Car runs rough, no CEL

[max]

This is 2005 Subaru Legacy GT 2.5L turbo engine.
So my mother starter her car in the morning and it was shaking like it has bad vacuum leak, there’s no CEL. I know she filled up a couple days ago, maybe bad gas?
What could be causing this, where could I start checking?

Topic

[Joeseph Mama]

use some starter fluid and check for vacuum leaks.

also check for a clogged catalytic converter.

[max]

I would think I’d get CEL with vacuum leak?

[Lorrin Barth]

Found out the other day my wife’s ’04 WRX has had a vacuum leak for the last 37,000 miles. No CEL.

[max]

So car gave me P0302 code, misfire on cylinder #2.
I;ve pulled coil off and took out spark plug and they looked good. I inserted spark plug into coil and tested for spark and there’s strong spark coming from spark plug.
There was also sparking coming from red circled area (in the picture) is that supposed to ground to the engine? It’s metal plate (magnetic core) and there was spark coming from it to engine if I held it closely.

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[Lorrin Barth]

Well, I’ve never seen a coil do that. So, I’m going to venture that it is bad, secondary grounded out to magnetic core.

[max]

I’ll try swapping coil to another cylinder and see if CEL changes to that cylinder. It’s just a pita to change these on this 05 Subaru GT, they are made for midget hands.

[max]

Weird thing but I’ve swapped coils between cylinder 1 and 2 and reset CEL and then I turned on engine to see if CEL would come back. Car idled rough for 1/2 a minute or so and then started running great again!
I went to gas station and topped off tank (2.3 gallons) and its been running great on way back from gas station.

[Lorrin Barth]

I’d suggest you swap cars with your mother for a day or so. If the problem doesn’t come back I’d call it a fix.

[EricTheCarGuy]

It could be a fuel issue. With performance diagnosis, it’s a process of elimination. This article outlines the basic steps.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

Keep us posted on how things turn out.

[Author]

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