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2005 Forester XT Manual
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37 Posts
Discussion Starter · #1 ·
I know this is my first post, but im currently in the middle of reading multiple threads with other users having the same issues

First of all I got this forester (very) used 207k miles. I have about $8k worth of service records (that came iwth the car) that i've gone through once, but will b going through again to help better determine my next course of action. The engine was rebuilt around 19Xk mi, plugs and wires have been changed, the MAFS looks fairly new, and I have personally changed the upstream o2 sensor (disconnected the batt to reset ecu) and the issue(s) are still there

P0302-cyl 2 misfire
P0304B-cyl 4 misfire
P0420-Cat below threshold bank 1

Of course, im feeling the bucking and hesitating of the misfire(s), but does run better with warmer weather outside. Also if u drive it like a grandma, car runs fine. Sometimes the cel is flashing (mostly during the misfires) but otherwise constant. Running rich/poor gas mileage etc.

If its a cat conv issue, i will drill it out at this point as long as it wouldnt negatively affect the vehicle.

Any advice will be greatly appreciated!
 

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2005 Forester XT Manual
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37 Posts
Discussion Starter · #2 ·
mini update: i decided to reset the ecu by disconnecting the pos and neg terminals, applying the brake (and horn for good measure). I also cleaned off the terminals, clamps, and (since i heard about bad grounding issues) the ground by sanding them to insure good contact/ground

Result: cel is off/cleared (may b a temporary thing) because there's still a slight miss (but does drive better)
 

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Discussion Starter · #3 ·
i feel like im talking to myself, but heres another update.

Car seems to had A.D.D. If i reset the ecu, cur runs great up to about 20% throttle. Seems like if i got past a certain point/load that it will cause a miss. 2 days later miss occurs and cel flashes and comes back on. (while it was off i was ableto get 28mpg driving 115mi round trip.)

But once that CEL is on, misses all over the place. Any thoughts anyone?
 

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1999 L 4AT
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1,222 Posts
timing or ignition.

remove the timing belt inspection cover and see if the belt marks are aligned properly. the belt may have slipped a few teeth and that's what is causing the misfires.

if the belt is good, then I'd suspect the coil.
 

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2005 Forester XT Manual
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Discussion Starter · #5 ·
yeh, i read a youtube vid that may've suggested the timing belt slipping.

Ive looked at the work/maint. records and the coil,plugs, and wires have all been replaced along with the mafs, and i did the upstream, so yeh that may b the culprit
 

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1999 Forester S 5-Speed Manual
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217 Posts
Your codes alone have already spelled it out, I believe.

P0420 - Catalyst below efficiency threshold (Bank 1): Your catalytic converter is clogged. The clog is causing backpressure in the cylinders, thus the misfires, poor throttle reponse, and hesistation. Keep driving it in this condition, and you risk engine damage.

Your best bet at this point: Replace your cat and all spark plugs. Use an OEM Direct-Fit coverter - Aftermarkets may cause the Check Engine Lamp to stay on and thus fail Emissions Testing.

The spark plugs should be replaced due to the misfires. I'm assuming the damage so far has fouled them up.

An oil change wouldn't be a bad idea, either. Get her running nice and clean again.

I know it sounds extreme and that it COULD be something else, but I'm doubtful this is the case. What you're describing is EXACTLY what happened with my old 2003 Hyundai Santa Fe. By the time I ruled out everything else, I ended up damaging the camshaft from excessive backpressure and replacing the cat and plugs was too little, too late. Luckily I was doing a Rent-To-Own from a local dealership on that car, so I was able to return it to the dealership and owe nothing, nor have it affect my credit score doing so (they didn't run credit checks).

Good luck.
 

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Discussion Starter · #8 ·
ok thanks. I was thinking about doing the cat. but its just weird how resetting the ecu make it run close to fine.

and yeh i agree about the plugs. i konw theres a quite a bit of disscussion on which ones, but any standard (decently priced ones) i can rely on?
 

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1998 Forester Manual
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14 Posts
I'm a Denso slappy. Have had them in everything to economy cars to our 640HP Supra.

Denso IK20. Might outlast the car. :)
 

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1999 Forester S 5-Speed Manual
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217 Posts
ok thanks. I was thinking about doing the cat. but its just weird how resetting the ecu make it run close to fine.

and yeh i agree about the plugs. i konw theres a quite a bit of disscussion on which ones, but any standard (decently priced ones) i can rely on?
Until the ECU relearns idle and fuel trim, it runs in a "loop", bypassig the O2 sensors and thus less backpressure.

Sent from AutoGuide.com Free App
 

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2005 Forester XT Manual
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37 Posts
Discussion Starter · #11 ·
hmm thx for the input. im sure at over 200k miles the cat could very well b clogged
 

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Discussion Starter · #12 ·
Well, finally a decent update:

friday i put this in (help take care of that clogged cat ;) ) It definately helped it out A LOT but still had the misfire if i went above a certain throttle percentage it felt.



So today i did plugs and wires and this is what i found. Just another testimate to "dont use autolites." Surprisingly the XPs were the better ones than the regular copper ones, but still they were bad and porcelain was cracked. I replaced with NGK V-power Coppers. Fos runs like a champ now (i hope for a while)


 

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2012 Forester 4 speed auto
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1,173 Posts
It's the coil

It's the coil that fires cylinder 2 and 4. This is a DIS waste spark system, so if a coil fails it fails in 2 cylinders. Nothing wrong with the spark plugs if there isn't a spark they act like corks on a bottle. Too bad the misfires wasted the converter you might have a problem passing the smog test. Good luck.
 

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2005 Forester XT Manual
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37 Posts
Discussion Starter · #14 ·
so if they fail again replace the coil? How long should these last then?

btw we dont have emission regulations here.
 

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2012 Forester 4 speed auto
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Ground strap

After reading this thread very closely, since the engine was recently rebuilt check to see if the re builder re attached the grounding strap that goes from the engine block to the car frame. I see you checked the grounding terminals on the battery. However, some times the grounding strap on the engine isn't put back in place after a rebuild. DIS ignition coils need to be grounded. :cool:
 

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2005 Forester NA Auto
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3 Posts
I had a similar problem with a 99 Honda and it ended up being the distributor cap. It was chipped and causing the exact problems you describe. Sounds like you got it figured out, just wanted to throw out some other possibilities.
 

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2005 Forester XT Manual
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Discussion Starter · #17 ·
After reading this thread very closely, since the engine was recently rebuilt check to see if the re builder re attached the grounding strap that goes from the engine block to the car frame. I see you checked the grounding terminals on the battery. However, some times the grounding strap on the engine isn't put back in place after a rebuild. DIS ignition coils need to be grounded. :cool:
ok, srry im still new to foresters, but where should i look to see if they reattached the grounding strap?

thx all for the input. if it happens again, ill be replacing the coil
 

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2012 Forester 4 speed auto
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1,173 Posts
You can always make one.

Look for a braided wire strap long and narrow connected on the engine, usually the valve covers, to the frame. If you don't find one you can make one with 8-10 gauge wire and two round hole crimp connectors. Using existing screws on the engine and frame, you ground the engine. A lot of mechanics forget this strap when they reinstall the engine because they don't understand its purpose and it doesn't cause a problem right away.
 
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