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2002 Impreza Outback timing belt ques ?


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7 replies to this topic

#1 jdemaris

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Posted 15 November 2010 - 09:11 AM

I just bought a 2002 Subaru Impreza with the 2.5 engine. So, it's a flat Boxer four - two cylinders per bank/side. One cam per head - so two cams total but called a SOHC engine.

Ran perfect but had 110,000 miles with no service work ever done. Still had original spark plugs, timing belt, water pump, etc.
OK, no big deal, right? I've done many, many timing-belt jobs - but this time I have a problem.

I installed a new "Cloyes" belt and idlers along with new water pump. I thought I check timing marks correctly several times before putting back together.
Started it, and it now sounds like an old Chevy I stuck a hot cam in. Idles lousy, but smooths out at higher RPMs. I drove it and a drive-speed, it seems to run fine. But . . now a engine-check-light has come on. I checked the codes and it says "misfire on cylinders 1 and 3." PO 301 and 303.
1 and 3 are both in one bank. So, if the timing belt was off a tooth for the one bank - it would effect only that bank and two cylinders.
I hate to second-guess myself, but also tend to believe in "cause and effect." It ran fine before, and now does not. Only other things I did, was pull out the old spark plugs - after this problem - and found the gaps at .090". I put in the new plugs gapped at .044". It did not fix this problem. I was a little worried that I might of screwed up a plug wire due to the long plug boots that go into the head. They come out hard. But, I can't see two going bad all-of-a-sudden, and they check out at 5000 ohms each, which ought to be fine.
Anybody ever driven an engine with one bank slightly out of time (valve timing, that is) ?

#2 GeneralDisorder

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Posted 15 November 2010 - 10:05 AM

Do you have spark on those cylinders? If so do you have fuel (injectors ticking)?

If you have both of those run a compression test. If it's low then you probably have the belt on wrong.

GD

#3 johnceggleston

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Posted 15 November 2010 - 10:07 AM

links below with timing belt info.

it is possible you used the wrong timing marks. it is a common mistake.

good luck.

> FOR TIMING BELT ARTICLES CLICK HERE

> great timing belt pictures - click here

#4 grossgary

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Posted 15 November 2010 - 11:04 AM

nice job cranking out the timing belt job yourself! hopefully you get this figured out quick and simple.

probably got the timing off. could even be just one tooth off on one side.

also - EJ engines are notoriously sensitive to ignition components - so wires wouldn't surprise me either. i've seen brand new aftermarket wires cause cylinder misfires. if you replace, use Subaru only on those.

but given the recent timing belt i'd start there. you can at the very least double check both cams by just removing the side timing belt covers - those are easy to remove and only take a couple minutes. you won't really be able to verify the crank sprocket but you can see if both cams are lined up properly.

older vehicles have an alignment mark on the flexplate/flywheel too so you can check it under the throttle body through the bellhousing access hole, if you can do that with an EJ you might not have to remove the crank pulley and center timing cover to check that.

#5 jdemaris

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Posted 15 November 2010 - 01:05 PM

Do you have spark on those cylinders? If so do you have fuel (injectors ticking)?

If you have both of those run a compression test. If it's low then you probably have the belt on wrong.

GD


Seems to be plenty of spark. I just read in a forum that many aftermarket belts have the timing mark for the right-cylinder-bank one-tooth off. I'm wondering if that's what's happened here? My error codes say "misfire" on both right-bank cylinders. I'm calling the passenger side the right-bank - with #1 and #3 cylinders.

Question : If this has happened due to having the one cam one tooth off - how does the engine know? Better put, what sensors are able to detect poor combustion in just those two cylinders and throw out the two error codes PO 301 and 303?

#6 GeneralDisorder

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Posted 15 November 2010 - 01:15 PM

I would imagine that it's reading the knock sensor output and not seeing the pulse from it at the appointed time of ignition - the ECU is programmed to ignore knock sensor signals that are a direct result of cylinder combustion - but what people don't realize is that the knock sensor plays a "tune" that is sort of..... electronic music for the ECU. If the ECU sees a note being played where it shouldn't then it can detect a detonation or "knock" and adjust the timing appropriately, but the correlary to this is that if the ECU *does not* see a signal when the spark plug fires or that signal is different than expected it determines there is a misfire at the cylinder it just triggered.

Also - NEVER go by the marks on the belt. They can be wrong - ALWAYS use the timing marks on the cams and the belt covers. I just ignore the belt marks if they have them. Many of the belts I have bought don't even have them - which is just fine with me.

GD

#7 Mike104

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Posted 15 November 2010 - 02:36 PM

I would imagine that it's reading the knock sensor output and not seeing the pulse from it at the appointed time of ignition - the ECU is programmed to ignore knock sensor signals that are a direct result of cylinder combustion - but what people don't realize is that the knock sensor plays a "tune" that is sort of..... electronic music for the ECU. If the ECU sees a note being played where it shouldn't then it can detect a detonation or "knock" and adjust the timing appropriately, but the correlary to this is that if the ECU *does not* see a signal when the spark plug fires or that signal is different than expected it determines there is a misfire at the cylinder it just triggered.



GD


GD, while not asked by the OP thanks for this explanation of how the ECU detects Misfire. I have read various posts about misfires and I wondered how the ECU detected these, now I know! :banana:

#8 jdemaris

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Posted 15 November 2010 - 03:42 PM

nice job cranking out the timing belt job yourself! hopefully you get this figured out quick and simple.

probably got the timing off. could even be just one tooth off on one side.


I've got 40 years experience as a mechanic, but it's mostly diesel or "old tech" for cars. With this 2002, I don't even have a full shop manual.

I've had countless Loyales and Justys over the years. 1.3s and 1.8s. Also a 95 Impreza 2.2. Put belts in all of them and no problems. But . . . they all had timing marks on the engine -not on the belt.

So, now I'm perplexed. I just pulled it all back apart. With the crank-mark pointing up, the driver's-side cam mark is straight up. But, the passenger side in NOT. It's about a tooth's worth pointing to the passenger-side fender.

So, I gotta ask - does anybody know, 100% for sure - what the tooth count is on this engine. SOHC 2.5 in an Impreza Outback 2002 wagon. Right now - the passenger-side cam sprocket to crank-sprocket is 48 teeth. The driver's side cam sprocket to crank-gear is 44 1/2 teeth.
This does not seem to agree with any info I've found so far on the web.

New belt is a Cloyes B307 and says "223 teeth" on the box. The old Subaru belt I took off no longer has any marks on it, to compare with.




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