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2012 XT Touring 4EAT
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Discussion Starter · #1 ·
My 2012 FXT has been throwing fits in the past few weeks. The vehicle runs fine on the highway or around town. Gas mileage is good actually seems to be improving. But, if the car is stopped when hot, allowed to sit a few minutes and then re-started, it coughs and sputters and acts like the world is ending. It also throws P030n codes (this morning's edition was P0301 and P0303, but it's also misfired on one cylinder and on all four cylinders. If the vehicle sits for an hour or so, it starts and runs just fine.

I've been checking likely causes, but so far have not found the problem:

- I cleaned the MAF - but not really that dirty.

- I've got new NGK LFR6AIX spark plugs to install, but the NGK [email protected]" plugs in the engine only have ~25k on them.

- I removed and cleaned the purge valve, but it seemed alright - nothing obviously wrong Are there other valves that could upset the fuel system?

- I've been looking for vacuum leaks, but so far have not found anything major or likely to cause a problem.

The engine acts like some system or valve is no re-setting properly, or maybe it's failing - on it's last leg - so hot re-starts are a disaster area. Once the engine starts and runs a bit, then the only reminder is . . . the P030n CEL codes (steady, not flashing).

Suggestions? Thanks

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Since it is on all four holes, frequently but random, I'm wondering whether this couldn't be a bad coil pack. I've seen them fail like that on a different make car.
If you can get your hand on compressed air or freeze spray, first make the condition happen. Then hose the coil pack down with compressed air or freeze spray. If the problem goes away, that coil pack is suspect.

I wouldn't just start swapping suspect parts but this would give you a starting place.
 

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Discussion Starter · #3 ·
Since it is on all four holes, frequently but random, I'm wondering whether this couldn't be a bad coil pack.
Turbo Foresters have coil-on-plug ignition. When only 1 hole showed up as a misfire, I,too, thought I might have a bad coil-on-plug but not all 4 at once, and not random assortments. When I get around to changing the plugs (probably this weekend), I might swap out some coil-on-plug packs, but at the moment I don't see a clear plan on what this might accomplish.

One more thought: the strain on a coil-pack or coil-on-plug should be greater at highway speed. The car runs fine at highway speed. It runs fine around town. What it does NOT do is run well right after a hot start.
 

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Discussion Starter · #5 ·
Ok, yeah in that case it likely isn't any of the coils.
Did this problem just occur one day and stay?
I noticed it several weeks back (P0301 CEL) but didn't think that much about it - just noted the code (P0301), cleared it, decided it was a fluke (hey, Subarus throw CEL codes). Since then, it's gotten worse - much worse - and now shows up on different or multiple cylinders.

About10 minutes ago, I started the car (cold) drove down to the corner UDF and filled up the gas tank. It started and ran flawlessly - both going and coming back (about 1 mile each way).

I'm picky about where I buy gas - mostly 93-octane at Mobil-serviced stations. It's possible I got a bad batch of gas. So, I just added a can of Seafoam to the tank. It will be through the engine by tomorrow evening - highway miles. Stay tuned on that.

Still on gas, I keep fairly meticulous records on fuel usage - a good predictor of engine health. I just ran the numbers and the car (last 3000 miles) is performing a bit better than it's lifetime average - and turned in the second-best '3000-mile block' ever (22.60 vs 22.73 mpg). If the mileage had fallen off, or if it ran poorly on all starts, but nothing so simple.

It only seems to occur on hot starts. For example: early this morning, I drove from Dayton to Chlli (~95 miles). The car ran great until I made a quick pit-stop along the way (~55 miles out). Criminy, when I restarted, I thought I would have to call a tow truck ;-(. CEL was solid for the rest of the trip. Got to my destination, did my duty (3 hours).

Before departing, I cleared the CEL codes (P0301, P0303 - every Subaru owner carries an OBD-II scanner in the glove box, right?). It ran flawlessly back to Dayton (with no pit-stops). Parked at a meter downtown, ran in a building on a quick errand (15 minutes), came out . . . and I thought I would need that tow truck again. It actually did not throw a CEL code but it wanted to (the CEL light came on briefly, then went out). Then, it straightened up and ran okay to home.

Demonic possession?
 
2017 2.5i Fozy CVT
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And If it is going bad, the ALT is working overtime trying to keep up.
ALT test wouldn't hurt either.

Does it start easy/turn over like it always has?

In this hypothetical, the coils are getting worked up on a long drive as they are supplied with insufficient V.

Or maybe the V supply to the coils is somehow disrupted. See if you can dig up a schematic of the ignition.
 

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Discussion Starter · #11 ·
And it would be acting as a big (hot) resistor to the ALT trying to charge it for an extended time. ALT test wouldn't hurt either.

