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Miss fire on #4


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2010 LGT with great maintenance. Bought used with 60K. Now has 150K.

 

Got a hard misfire on #4 all the time.

 

Didn't think I had time to deal with it, so brought it to the dealership.

 

Within a 1/2 hr they called and said that it was a 'dead hole' and wanted me to authorize $1.5k/ 10 hrs of work to pull engine and diagnose. I asked if they had already done a compression test. Sales rep said, yes, they hooked up to the computer and it said that it was in the engine and they needed to tear it down to get to the cause. Wow! That's an amazing computer! There is no way they got a compression test done that fast.

 

Soooo... I am going to go it alone.

 

Steps:

1) get codes when I pick up the car (or use my own scanner)

2) See if moving coil on plug moves the fault

3) Any idea how to verify the signal to the coil is good if the fault doesn't move with the coil? Old fashion timing light (I don't have one)? Put in plug and look for spark?

4) Do the finger test. If no compression, buy a rebuild? If some compression, get a compression test kit and measure it for real.

 

Any leads on a place to buy a new or rebuilt LGT engine?

 

Thanks!

 

Tom

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  • 4 weeks later...

I bought mine used a few years ago with 105k on the odometer. It also had an intermittent misfire on cylinder four, after new plugs and coil packs all around, along with a new timing belt kit, it has been running like a champ for the past 10k.

 

It was not cheap, but getting quality parts from Rock Auto and doing the work myself kept the costs under $1k.

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Thanks! This isn't intermittent, it's continuous. Add idle and under acceleration. I did the timing belt myself at 110k a few years ago. Seems unrelated.

 

If it was intermittent I would be looking at the normal 'burnt valve on #4' scenario, but since happened suddenly and completely that seems unlikely.

 

I haven't had time to tear in to it yet. Probably have a few more weeks before I get to it. Lucky my son has a car that he can't drive yet! I'll have to get it fixed before he gets his license in Jan 2023!

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Thanks! This isn't intermittent, it's continuous. Add idle and under acceleration. I did the timing belt myself at 110k a few years ago. Seems unrelated.

 

If it was intermittent I would be looking at the normal 'burnt valve on #4' scenario, but since happened suddenly and completely that seems unlikely.

 

I haven't had time to tear in to it yet. Probably have a few more weeks before I get to it. Lucky my son has a car that he can't drive yet! I'll have to get it fixed before he gets his license in Jan 2023!

 

Something easy you can do is visually inspect the coil packs. My cylinder 4 coil pack was in really bad shape when I pulled it, the laminated metal was literally de-laminating. Hoepfully its not a burnt valve!

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  • 3 weeks later...

A big indicator would be; Is it eating more oil than usual? A broken/bent/ or burnt valve should make a for a pretty violent operation but shouldnt affect oil consumption. I would go in this order: Borrow a compression tester from Oreillys or Autozone. It's free. Check the compression on all cylinders. 4 will probably be low. If there is at least some pressure - shoot a tiny bit of oil into the cylinder and test it again. If the compression rises that means the oil helped seal a broken ringland. Cylinder 4 broken ringland is super common on these motors. Thats what happened to mine. If compression is good I would borrow a small camera from Oreillys (also free) and take a look at the valves. Either way the motor will need to come out if it is valves or rings...

 

I bought a brand new short block from Subaru for $1900. It comes with nothing on it but it is a brand new short block with brand new internals. It's not worth trying to machine and rebuild blocks on these cars. I had the heads cleaned and decked valves lapped and I reset the valve clearance. Not sure of your motor but mine is shimless buckets. It made it very easy to just remove material in thousands of inches of the inside of the buckets until the valve clearance is correct. (this will make sense once you start reading into it). It was a fun project and my car runs like a top now. Only specialty tools you I can think of you will need is some cam wrenches. Please keep in mind this is an interference motor and you could potentially slam the piston into an open valve. Make sure the pistons are at bottom dead center before removing the timing belt.

 

I hope this helps.

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  • 2 weeks later...

Finally did a little bit on this - Swapped plugs and coil pack between 3 and 4. Still misfiring on 4.

 

Next is compression test.

 

Thanks!

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Finally did a little bit on this - Swapped plugs and coil pack between 3 and 4. Still misfiring on 4.

 

Next is compression test.

 

Thanks!

 

Tdelker,

 

Make sure to label the cylinder positions your injectors are in and try those next if compression is normal. Good luck!

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  • 2 weeks later...

Dang it! 115 psi on cylinder 3, 15 psi on cylinder 4.

 

I didn't try the oil thing since the engine is horizontal it doesn't seem like it is going to help seal a ring. And I don't think it matters. Now that I know it's mechanical in the engine, it's a new engine for me. Pulling and repairing seems like it will take too long and a 60k used engine for 1.6k + shipping (probably around 2k total) seems like the right way to go.

 

Anyone bought from https://www.lowmilejdm.com ? Any other suggestions?

 

Thanks!

 

Tom

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  • 2 weeks later...
Dang it! 115 psi on cylinder 3, 15 psi on cylinder 4.

