P0303 Misfire Needs New Engine? Please Advise!!
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This is a discussion on P0303 Misfire Needs New Engine? Please Advise!! within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I bought a 2002 Wrx wagon (all stock) with 63,000 miles last December. Everything was fine and dandy until I ...

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    Red face P0303 Misfire Needs New Engine? Please Advise!!

    I bought a 2002 Wrx wagon (all stock) with 63,000 miles last December. Everything was fine and dandy until I towed ~2000 lbs across the country with a UHaul last summer. I don’t know whether the towing was responsible, but a month later my check engine light went on for the first of many times.

    P0303, misfire cylinder 3. When I took it to my mechanic they first told me I needed a manifold sensor and mass air flow sensor. That didn’t do the trick, and they found that cylinders 1 and 3 were at 70 psi, and the vacuum pressure was off and wavering. Spent about two grand getting the cylinders removed, remachined by a machinist, and replaced.

    A month later, light back on. Reflashed the computer software. Another month later, light back on. The mechanics started to feel bad for me, and replaced spark plugs, cleaned fuel injectors, and changed the coils around for no charge.

    Another month, another check engine light with misfire cylinder 3. This time they took it to the Subaru dealership, measured the compression in the cylinders to be 140, 140, 150, 160. They said it will continue to misfire occasionally (especially at lower temps) and said there is nothing else they could do except for replacing the engine. They recommended I continue driving it until the engine starts knocking loudly and I notice significant deterioration in performance, which they said could be 2 months or 2 yrs. They said it should be pretty safe to drive, and that I would clearly notice noise as the engine gradually dies on me.

    I don’t feel particularly safe driving with the knowledge that my engine could go at any time. I look at the money I’ve dropped already as sunk costs, as I’d rather have my Wrx in like-new condition (it has 83,000 miles and is otherwise in great shape) for about 4 grand (if I go with a used engine) than just about any car on the road. If I can drop 4 grand on it and get 5 more solid years out of it, I would probably cut my losses and take that.

    I’m really hoping to get some advice on this situation:

    I’ve checked the forums, and it seems that the misfire cylinder 3 code is something that tons of people chase after, and few seem to fully resolve. I think my mechanics have tried everything mentioned in the forums. Is there anything else to seriously consider, considering my mechanic and the Subaru dealership are out of ideas? Should I take it somewhere else for another opinion?

    As this seems to be somewhat common in the Wrx, as well as other high revving 4 cylinders, is it worth the risk getting another engine? I was thinking something between 50 and 80 thousand miles, going for about $2500 with another grand or a bit more for installation. Should I spend more to try to find a younger engine? What model years fit my ’02 Wrx?

    Any advice would be hugely appreciated!
    Thanks,
    Rob
    Last edited by goblue; 02-22-2009 at 01:10 PM.

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    really? nothing?
    I don't mean to pester you folks, but I could really use some advice, any advice, from people who know more about this stuff than I do. I really love this car but I don't want to throw good money after bad.

    Should I cut my losses, consider myself SOL, drive it till it blows and go into debt to buy a new car? Should I avoid long distance drives because it could blow at any moment?

    Or should I consider the money I've spent already as sunk costs, get a used engine, and hope to get another 5 yrs out of the wrx? Or should I take it to another mechanic for a third opinion?

    If I do get another engine, how many miles should I be looking for? What model years have the same engine as the '02 wrx? any advice on best ways to find a reliable used engine?

    Any advice (or even sympathy?) would be greatly appreciated!

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    Admiral Ackbar mycologist's Avatar
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    Yeah, that does suck. I would consider the money you put into the engine as sunk, the rest should be good. You could look at this as an opportunity to get a nice motor in there. The one thing I am confused about is whether they are saying the misfire is due to the bad compression? You need to make absolutely sure that if you put a new motor in there it isn't going to get damaged. You could do some logging to make sure everything is running properly.

    No one can guarantee you another 5 years, who knows if the tranny will go next etc. But, it sounds like the car is worth another motor to me for sure.
    "From a little spark may burst a mighty flame." - Dante
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    Registered User EvoEatr's Avatar
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    Your 100% positive the car is 100% stock...Ive heard of light weight flywheels and lightened/underdrive crank pulleys throwing off the crank sensor and causing problems like this...also do you notice the car misfiring or is it simply the sight of the CEL?
    Last edited by EvoEatr; 02-22-2009 at 03:53 PM.

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    thanks for the replies, fellas.

    EvoEatr, yup, I'm sure everything is stock.

    mycologist (and others?),
    I got some more detail from my mechanic that might clear up the confusion. They say there are 2 factors causing the misfire:
    1) the 20 psi split btw/ cylinders
    2) extra clearance (about 2-3 thousandths of an inch!) between the connecting rod and the crankshaft. apparently this causes the rod to rock back and forth on the crankshaft, particularly when cold, and then the gap expands when it heats up. The knock sensor then picks up noise and retards the timing. They say this excess of movement and the piston rocking (stopping and going back) will wear away the bearings and cause bigtime problems in the future.

    I guess it's a chicken or the egg thing as for which caused which or came first, but towing 2000+ lbs from ME to AZ may have been directly or indirectly responsible.

    I don't know if this adds any pertinent info, but going above 5000 rpm seems to make my CEL blink. When I turn off the engine and on again the light is solid. Everything else seems to feel ok except for a really rough idle (that I noticed after towing).

