. I took mine out and tested it per instructions in the service manual. It involved putting the sensor in the feezer and reading resistance. The new one was like $20 iirc.

[triggerman]

Okay. I've cleaned the IAC with some throttle body cleaner and have noticed an improvement in idle, but the cold idle problem still exists. I'm having some difficulty identifying the water temperature sensor as there are two (I think) "things" the thread into the thermostat housing. One has one wire which I'm guessing is the water temperature sender and one has two wires which is the sensor? Is there a picture or a diagram that I could refer to?

[sequoiasoon]

Originally Posted by triggerman

Okay. I've cleaned the IAC with some throttle body cleaner and have noticed an improvement in idle, but the cold idle problem still exists. I'm having some difficulty identifying the water temperature sensor as there are two (I think) "things" the thread into the thermostat housing. One has one wire which I'm guessing is the water temperature sender and one has two wires which is the sensor? Is there a picture or a diagram that I could refer to?

The 2 wire one is the one you want to change. Dealer probably has picture for you. Somebody with a service manual might be able to help out. I sold mine sorry, but iirc it was the one on the bottom of the t-stat housing. I can check colors tomorrow in daylight but from the web

"The coolant temp sensor is a two wire sensor located to the [COLOR=green ! important][COLOR=green ! important]drivers [COLOR=green ! important]side[/COLOR][/COLOR] of the cylinder head. The sensor is screwed into a coolant pipe. The two wire colors are white and brown"


[/COLOR]