2007 Subaru Legacy Turbo GT Check engine light comes on when car idles rough. This rough idle only occurs for a copule of stop lights then it smooths out. The light eventually goes out after a couple of drives. Eng. light only stays on steady and there is no hesitation or roughness whenyou take off. I believe the car originated in CA but I live in KY and use 93 octane only.

something that wont throw a fault code
i am thinking coil and plugs
even fuel pump relay or bad fuel

engine bay picture removed
2005 subaru legacy

is yours the turbo motor .. could be turbo related

Depends on what you mean by rough. Could be a cylinder misfire.They sometimes are not noticed as engine speed increases during driving or under light load as when idling in neutral but at idle under load as when stopped at a light in drive became noticable.
Could also be running rich. The causes of either are too numurous to list.Consult a good mechanic who can actually see and hear the problem to put you on the right track.

try the crank speed/position sensor as this controls the engine revs as well as other things

i would check the idle air control solenoid first. simply unplug it then remove the unit and inspect the air passage for any blockage and carbon buildup. Clean it if its dirty then test it out. If the IAC is good then you should look at the throttle position sensor.

Hi shoemaker.
Fuel filter issues show up in high demand fuel needs such as passing or going up hills. Rarely do they cause rough idle problems.
Is the check engine light on or flashing? A flashing light indicates engine misfire and should be repaired as soon as possible.
So you could have a vacuum leak, a stuck EGR valve, bad ignition coil, worn spark plug, and many other items.
If you don't have a check engine light and haven't done a tune up do one to eliminate a few items and see if that smooths it out.
If you have further questions ask me and I will check and answer you.

KL

I have the same problem!Running on three.I have checked compression,wires,plugs.Changed injecters,plugs.
3 mech.cant figuire it out???

if you didnt have the issue with the check eng before then I would take it back for them to reinspect the job. And at least have then put a scanner on it to check why the light is coming on at idle.

I'd suspect a vacuum leak in the inlet manifold, check to see if any vacuum lines might have fallen off. This can cause a lean misfire at idle, but often it's not enough of a leak to make it lean enough to misfire at higher rpm. If a leak is not obvious, check if it is a leak by buying a can of engine start (or even CRC will do) and spray it all around the inlet manifold. If the idle smooths out while you're spraying then then goes rough again, it is a leak. By spraying in specific areas you can narrow down the area of the manifold or gasket that is leaking.

Hope this helps.

I have the same exact problem, but with idling roughly between 700 and sometimes upwards of 2000+ RPM.  I don't have the problem you do as far as the engine heat goes, but I definitely feel the tug, hear the engine sounding bogged down at stops, and when in neutral, finding it idling extremely high.  My check engine light had come on just this past month (with this problem occuring for a little over a year now), and it turns out I have a bad Throttle Positioning Sensor, which my mechanic says can cause the high idling.  I'm replacing the sensor this weekend with a dealer part, which I got for $102, so I'll post again once it's done to let you know if that fixed the problem or not.
Hope this helps,
Dan e-mail: [email protected]