    Again, both my mechanic and Subaru insist the only solution is a new engine, and they insist that the problem can only be engine related (so if I get a new one everything should be dandy). Does that sound right to you guys?

    also, mycologist, what do you mean by replacing with a finer motor? Like what? my understanding is that unless I want to pay an (additional) arm and leg to rewire the harness and a bunch of other stuff, I have to go with the same wrx engine from '02-'04. My top priority now is saving cash, along w/ reliability and then fuel economy (if anything can be done about that). 227 horses is plenty for me. Am I missing something?

    Again, any advice is greatly appreciated.
    thanks a bunch,
    -Rob
    Last edited by goblue; 03-03-2009 at 10:11 AM.

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    Admiral Ackbar mycologist's Avatar
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    I believe that you can use an EJ25 or EJ207 with just a tune (you won't get the avcs to work on the 207 though). I'm not absolutely sure on this. Also, do you know if your heads are reusable? If so you could get a rebuilt shortblock for the stock EJ205, or maybe do a hybrid. I guess though with your stated goals I would just get a 205.
    "From a little spark may burst a mighty flame." - Dante
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    Moderator Donkey's Avatar
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    It's a common problem on the 02-03 WRX's.You can buy a Tactrix cable and reflash the ECU with a stock ROM with the appropriate changes for the missfires.I actually used my car as a test mule for this change.

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    Donkey

    Thanks for the reply Donkey, but I'm not sure what you're recommending. Are you saying to do this with my current engine? Won't that just prevent the CEL from coming on without fixing the problem (meaning my engine will still blow in the near future)? Or does this actually somehow compensate for the misfire (meaning I wouldn't have to get a new engine!)?

    Would you please elaborate?

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    Quote Originally Posted by goblue View Post
    Thanks for the reply Donkey, but I'm not sure what you're recommending. Are you saying to do this with my current engine? Won't that just prevent the CEL from coming on without fixing the problem (meaning my engine will still blow in the near future)? Or does this actually somehow compensate for the misfire (meaning I wouldn't have to get a new engine!)?

    Would you please elaborate?
    What I'm saying is the 02-03 ECU's were very sensitive to misfires.A lot of them are phantom events.If you mechanics have done everything as far as testing fuel pressure and swapping injectors (just like the coil packs) and still can't find anything then this would be the way to go.Not sure why they replaced your MAF and MAP sensor.They should refund your money for those and give you your old parts back.I love the dealership techs "replace it 'till it's fixed" diagnostic methods.Unless your getting a flashing CEL,these misfires are far from destroying your engine.They are merely hiccups.Trust me.I have been around awhile playing with these cars.There is a reason someone spent ALOT of time writing code and disassebling the ECU just to figure out the misfire fix in Romraider.
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    hmmm

    Donkey, so you're saying I should ignore the 20 psi difference in cylinder compression, the clearance gap causing the knocking, and the really rough idle? What about the fact that my CEL blinks when I go above 5000 rpm? Is this safe? If it'll continue to get worse, I may as well get a new engine now and get some enjoyment and peace of mind out of the car, right?

    Something real seems to be going on (rather than phantom signals) because this issue originally caused damage to my cylinders requiring them to be remachined (which now seems like a waste of 2 grand, but I don't think I can do anything about that).

    If I can drive my car safely and get rid of the CEL (as long as it will still turn on or blink when it really needs to) I would love to not spend 4 grand on a new engine. What do others think about this suggestion?

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    Moderator Donkey's Avatar
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    Quote Originally Posted by goblue View Post
    Donkey, so you're saying I should ignore the 20 psi difference in cylinder compression, the clearance gap causing the knocking, and the really rough idle? What about the fact that my CEL blinks when I go above 5000 rpm? Is this safe? If it'll continue to get worse, I may as well get a new engine now and get some enjoyment and peace of mind out of the car, right?
    I missed the blinking CEL above 5000 part.20psi between which cylinders?Hopefully the new ones are not reading 140psi.Did they do a leak down test?

    Quote Originally Posted by goblue View Post
    Something real seems to be going on (rather than phantom signals) because this issue originally caused damage to my cylinders requiring them to be remachined (which now seems like a waste of 2 grand, but I don't think I can do anything about that).

    If I can drive my car safely and get rid of the CEL (as long as it will still turn on or blink when it really needs to) I would love to not spend 4 grand on a new engine.
    Yeah definalty not phantom signals.For 2G's you could have had a brand new factory 2.5L short block.Not sure why there are clearance issues.It's not like you can't buy oversized rings and rod bearings.
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    hybrid question

    thanks for all of the advice, folks.

    So I just spoke w/ my mechanic again.

    It probably was a rod bearing issue from the get-go, and I probably wasted $2000 on having the heads remachined. They said that the rod bearing problem is hard to spot, and they suggested at that point that an engine swap was the safest way to go. Maybe they should have spent the time/money to check the bottom end in more detail and push the full engine swap at that point, but oh well, there's nothing I can do now about that.

    I asked about the hybrid option, as several folks here and on Nasioc have suggested, of using my heads with either an ej205 short block or upgrading to the sti short block, and they said that would cost more than twice as much in labor ($2500 vs $1100) and could lead to further detail issues and misfires.
    They said the most economical and safest/reliable approach would be an engine swap w/ a low mile full engine of an '02 wrx.

    Does that sound right to you all? Why is everyone so gung-ho about the hybrid idea? Is it supposed to be that expensive or is my mechanic missing something?

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