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Old 01-22-2008, 12:30 PM   #1
botboy
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Default End of my wits problems with '01 forester

Hi guys have problems, I'm a mechanic/lurker and not really a subie guy but my subie friends tell me this is the place to get advice and man, do I need it...

I'm at wits end with a car that came into the shop. '01 Forester L, AWD, 2.5, automatic

The car at idle, will "lope", that is the RPM's fluctuate slowly like the car has a big cam. I can smell that the car is running lean, it will lope slowly, then even out, and repeat. It does this even worse when stopped in gear

When trying to drive it, the car bogs down badly and has no power ,then will suddenly recover and accelerate like normal

As part of maintenance (car had been neglected when it came in) the plugs, wires, fuel, air filters have been replaced

another mechanic recently also replaced both 02 sensors

I've determined that the car is running lean, and starving for fuel when it bogs down by hooking a DMM with a duty cycle function to injector wires and having a coworker do a brake stand while I watched the meter. confirmed this by spraying a little carb cleaner into the intake while he was doing a brakestand, and the engine accelerated like it should. Fuel pressure stays constant, and within spec while this is happening. If the other guy stays in the throttle long enough, the car will recover, injector pulse will increase and the engine will accelerate as normal.

The car has no CEL, when it did set a CEL it was for 02 reporting overly lean, I can smell clearly the car is running lean at idle and elsewhere

in figuring this out, I've tried, with no luck, the following items:
- coil pack
- cam & crank sensors
- ECU
- TPS
- Map/intake temp sensor
- idle air control motor
- also tried the "grounding mod" mentioned elsewhere on this site
- removing exhaust
- disconnecting battery for 15 mins

I don't really know what else could cause the injector pulse to decrease with additional throttle/RPM. Anyone have any ideas? Bueller, bueller?
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Old 01-22-2008, 01:27 PM   #2
subikid
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any modifications?

Also, you might want to try rs25 in addition to this forum. rs25 is for nonturbo subies.

Good luck man.

Kevin
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Old 01-22-2008, 01:36 PM   #3
Matt Monson
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What you are describing sounds a lot like what my car does when the front O2 sensor starts to go bad. It will often do this without throwing a code. Maybe whoever did the sensor didn't really change it?
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Old 01-22-2008, 01:43 PM   #4
NYCBRED
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clogged throttle body??
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Old 01-22-2008, 02:06 PM   #5
bagelicious
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Make sure the battery is grounded well, stock subies sometimes have that problem.

probably too simple though.
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Old 01-22-2008, 10:16 PM   #6
yarrgh
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is air getting in somewhere other than your TB? clogged injectors?
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Old 01-22-2008, 10:28 PM   #7
PhilSine
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fuel pump or filter?
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Old 01-22-2008, 10:49 PM   #8
RaceFaceXC
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A vac or intake leak would cause the lean condition and lumpy idle... as for loss of power and injector pulse abnorm's i have no idea. Not knowledgeable with injector systems specifically. have you done a vac check or checked all the intake gaskets/joints? If you do figure it out, please let us know just for piece of mind and future reference. Hope you get some help.
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Old 01-22-2008, 10:52 PM   #9
sense of nature
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Quote:
Originally Posted by PhilSine View Post
fuel pump or filter?
Would be my first place to start
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Old 01-22-2008, 11:19 PM   #10
RaceFaceXC
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Quote:
Originally Posted by PhilSine View Post
fuel pump or filter?
wouldn't a bad fuel pump or clogged filter cause low fuel pressure?

Quote:
Originally Posted by botboy View Post
Hi guys have problems, I'm a mechanic/lurker and not really a subie guy but my subie friends tell me this is the place to get advice and man, do I need it...

I'm at wits end with a car that came into the shop. '01 Forester L, AWD, 2.5, automatic

The car at idle, will "lope", that is the RPM's fluctuate slowly like the car has a big cam. I can smell that the car is running lean, it will lope slowly, then even out, and repeat. It does this even worse when stopped in gear

When trying to drive it, the car bogs down badly and has no power ,then will suddenly recover and accelerate like normal

I've determined that the car is running lean, and starving for fuel when it bogs down by hooking a DMM with a duty cycle function to injector wires and having a coworker do a brake stand while I watched the meter. confirmed this by spraying a little carb cleaner into the intake while he was doing a brakestand, and the engine accelerated like it should.
Wont carb cleaner cause the engine to accelerate no matter what its condition?
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Old 01-23-2008, 01:55 AM   #11
ballitch
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Are you sure the "other" mechanic put the right o2 sensor in? I could be wrong, but I thought the newer siby's used a wideband front, whereas the older suby's use a narrowband. That could cause a problem. I would make sure you dont have any vacuum leaks.

If you know you have spark, and the engine gets power when you spray fuel into it manually.....and you say fuel filters and pressure is good......that would lead me to think the injectors could be clogged. Could also be the fuel pump relay going bad, even though i've never heard of that happening.



~Josh~
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Old 01-23-2008, 09:24 PM   #12
wirolla
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Quote:
Originally Posted by Matt Monson View Post
What you are describing sounds a lot like what my car does when the front O2 sensor starts to go bad. It will often do this without throwing a code. Maybe whoever did the sensor didn't really change it?
+12345....i agree.
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