Car won't idle in cold properly

[chisox7858]

So my car will not idle high enough and stay at a consistent rpm while cold. it falls like it wants to die until its warm. once warm its fine.i replaced the idle speed control motor, checked for a boost leak, and i cant figure it out. Any suggestions?

 

[spoonman]

If the ISC motor is good and you have no boost leaks it is probably your FIAV which raises the idle for cold starts.

 

[AlaskanDsm]

Are you talking about the idle surging? Like goes from lets say 700rpm to like 2000rpm over and over until it warms up?

 

[chisox7858]

It will start at about 900 for 4 or 5 seconds, then just drop to like 3-400 and back and forth. it will not surge to anything rediculous like 2k or up.

 

[spoonman]

After a few minutes of idling does it have a good solid idle at 750ish?

 

[chisox7858]

Well it will warm up about 25% and start to idle fine. its just the initial startup that is giving me issues.

 

[-LA-]

If the ISC motor is good and you have no boost leaks it is probably your FIAV which raises the idle for cold starts.

Can you please tell me what you are calling a FIAV ? Excuse me ignorance.

 

[blownturbotsi]

FIAV is something to the extent of Fast Idle Air Valve, I believe. It's what raises the idle when the car is cold until it warms up, then will go to the normal idle.

 

[-LA-]

Well it will warm up about 25% and start to idle fine. its just the initial startup that is giving me issues.

There is more than just one thing that can cause that.

ECT-(Engine Coolant Temp.Sensor)- When the sensor is faulty, the engine coolant temperature is regarded as being 176 degrees.

Driveability may become poor and the idle quality will suffer during cold operating conditions. The trouble may not be noticed when the engine is warm.

IAT-(Intake Air Temp. Sensor)- is a resistor which measures the intake temperature, and feeds it to the ECU, then the ECU will determine the intake air temperature according to the output voltage from the sensor, and compensates fuel injection amount according to the IAT.

When this sensor is faulty, the idle can suffer, when temperature is below 77 degrees

Maybe look into these also, since you have replaced IAC motor

 

[turbo90gsx]

Check and make sure your throtle plate is closing all the way and closing the idle switch completely. It may very well be a faulty ETC but OBD should pick that up at some point and toss on your check engine light. It won't be a IAT sensor because you don't have one. They are only used for speed density calculations and our cars(4g63's) utilize MAF/MAS sensors, and a MAP for you 2g guys.

-LA-, you have a 420a not a 4g63, each use different ways managing fuel calculations for idleing and driving.

 

[-LA-]

Check and make sure your throtle plate is closing all the way and closing the idle switch completely. It may very well be a faulty ETC but OBD should pick that up at some point and toss on your check engine light. It won't be a IAT sensor because you don't have one. They are only used for speed density calculations and our cars(4g63's) utilize MAF/MAS sensors, and a MAP for you 2g guys.

-LA-, you have a 420a not a 4g63, each use different ways managing fuel calculations for idleing and driving.

For sure. I looked and thought his car said 98 RS. Guess i need some glasses. Sorry about that mate