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Old 09-08-2012, 04:52 PM   #1
SubieWolfSti
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Subaru Banner Cyl. #4 Diagnosis and Repair Expirience

Hello,

I have Cyl.4 misfire that im fixing, i thought it would a good idea to share my expirience with everyone who has the same P-code at least .

Of course it started with a code, however it ran good just a rough idle. After looking at the Flash data the code was trigger a low or idle RPM. I read the service manual but noticed it assumed it was an ECM communication problem when going through the steps.

I checked for air leaks and found none.

I swapped the coil, injector, and plug and the misfire didnt move, so that eliminated the hardware. I used a noid set to check for pulse, and COP pickup for signal from the coil, all was good the pulse and coil wavelength were perfect.

Did a compression test and the figures were 1. 140, 2. 129. 3. 133, 4. 125,
Did a Leakage test and the figures were 1. 2% 2. 2% 3. 2% 4. 11%
So there is a problem with Cyl 4 from these figures, however the compression and leakage are still within limits so they shouldn't cause a miss.

This isnt mentioned in the manual but it should be. As time passes and mileage increases the valve clearance between the cam and lifter are shortened, therefore the valves become tight, if anyone has owned an old vw, they would know what a tight valve does...causes a rough idle, and missfire . At least they tell you how to adjust it and check it.
I check the valve clearance on Cyl. 2 and 4, Cyl 2. Intake .008, .008 Exhaust .008, .006
Cyl. #4 Intake .010, .010, Exhaust .010, .000

Conclusion Cyl. 4 has a tight valve. Needs adjusment.

Hope this helps all you guys and girls out there.
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Old 09-08-2012, 07:56 PM   #2
Jkmaynard
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I am going thru this same problem can you please tell me how to check the clearance i have done everything from swapping fuel injectors coil pack plugs fuel filter pump vacuum leaks and my misfire has stuck with cyl 4
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Old 09-08-2012, 07:56 PM   #3
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Ps also my compression test was good i have not done a leakdown yet
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Old 09-08-2012, 09:10 PM   #4
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Sure no problem, i do recommend you buying the subaru service manual because it gives you all the necessary procedures to fix the valve clearance as well as the part numbers for the different lifter thickness.

All you need is a feeler gauge set to check the clearance, you remove the valve cover (Get ready to buy a valve cover gasket) and turn the motor until the cam is on the Heel on the lifter. Then use the feeler gauge to check the clearance. All this is in the service manual, good luck.

The Spec is
Intake 0.0079 +or- 0.0008 inches
Exhaust 0.0138 +or- 0.0008 inches

When doing a compression test make sure its on TDC, and also that the piston doesnt move (I put it in reverse and put the parking brake on so it doesnt move.)

Last edited by SubieWolfSti; 09-08-2012 at 09:13 PM. Reason: Add a bit more stuff
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Old 09-09-2012, 05:00 AM   #5
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Sorry if this sounds dumb TDC, ? lol and who do i buy the service manuel from does Subaru sell them? .

Sorry for the dumb questions i am just at my wits end with my 06 REX i want to kick it to the curb i have been chasing this misfire problem for well over 4 weeks...

Damn misfire will be on for days drive like crap then Bam go away and run like a dream for 10/15 miles or so then come back
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Old 09-09-2012, 11:41 AM   #6
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you download the manual from here:
http://ken-gilbert.com/impreza-manuals

TDC = top dead center
although if you didn't know what that was, chances are you aren't ready to be taking valve covers off

best of luck
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Old 09-09-2012, 12:00 PM   #7
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did any of you have any air pump codes? I also got a few intermitted lean codes too while diagnosing. I ordered 2 new exhaust valves and lapped them and installed the proper buckets. runs like a champ now. all in all it was a pretty easy fix. I spent more time trying to find info on pulling the intake manifold than it took to tear down and rebuild. oh and sealant is your friend when bolting the valve covers back on
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Old 09-09-2012, 12:14 PM   #8
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I should have signed up for NASIOC earlier and i would have gotten the manual for free but oh well, i got mine on ebay.

