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2008 Subaru Outback 2.5i
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Discussion Starter #1
Hi all, my outback recently hit 120,000 miles and started to shudder/hesitate at lower RPMs. It only happens when I punch the gas, but if I roll on it real easy it doesn't happen. Last week I stepped on it really hard and it lurched like anything and the check engine light came on (not blinking), and later I find a P0303 at AutoZone.

I used B.G 44k cleaner in the fuel tank, drove it a couple hundred miles (feathered the gas pedal) and it drove almost normally, the hesitating went away by a lot. I cleared the code and have been driving it since and it's been driving normally, and the code has not returned. However, if I step on the gas harder than a granny would, it still hesitates a bit, but not as much as before. I'm planning on getting the spark plugs, wires, and coil, changed but haven't had a chance as I will be traveling extensively the rest of the month.

There is no overheating, it's not burning oil, no loss of power (except for some slipping and lurching at low RPMs). In short it's great. I'm going to have it diagnosed at the local mechanic's, but was wondering if there are any simple checks I can do on my own that may shed light on this issue? I have a shallow familiarity with cars but am not a very hands on person.

I'm really hoping it's not a loss of compression because from my research that's a death sentence to the engine and I've spent so much money already fixing her up. Sigh. I'm actually super scared of this happening so am starting this thread preemptively for insight. I'm scheduled for the 19th to have it checked out. Thanks.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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when was the last plug change.?

the regular plugs only have a 30,000 mile interval.

NGK plugs and wires are what subaru likes,...NGK double platinum plugs last longer and are only about $18 for this car as they are so small.

you might have some oil on a plug at that many miles, as the car needs plug O rings (and typically valve covers)

_____

what not to let anyone talk you into getting: a aftermarket coil , I would put a used "subaru" coil on before a new aftermarket one.
(my old 2002 H4 one says "subaru" etched on the front.).
 
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2008 Subaru Outback 2.5i
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Discussion Starter #3
when was the last plug change? the regular plugs only have a 30,000 mile interval.
I'm not sure to be honest, I got the car at 99k and haven't replaced the plugs since. I will definitely do those things you recommended, but have a question first:

What are the symptoms of a loss of compression? Does it stand out any differently from just mere spark plug deterioration? I'm reading stuff about burnt valves and head gaskets and the intensity of it has my head spinning. I can't afford to replace / rebuild my engine at this point. Maybe some reassurance would help lol.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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I'm not sure to be honest, I got the car at 99k and haven't replaced the plugs since. I will definitely do those things you recommended, but have a question first:

What are the symptoms of a loss of compression? Does it stand out any differently from just mere spark plug deterioration? I'm reading stuff about burnt valves and head gaskets and the intensity of it has my head spinning. I can't afford to replace / rebuild my engine at this point. Maybe some reassurance would help lol.
easy thing is to look at the plugs and see if you got oil on that plug. or its just plain old and the first to fail.

plugs are $18, wires are about $45, quick for a shop to install them on this. (buy them on rock auto, or amazon).

plug orings and valve covers are just a bunch of rubber gaskets and not that expensive to buy either. (a little time consuming but shops do it all the time,..with a little bit of RTV goop in prescribed places).

all subarus plain H4s 2000-2009 will need head gaskets at some point, they typically leak oil externally,...check your oil, keep it filled, put up with some stink when you stop at a stop light, and save up for the job. ($1500-2000)

timing belt ? did you replace that yet? ticking time bomb if never done ....danger danger at the miles you got now.
I would buy a Aisin branded kit. (all japanese components, execpt the US made belt, and none of it chinese junk like ther rest of the aftermarket companies).
 

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2008 Subaru Outback 2.5i
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Discussion Starter #5
all subarus plain H4s 2000-2009 will need head gaskets at some point, they typically leak oil externally,...check your oil, keep it filled, put up with some stink when you stop at a stop light, and save up for the job. ($1500-2000)

timing belt ? did you replace that yet? ticking time bomb if never done ....danger danger at the miles you got now.
Yup timing belt and head gasket were both taken care of at 98k miles. I bought the car at 99k. Guess the original owner had enough of it. I'm also having second thoughts after how much has gone into repairs. Anyhoo, the oil is fine and is not leaking, nor burning, which is nice.

My impression is that if not plain spark plugs and wires, it could be something injection related since the BG 44k cleaner helped a lot and noticably reduced the shuddering action at low RPMs.
 

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'14 Subi OBW, '18 Subi Forester
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I wouldn't jump to thoughts about compression issues or the like if the engine idles reasonably well and runs well under most conditions.

You logged a P0303 misfire code, so at least you have a place to start - a cylinder that's having the most difficulty. As Eagleeye already said, start with the basics. Plugs, wires & coilpack. (Just for my knowledge and because I'm feeling too lazy to go look it up, when did they switch to individual coil-on-plug?) Look at the condition of cylinder #3's plug and parts compared to the others.

That the fuel additive helped could also point to intake valve buildup or a partially clogged injector. Follow up with Chevron Techron Concentrate at the next tank. CRC's "Guaranteed to Pass" is also an effective cleaner.
 

