stuttering sohc 2.5

Evan

Evan

Active member
my moms 2001 forester sohc 2.5 is having some issues. 160k miles.

she was exiting a toll booth on 95 and floored it to get around a car that was pinching her out of her lane. immediately after that the car was running poorly and jerking back and forth somewhat, poor idle, major loss of power, etc.

she pulled into the nearest exhaust repair shop (central maine motors) and had them replace the spark plug wires, plugs and fuel filter (to the tune of $180 labor + parts :angry4:). no better.

she gets it towed home and i test drive it the next day.

symptoms:

cold idle is mint

hesitates around 1500-2500 rpms, barely gains rpms, but will eventually 'come out of it' and take off closer to 3000 rpms. after warming up, it has a poor idle, including chugging/lurching and barely accelerates from a stop, but with enough thottle (not WOT) it will take off.

it seems like sometimes it drives well, and sometimes it barely works.

i replace the timing belt (thinking its due anyway, and she may have jumped the belt) it seems a little better, but still has issues.

after clearing the ecu, it has come back up with codes:

P0037: REAR O2 SENSOR HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)

P0137: Rear oxygen (A/F) sensor circuit range/performance problem

maybe its just the o2 sensor? its just odd that all this very suddenly happened when stomping the gas.

i'm almost sure my wrx has had that same code for the entire time i've owned it and it hasnt had an issue at all. and a lot of people defeat the code when tuning.

any help?

 
check plug boots for oil leakage, leaaky gaskets around plug hole in cam covers is a common problem area. CMM should have checked that when they replaced plug wires, but who knows

also sounds like may be a vac line issue...at 160k, hoses may well be dried/cracked/cooked and leak air causing erratic inconsistent driveability issues

 
i would check the opbvious like nigel said. but it sounds kinda like a o2 to me. but your right they normaly don't just go, they get worse and worse and worse.

 
i looked at all the vac hoses i could see, and they looked fine. i could have missed one though, but i looked all around the throttle body and whatnot.

while i was under there i didnt see any leaks around the heads (i was checking the head gaskets at the same time). i would imagine that replacing the wires and plugs would have at least temporarily solved the issue if it was leaking valve cover gaskets. and it cold idles fine, i would imagine a misfire from oil leak would be at all times and all rpms.

i might have her replace the rear 02 sensor, since it needs it anyway (according to the code) even though that may not fix it.

 
after talking to joel, inski and subie gal, i'm going to replace the front 02 sensor and hope for the best. $70 for the part and they have it on hand, so maybe my mom wont need to rent a car for the weekend :violent4:

 
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