 

I didn't try the oil thing since the engine is horizontal it doesn't seem like it is going to help seal a ring. And I don't think it matters. Now that I know it's mechanical in the engine, it's a new engine for me. Pulling and repairing seems like it will take too long and a 60k used engine for 1.6k + shipping (probably around 2k total) seems like the right way to go.

 

Anyone bought from https://www.lowmilejdm.com ? Any other suggestions?

 

Thanks!

 

Tom

 

If I remember correctly the JDM engines have dual AVCS rather than just the intake...?

 

That would require tuning and other changes. Good luck!

 

IMO getting a brand new block from Subaru for $2000 and some elbow grease is the way to go.

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If I remember correctly the JDM engines have dual AVCS rather than just the intake...?

 

 

 

That would require tuning and other changes. Good luck!

 

 

 

IMO getting a brand new block from Subaru for $2000 and some elbow grease is the way to go.

You are correct. AVCS on all cams. The swap has been done, it's not impossible and even seems to work well. The main reason I did not go that route was the unknown of the engine I'd be getting, and availability of replacement parts. Some are the same as USDM engines, some are not. That being said, a short block from Subaru does not end with the cost of the engine and gasket set. At least, not done properly for maximum longevity. All in, with heads and turbo being rebuilt, all rubber hoses on the intake, all new oiling parts, I spent over $6k and did the work myself. To me it was not worth the investment but my son wanted to do it. He plans on keeping the car for a long time. Good luck with whichever way you choose. I feel your pain...[emoji17]

 

Sent from my SM-G892A using Tapatalk

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It's well worth the investment if you plan on keeping the car a long time. I've dumped 10-15k in to my 2001 Legacy over the last two years but... it's new on the bottom while showing a quarter mill on the cluster.
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  • 2 months later...

Well after more research, it appears people were correct, the JDM isn't a drop in replacement. It's hard to find that information, as it's all scattered around. But from what I have been told there are so many difference, and given my failure (exhaust valve burnt on #4) I opted to rebuild the heads for about the same price as the JDM replacement. Yes, the short block is still older, but at least I don't have all the headaches of an engine that I can't get parts for and having to get it tuned, and who know what else I would have stumbled on.

 

Both heads rebuilt = $1400 by super rupair in Boulder, CO. I should have shopped around more, but they could do them in the week, and they are very local, which made it easy. 

 

Parts were about $500 for gaskets, etc that are needed.

 

New timing belt (I have about 55k on mine) TCK328N from amazon at $200 (I was going to reuse it but I reconsidered, but needed to get it in a rush so paid a premium. Cheap options on there for the same gates kit).

 

I have a leak in the small 3-way hose that connects the PCV valve to the engine so I need to replace that. Local shop was thinking that a PCV leak could cause the burnt exhaust valve. Not sure I understand that, but it make me look closer as to why there was so much oil by the PCV and found that.

 

Engine back in the car but waiting on that hose and didn't have enough time to finish this weekend.

 

Total time so far is 4 pretty full days. Probably have 1 day left assuming it goes as planned.

This was my first time pulling an engine and taking heads off, so a lot of learning for me. I am anxious to see if I did it right!

I probably should get a smoke test done to ensure I don't have any other issues that could cause #4 to run lean and while I'm at it a conservative tune. I'll work on that once it's back up .

Tom

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What are people doing to figure out if they have a 'weak' injector? I can't seem to find a troubleshoot step to do this short of sending the injector off for test. Any hints?

 

I want to make sure I don't end up with a burnt exhaust valve again...

 

Tom

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Other than swapping injector locations to look for a problem following the injector, I think a bench test is probably your best bet. They will clean them as well as test them. You may enjoy the peace of mind that comes with just sending them off to someone. I don't know where you live, but sometimes there are shops in town who have the bench tester/cleaner and can do it in a few hours.

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Thanks Silverton. I saw some old threads about witch hunter and them being expensive. But given today's pricing, that's less than a single injector.

Do you have to pull the intake off or can you get to them with the intake on?

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Engine runs, no codes! (now)

Finished putting it all back together today. Forgot to put the heat shield on the drivers side on before installing the exhaust manifold so fought to get 2 screws in out of the three. Should have paid closer attention to the FSM, it clearly said to install it earlier. I didn't want to pull it as there are numerous crush seals in there (to the heads and to the turbo oil catch can). But it's on there good.

 

First start I got P0345. Dang it! Bank 2 (Drivers) sensor A (Intake). A check of the connector, and it wasn't on tight. I swore I wouldn't do that! But after that it was fine. Drove it about 10 miles, no codes, no problems.

Still want to do injector cleaning, a smoke test and finally a pressure test to make sure that whatever caused the issue in the first case isn't still there.

 

I'm not sure about the turbo. THere was a small amount of shaft play (not sure how much is too much - it wasn't hitting anything) and some oil in the intake and exhaust. $1200 for a new one. I think I'll play close attention and if I hear and sound, I'll jump on replacing it.

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