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'91 Sub non-turbo, auto, Legacy with idle issues

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First of all...Hello and what a great forum!

Now, the issue at hand. The car has 125K miles on it. Cold start is just fine. But when I have to stop at a traffic light or a stop sign after having driven a mile or so subsequent to a cold start, the engine wants to stall. It goes through what is best described as a "shudder" a couple of times threatening to stall. Then the idle is stable for the rest of the drive. The other problem with engine idle happens when starting the engine after it is been running for a while...like when stopping briefly to pop into a store. Then, the engine idle cycles between near zero and about 1,500 rpms several times before stabilizing. After that, the engine runs fine and idle is fine. I have read, in these forums, that the coolant temperature sensor or the idle air control valve (or both) might be good candidate culprits. Cost-wise though, the IAC is well over $300 (OEM) while the coolant sensor is about $30. They want 0.5 hr labor for each. Not being technically inclined myself, I'd have to use the shop. So, my questions are:

 

1. What, in the forum's opinion, might be the problem?

2. How would you proceed with the fix?

 

Thank you for all your help.

Shouldn't be having those problems at just 1.25k! (I'm guessing you meant 125k.)

 

Have you checked for codes? That's the best place to start, otherwise you're just throwing parts--and money--around and hoping.

 

That said, the engine temperature coolant sensor might be worth a try.

 

Take your IACV off and give it a thorough cleaning before spending big bucks on a new one. Search the forum--it's been talked about a lot.

 

Good luck!

  • Author
Shouldn't be having those problems at just 1.25k! (I'm guessing you meant 125k.)

 

Yes <sheepish grin>

 

Have you checked for codes? That's the best place to start, otherwise you're just throwing parts--and money--around and hoping.

 

No CEL, really. And whatever codes might have come up were cleared when the O2 sensor was replaced.

 

That said, the engine temperature coolant sensor might be worth a try.

 

I am leaning towards that...least expensive.

 

Take your IACV off and give it a thorough cleaning before spending big bucks on a new one. Search the forum--it's been talked about a lot.

 

I'd be at the mercy of the shop for that...dunno how much labor they'd charge for that.

 

Good luck!

 

Thanks....much appreciated.

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