05 LGT with P0302

Hey guys. Hoping to get some input on another P0302 issue.

 

My car is a 05 LGT manual with stage 2+ and 120K miles. CEL is on and cylinder roughness goes up to 99 when I come to a stop and sometimes before. It starts as soon as the idle comes down from a cold start and doesn't really change as the engine warms up. Car shakes and I can hear a misfire when the cylinder roughness is going up the scale.

 

Coil pack was changed but a used part was put in so I'm ordering a brand new OEM part. Spark plugs are only 10K miles old. I'll also try swapping injectors.

 

The strange part is that the idle roughness smooths out after about 1 minute of idling and roughness goes away almost completely. I can idle the car for ten minutes after the initial roughness and it won't go much past 5 or so. However, if I start driving and stop again, it does the same thing. Does the fact that the idle does this consistently point to any specific item I should be looking at or should I just go through the steps and plan for a new engine?

 

Also, it seems like this is a pretty common problem with these cars. I've read some threads where a new engine was put in and the problem came up again shortly after. What do you think are the chances of that happening? I'd hate to put thousands into a new block if there's a good chance I'm just going to have to do it again.

 

Thanks in advance for any insight.

Have the black o-rings between the TGV's and the intake manifold been replaced with the newer thicker orange ones ?

 

Next test is to swap coil packs and see if the CEL follows, if it doesn't swap injectors and see if that helps.

Have the black o-rings between the TGV's and the intake manifold been replaced with the newer thicker orange ones ?

 

Next test is to swap coil packs and see if the CEL follows, if it doesn't swap injectors and see if that helps.

 

Thanks for the ideas Max. I've been reading your rebuild thread and it's helped a lot. Injectors swapped and brand new oem coil pack and plug were put in and still the same problem. So I guess I'm looking at another engine.

 

Mechanic has a 30K mile long block from a totaled Forester that he's willing to sell me. Other than compression and leakdown on that motor is there anything else I should request for to verify the motors health?

 

Also, since I'm only getting the long block, is there anything else, other than change the turbo, that I should do as preventative maintenance?

 

Thanks again for any and all help.

Have you performed a leak down test on your engine yet? I’d start there and then if you have a lot of leak on #2 pull the valve cover and check valve clearance . You may only need to adjust your valve clearance. I had similar symptoms. Unfortunately mine turned out to be bent #4 exhaust valves.

Have you performed a leak down test on your engine yet? I’d start there and then if you have a lot of leak on #2 pull the valve cover and check valve clearance . You may only need to adjust your valve clearance. I had similar symptoms. Unfortunately mine turned out to be bent #4 exhaust valves.

 

 

 

Thanks for the input Dave. Unfortunately I’m the type that always has a ton of bolts left over whenever I work on a car so a shop is taking care of it for me. The labor costs for diagnosing this issue are starting to pile up and I’m starting to worry that I’m just spending money to find something that is a known problem with these motors. Wouldn’t the shop need to pull the motor to check the valves?

 

Just as a side note, no smoke comes out of the oil fill tube when the car is idling but a bill placed over the tube flutters violently if that means anything. I’m also losing a quart of oil per 3k miles. But gas mileage is fine and no smoke at start or driving.

 

Thanks again for any help.

 

 

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I’d at least have them do a leak down test on #2 to see where the problem is if there is a mechanical problem. They should be able to determine whether it leaks through the intake valves, exhaust valves or past the rings. No need to remove engine to check valve clearance.. actually plenty of room to work once the valve cover is off.

 

 

 

Just as a side note, no smoke comes out of the oil fill tube when the car is idling but a bill placed over the tube flutters violently if that means anything. I’m also losing a quart of oil per 3k miles. But gas mileage is fine and no smoke at start or driving.

 

 

 

These are all pretty normal for these engines...they do consume oil

So my shop is offering me the 30K mile long block for a great price so I think that it would make sense to go that route rather than trying to get the heads rebuilt. I'm going to get compression and leak down done and also send an oil sample out to blackstone labs. Anything else I should do to verify the new motor's health?

The leak down and compression test will tell you what's going on. It's possible that you are losing cylinder #3, unless there is a vacuum hose leak causing this issue, the tests will tell.

So have they checked the valve clearance yet? 30-45mn job for an experienced mechanic IMO.

Compression was 120 across the board so they said it most likely was valves. They are quoting 1.5k - 2k for the rebuilt heads or I can get the 30k mile motor for 2.8k installed instead. Since my motor has 130k miles it makes sense for me just to go with the 30k motor. Keep in mind I am in a small town so there’s not a lot of places to go for options. Do you think rebuilding heads would be the better route?

 

 

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Sometimes, it is just a matter of addressing the valve clearance issue if it is not too late (i.e. burnt valve). I have shared this several times: I have two turbo Subies, both of them suffered from similar symptoms. And for both of them, it ended up being a very tight exhaust valve (zero clearance left). This means that the valve was not really able to seal very well. In any case, I fixed the issue myself twice and both times cost about $300 worth of parts (timing belt related parts, valve buckets, etc..). I have added about 30k on both cars now. Misfires are still gone. Some food for thought.

Sometimes, it is just a matter of addressing the valve clearance issue if it is not too late (i.e. burnt valve). I have shared this several times: I have two turbo Subies, both of them suffered from similar symptoms. And for both of them, it ended up being a very tight exhaust valve (zero clearance left). This means that the valve was not really able to seal very well. In any case, I fixed the issue myself twice and both times cost about $300 worth of parts (timing belt related parts, valve buckets, etc..). I have added about 30k on both cars now. Misfires are still gone. Some food for thought.

 

 

 

I really do appreciate the insight. I wish I was mechanically inclined. I changed the #3 coil pack myself and damn near fainted when the car actually turned on after.

 

I’m leaning towards the new motor just because I swear my car was built after hours on a Friday. I’ve only had it 6 months and anything that can go wrong has gone wrong. I swear my car is actually trying to kill me. It’s sad because my last subie ran like a raped ape and was trouble free for almost 10 years.

 

 

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So the oil analysis on the used motor came in everything was normal. Compression test and leak down are pending. Assuming those come back normal than I'll be swapping that motor in.

 

Just a quick question, since the motor is going to be out do you think getting the heads rebuilt for $500 would make sense? They only have 30K miles on them but I'm a little hyper sensitive since I'm in this mess because of a burnt valve. Or do you think just checking and adjusting them would be enough?

 

I'm also getting a rebuilt vf-52, changing out the engine mounts, making sure banjo bolts are removed, and having all vacuum and fuel lines zip tied. Anything else I should do along the lines of preventative maintenance I should be looking at?

 

Thanks again for any and all help.

Heater hoses should be replaced as well as the ground wires from both heads to chassis.

 

Cobb AP or open source and custom tune for the vf52. I assume you'll be doing a catted 3" down pipe ?

 

Do you need a clutch kit or is it a 5eat ?

 

Hang around here long enough and you can learn how to do the easy jobs as DIY.

 

The ground wires are easy to make up or NAPA has some ground wires for about $10.00 each. I made my own from terminals and wire I had laying around the house. wire brush the surface and then seal the connection with RTV sealant.

 

Also wire brush the grounds under the two bolts on the bar at the back of the intake manifold under the brake booster.