Does it start easy/turn over like it always has?
Yes, it does start and turn over like before.

I just got back from the battery shop. They load tested the battery for almost 4 minutes - it held up fine. It's 4 years old, FWIW (the battery guy found some code on the battery).

He also tested the alternator - it was fine. No surprise there, since the battery was fully charged.

After this 10-minute visit to the battery shop (with the hood up), the car did start but it bucked fussed a bit. At least no CEL.

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Since this problem only seems to show up on 'hot starts' after only a few minutes sitting, it's possible that the problem has existed for some period of time and I just didn't notice it. That is, I don't necessarily use the car through that cycle (engine fully warm, engiine stop, re-start after a few minutes) all so often.
 

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Discussion Starter · #14 ·
Plugs are my project this weekend. All parts on hand. Yes, iridium plugs are in there now and the new plugs are iridiums. If the old plugs have any off-coloration or other tell-tale signs, I'll post a picture.

I also got a new Denso front O2 sensor (probably installl this weekend). There is no regular change interval for this part. OTOH, it is so critical to running the car, and it lives is such a bad neighborhood, that I would probably change it even without some major problem. So, stay tuned.
 

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Discussion Starter · #15 ·
Good news: Okay, new plugs were installed. It's a PITA to do plugs on a turbo Forester, but the installation was uneventful. The new plugs were gapped to 0.028". The old plugs looked okay - nothing remarkable except that the gaps were huge - close to 0.040" or more. It's not clear how that happened. I installed them ~25k miles ago and specifically re-gapped them to 0.032".

I did not get the front O2 sensor installed - maybe Monday. The old one was in there so tight that my O2 sensor tool started rounding corners. I'll put a torch to the old one on Monday - that'll get it loose.

Starting last week, I ran 2 cans of Sea Foam through 2 tanks of gas. I also puirchased my gasoline at a different retailer.

Bad news: All of the above does NOT appear to have solved the problem(s). That is, the vehicle still starts from cold and runs perfectly. But starting from hot is dicey. When it does start and gets past the sputtering and mis-firing, then it runs okay (but the dash may be redecorated with yellow lights ;-(

I'm running out of ideas.
 

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2018 Forester 2.5i Base CVT
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I would check the following:
  • coolant temperature sensor (use OBD tool to read temps, or your MFD if it has this capability)
  • crankshaft position sensor
  • camshaft position sensor
  • leaking injector / fuel pressure regulator (check for fuel line pressure drop characteristic)
  • check for intake leaks past MAF
  • recheck again and closely for vacuum leaks
  • I do not know how to check AVCS solenoids, but they can screw up your ignition timing as well
I do not think the problem is an ignition coil related as it occurs only on warm restart. Degraded ignition coil would manifest itself at anytime when hot.
On any of the above sensors check for scuffed or broken insulation, clean sensor connector terminals.
Good luck, keep posting updates.
 

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2018 X3 M40i / 2016 X3 xDrive35i
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Leaking injectors. Had the same problem after I had them cleaned...not sure why but the cleaning caused one to leak and 10 to 15 minutes after shut down hot start was stumbling. Left several hours the fuel either evaporated or washed down cylinder and it would start fine cold.

Replaced all 4 injectors with Denso aftermarket and they are performing well.
 

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Discussion Starter · #19 · (Edited)
Okay, here's the latest chapter. I started the car this morning (cold) - it ran flawlessly on a 70 mile trip. After a 3 hour wait, it started and ran fine on a trip back. I even blew off an Audi on the trip home. But when made a local stop - in and out in 15 minutes - major stumbles, CEL (P030n all 4 cylinders), etc.

At this point, I don't see why my injectors would suddenly start leaking (they have not been serviced or cleaned). Possible, of course, but not likely. I think the problem is in one of two areas (and they overlap): 1) there could be a vacuum leak that I simply haven't found (and not for want of looking). The leak is small enough that when the vehicle gets up to speed, the leak is still causing mischief but it is not as significant.

Or, 2) there could be a failing component, such as the purge solenoid valve, which is sticking open - either all the time or at least until the vehicle cools off, after stopping.

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In an earlier message I said I checked the purge solenoid. Not so. It turns out I was checking something else, instead. I determined this by unplugging a particular component, then reading the CEL codes (which identified whatever component did not register as a completed circuit). Honestly, I can't even find the #@#$% cannister purge solenoid. I know it's there somewhere, but it is well hidden. The purge solenoid may or may not be working correctly. Ditto for some other component which might open (or vent) when the engine is running at power but fail to close promptly when the engine shuts down. My bet is that it is either that kind of component failure - or else a full time vacuum leak.
 
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