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EA82- Rough Idle -Runs better without IAC connected? Why?


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Hey all, 

 

I have an EA82 that I've been trying to get back on the road for about 3 years now.  I love this subie so much, but can't seem to diagnose what the heck is going on.  

 

The primary issue is low idle, and inconsistent running.  It bucks, and jolts, stalls, and is basically underivable.  Based on stuff I've tried on the forum, I've replaced a lot (list below).   However, I have noticed 2 things over the weekend.  The issue is much worse when the car is started from cold.   If it warms up (which is tough to suffer because it runs so poorly) the idle seems to stablilize a little bit.  

 

Also, today, when messing around I unhooked the Idle Air Control Valve, and it seems to run much much smoother.  Not 100% perfectly, but a heck of a lot better.  It's actually driveable.  Does this just mean that my IAC is bad?   I sort of doubt that as it's only 2 years old and was new when I got it.   (I've got the idle turned up pretty high too)

 

This is the biggest result I've been able to find with all my testing and new parts (used MAF Sensor, new Oxy Sensor, new EGR, new coolant temp sense, used throttle position sensor, new plugs/ wires, new timing belts, etc).  

 

Any ideas on why it would run better without the IAC connected?  I feel like I might be getting close here...hopefully?  

 

Thanks all, 
Jason

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SPFI? If its been out of service for three years condition of the fuel, gummed up injectors, and corroded grounds need inspected. Is this issue what has been keeping the car from being driven? If the car is SPFI what are you doing to raise the idle?

 

If you dont already have this heres a link to an fsm. You need this! http://jdfinley.com/downloads/SubaruEA82-ServiceManualPart2.pdf

 

As stated above check the condition of the grounds (especially the one by the tstat housing). do you have a digital ohm meter?

Vacuum or Intake manifold leaks you should inspect the boot clamps and hose to the IAC valve as well.

Fuel pressure, do you have access to a gauge? With your symptoms this is must check.

Pull the cap on the disty and take a look inside, see if its corroded and gross (not just the cap and rotor). While there. check for play in the rotor and shaft.

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