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1990 legacy - cold idliling ends in RPM spike then stall

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As the title suggests, when the motor is cold, the idling will slow down almost to the point of a stall then jump up to 1200 and then fall and often die. I generally just hold my food on the gas for a couple of minutes and then it will idle but low (around 500). As it starts to warm up the idle slowly works its way up to just under 1000. Also, when it's cold, If I turn on the lights, stereo or anything else, I see a small dip in the idle speed.

 

No check engine lights.

 

Kinda confusing for me.

Hm...is your IACV intake hose firmly 'plugged into' the intake? If not it allows air to bypass the MAF and it will act all kinds of weird for idling. This hose often pops off when the air filter is replaced.

The IAC could need to be cleaned. Pretty simple, just remove the hose and spray some cleaner into it with the engine running. Throttle body cleaner works great for this.

  • 7 months later...
  • Author

After replacing the clutch cable, I mildly cleaned the IAC and now when it starts it idles high! About 1 and a half. When it warms up it levels out. Is that still the IAC you think? After inspecting the hoses, I have found a small crack in the hose going into the IAC.

1500 RPM is about right for a cold start idle. It should slow to about 750 rpm over the course of about 30 seconds to several minutes depending on outside temp.

1500 RPM is about right for a cold start idle. It should slow to about 750 rpm over the course of about 30 seconds to several minutes depending on outside temp.

 

+1 - this is normal cold start behavior. the colder it is outside, the longer it will stay at high idle.

  • Author

I've noticed though, that it will level out (it wont go under 1100) in a minute or so but if I drive off and stop at a stop light, it will still be high when warm (sometimes up to 1700). When it is fully warm ten minutes later or so is when it will truly level out.

 

I guess I'd rather have it high than low for the cold season coming up... Still have those nasty snow tires. :headbang:

 

There is a crack in the IAC hose... Just going to replace that.

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