I will offer a bit more advice as to the difficulty of this repair. Its pretty hard, if you do have to adjust the valves, at that point you will need the special tools to remove the cam intake and exhaust sprocket. In addition, you will need a torque wrench, a micrometer that can read to .0001 of an inch. There is math required to calculate the new lifter thickness.

I dont know how much the dealer wants for the repair, but just to give you an idea, so far with spec tools and the seals and gaskets for that particular job all OEM parts im in $1,070 but i intend to build a few Subie motors so the tools will pay for themselves.

Most impotantly be honest with yourself, do you feel comfortable to perform such a repair? Do you have the tools? Keep in mind your removing the timming belt, and Camshafts therefore you have to set them up yourself, a few teeth off or setting the cam the wrong way will kill your motor so be careful.

I just wanna make sure you dont bite more than you can chew, because this is a big bite. I would suggest the dealer because they have everything, even though they may be expensive, your in safe hands.

Good Luck
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Old 09-09-2012, 12:19 PM   #9
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I havent had any air pump codes but im still waiting on the lifters to come in. Ill keep ya posted. If any come on after im finished with the Job
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Old 09-09-2012, 03:02 PM   #10
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Ooooo i did have a secondary air injector stuck open but it wouod come on then go away gor a month come back for a few day then go away again...

i know the dealer will bend me over backwards on this fix i wonder if it will be the same from a mechanic i was just planning on doing a timing belt and water pump at the same time
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Old 09-09-2012, 05:21 PM   #11
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Well although the dealer charges an hefty price lets do a comparison...
The Dealer...
Is expensive as hell, but...They have the right tools, use OEM parts, have the manual and expirience. In addition you have a significantly higher probability of getting your car running right the first time, and you will get your car back sooner.
The Mechanic
Unless they specialize in Subaru, they lack the equipment, take too many shortcuts, lack expirience with the car, it could stay at the shop way longer than it should, and they might break something and say it was already broken and charge you for it...or mickey mouse the job and most likely the car will have more problems or comebacks to the shop. And use the cheapest parts to replace the seals, gaskets or use the old ones again . They might even tell you need a new motor
Of course not all shops are like that, but sadly many are...i would find out how much the dealer wants for the job so you have a guide as to what to do. Friendly tip look a the mechanics tool box, if its a cart of just one toolbox, chances are he doesnt have the tools for it but before anything look into that air problem, and check the valve clearance thats the cheapest route.
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Old 09-09-2012, 06:10 PM   #12
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The air problem is really annoying it is a huge problem on 06 07 wrx's the dealer fixed it 2 times while it was under warranty seems to come back every 30K miles or so...

And we do have a specific Subie mechanic about 15 miles from me who has been in business for about 25 years family owned might give them a call
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Old 09-09-2012, 06:55 PM   #13
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i will agree with subiwolf if you dont feel your comfortable doing the repair id leave it up to the pros. i did mine after reading the manual several times and i still had to call a subaru tech to clearify some things. id go to a tuner before taking it to a subaru service. i ended up doing timing belt at the same time. i spent about a 1g on parts and an accessport after it was all said and done. i even got them to throw a stage 1 map with airpump delete.
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Old 09-09-2012, 09:48 PM   #14
SubieWolfSti
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Thats good news that you have a specific subaru repair shop, depending on their volume they may even lease an OEM factory scanner which is the most awesome subie toy for diag, and testing
I would still ask for a price from the dealer and use it as a reference, sometimes independent shops are only a few bucks lower than the dealer other times its a lot cheaper but same quality service.

Last edited by SubieWolfSti; 09-09-2012 at 10:37 PM. Reason: Spellcheck...
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Old 09-09-2012, 11:54 PM   #15
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Lol if your mechanic doesn't know how to check valve lash, he needs to step away from the tool box and find a new career. Checking/setting valve lash on a DOHC Subaru is not difficult, but it is labor intensive. It doesn't require any specialty tools.