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I wouldn't jump to thoughts about compression issues or the like if the engine idles reasonably well and runs well under most conditions.

You logged a P0303 misfire code, so at least you have a place to start - a cylinder that's having the most difficulty. As Eagleeye already said, start with the basics. Plugs, wires & coilpack. (Just for my knowledge and because I'm feeling too lazy to go look it up, when did they switch to individual coil-on-plug?) Look at the condition of cylinder #3's plug and parts compared to the others.

That the fuel additive helped could also point to intake valve buildup or a partially clogged injector. Follow up with Chevron Techron Concentrate at the next tank. CRC's "Guaranteed to Pass" is also an effective cleaner.
legacy and outback EJ253 switched to coil on plug for the 2010-12 model year.

I think the last of the 2009-11 EJ253 impreza and foresters remained with plug wires and the old coil pack.
(2012 US spec impreza have the FB20, and Foresters got the first of the FB25B in 2011).
 

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I simply cannot abide useless people.
2006 2.5i and 2002 3.0 wagons.
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Burned valves are more of a neglected turbo thing. I wouldn't be concerned with compression until many more likely less complex things have been ruled out. It's like having a sore back and researching spinal fusion before strained muscle.

Check plugs and wires. A damaged wire will result in misfire. An oil coated plug will do the same, means you need new valve cover gaskets.

You can try another injector cleaner, especially if you have 100K miles of unknown quality fuel. I'm a fan of Gumout One-n-Done, it seems about the highest concentration of PEA one can currently find in a cleaner. Little spendy though. Chevron Techron, Gumout All in One, or Redline SL-1 are all good as well, usually a bit cheaper.
 

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Discussion Starter #9
Hi everyone, overdue for an update. I went on a bit of a wild goose chase with the P0303 code and the process was extended due to personal travel and vacation for the holidays.

I took it to a mechanic out here in Summit County, Colorado, (who was supposedly well reputed) and the guy tested the compression and found 75psi in cyl 3 and basically said it was too low and I needed a new engine. My worst fear was confirmed and it broke my heart so I let my car sit for some time and tried to take my mind off it. I later decided to get a second opinion because I was not about to throw $3000 for a new engine. The second guy said 75 isn't a bad number for a cold start and rather than re-do the compression test he looked at my spark plug in cyl 3. Lo and behold there was a fine crack in the plug, so he diagnosed that the plug was causing the issue.

I replaced all the spark plugs and wires with the most expensive NGK stuff ($38 for the plugs, $82 for the wires, and $200 for labor) and now my engine is running smoothly once again. Expensive but not $3000 expensive.

I also used the gumout fuel system cleaner and WOW my car runs so much better, so much more responsive to the throttle.

Unfortunate thing is now I'm starting to smell burning oil so back to the shop it goes.

I checked and I've spent somewhere around $4800 fixing up my car in the span of the year I've owned it. WTF!!!!!!!!!!! But I'll probably start another thread for that discussion. Ugh. I may be posting it up here for sale soon... :(

Anyways thanks for the input guys!
 

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$12,300 for the car? That's a lot. The problem with many cars is that at about 100,000 miles or 10 years, many cars reach the lifetime on a lot of components. The car can go 200-300,000 miles but a lot of things wear out near that 100,000 mile interval.

I bought my 08 brand new and really didn't do much to it other than change the oil and brake pads for the first 8.5 years and 120,000 miles (plus fix a torn CV boot). Over the past 2 years I've replaced the P/S pump, Timing Belt, valve cover gaskets, lower control arms, shocks and headgaskets. It was less than $1k in parts and I only had a shop do the headgaskets which was close to $1k in labor, I learned how to do everything else. From a cost/benefit stand point I could have gotten rid of the car at a good resale point at around 100k miles and everything would have "looked" good for another year or two.

The good thing for both you and me is that the work done to replace those parts won't need to be done again for quite a while. The bad news for you is that you are probably near the edge of the frustration level and another $1000 repair bill could put you over the top. I don't have much advice to give to you other than these things tend to happen with a lot of cars regardless of make or model. Mechanical parts just wear out and a 100k mile car may be good for another 30k miles or it may already be in the middle of the "endless repair phase".

Just be glad the bottom isn't rusted out, otherwise it really is time to ditch the car.
 

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A fine crack in the spark plug won't produce low compression numbers. However, it is easy to screw-up a compression test on the DBW cars (05+). If you weren't experiencing any other "lumpiness" or "engine rocking", usually compression is last on the list.

However, a good, confident compression check on all 4 cylinders would be nice data to have, especially at 120K miles.

On a semi-related note, has the valve lash been adjusted at all (either during or after the HG repair)? The higher mileage AVLS heads (06+) like to hold-open exhaust valves. Long term, combined with overheating, can cause the valve guide to drop and cause a loss of compression and fail a leak-down test. You will typically experience much worse symptoms than the "high load misfire", but it's a long term issue that should be addressed.
 
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