Subarus seem to be tough on the valves/seats. I've seen several with tight exhaust valves, and the early signs are a rough idle.
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Old 09-10-2012, 02:54 AM   #16
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I had no early signs of it running normal straight to crap with cyl4 misfire that will sometimes go away for about 15 miles and then come back and run like crap again
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Old 09-10-2012, 01:44 PM   #17
SubieWolfSti
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Well only one way to find out if its the valve clearance or not and thats to go have it checked

Being a high mileage car im sure the probability of it hapening is very high. The only thing that confuses me is that checking the valve clearance isn't part of the service interval for subaru . I guess they figure it would never need one, but then again why would they offer intructions on checking it and adjusting unless it were for rebuild purposes only, or so they thought
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Old 09-10-2012, 02:53 PM   #18
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Keep us updated when you get it back together and how it runs
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Old 09-10-2012, 03:46 PM   #19
SubieWolfSti
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Oh i definately will, the lifters should arrive on thrusday according to the dealer, so hopefully i will have it running by this weekend.

Meanwhile i will play around by making some interior pieces from my Sti out of carbon fiber hopefully it looks good.
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Old 09-19-2012, 02:52 PM   #20
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Just an update...

I put the new shims together, some of the clearances didnt match up so i had to order a few more shims to get it right, For now i have to wait for the parts to arrive to put my car back together.

On a more depressing note, Cyl. 4 exhaust valve was tighter than previously measured. Since the clearance was pretty much zero. i didnt know exactly what shim it needed. After checking the clearance with the new shim, i still needed .0028 more to meet the spec. The problem here is that they don't make a shim with that small of a clearance so i had to choose the smallest shim they had to come close to the spec.

This will fix the problem but, it also means that ima need a new head later on because the clearance is beyond spec.
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Old 09-20-2012, 12:30 AM   #21
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Quote:
Originally Posted by SubieWolfSti View Post
Just an update...

I put the new shims together, some of the clearances didnt match up so i had to order a few more shims to get it right, For now i have to wait for the parts to arrive to put my car back together.

On a more depressing note, Cyl. 4 exhaust valve was tighter than previously measured. Since the clearance was pretty much zero. i didnt know exactly what shim it needed. After checking the clearance with the new shim, i still needed .0028 more to meet the spec. The problem here is that they don't make a shim with that small of a clearance so i had to choose the smallest shim they had to come close to the spec.

This will fix the problem but, it also means that ima need a new head later on because the clearance is beyond spec.

That really sucks but at least if you can get a couple more years out of it that will help while you decide what to do with the motor
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Old 09-20-2012, 04:13 PM   #22
SubieWolfSti
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Well im thinking of removing that motor and putting it in my 70 beetle, and building a stroker motor for my Sti that way i get twice the fun. The motor seems fine its just one head that will need to be replace later on, but by that time i'll rebuild the whole thing for safe assurance.
Kinda interesting that Cyl #4 runs hot on Subaru but on air cooled Vws its #3 that runs hot, i wonder if it could be the different firing order?...Kinda interesting.
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Old 09-27-2012, 05:38 PM   #23
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Update

Well i put everything back together, i set all the clearances to spec and it started. I drove it around, and it runs like a champ. The check engine light hasnt come on and everything looks to be in working order.

Advice: If your planning to do this job, make sure you have the right tools, follow the manual and do the math to pick the right bucket shim, other wise your left with expensive extra shims that are not returnable.

Good Luck.
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Old 09-27-2012, 07:20 PM   #24
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when you get to the point of rebuilding the heads you most likely will not need a new head as the machine shop can replace the seat and/or tip the valve this is the removal of a small amount of the end of the valve some shops do this as a normal way to adjust the clearance of the valves just for your infor. jim
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Old 09-28-2012, 06:59 AM   #25
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Quote:
Originally Posted by SubieWolfSti View Post
The only thing that confuses me is that checking the valve clearance isn't part of the service interval for subaru
The lifters are hydraulic. They are supposed to take up clearance with oil pressure.
Just curious, did the factory procedure call for you to check the clearance after the oil drained from the heads?
I wonder how long that may take with a synthetic oil and capillarity keeping it in place..
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