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91 loyale, 98 forester, 99 impreza, 02 outback, 10 forester
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5 Posts
Discussion Starter #1
Problem with 02 outback 2.5 shudders under load. Approx 143K. Trans shifts smooth. Plugs/wires replaced, no change. Only happens after car is warm, perhaps 20-30 minutes of driving. Not noticeable at idle or low speed 45mph or less. Suspect u-joint in rear drive shaft. Have placed FWD fuse and will be driving car tomorrow to see if it changes. I have read slightly older outbacks had u-joint problems. Filters(all) not replaced. Orig pcv, egr, maf, 02. Trans/dif fluid, clean and full. Slight oil leak on plug chambers, planning to replace vc gaskets. Vacuum lines/coil no cracks no arcing. Any ideas would be greatly appreciated before i start tearing her apart. I say u-joint because if you let off gas you feel a slight jump almost like slack or momentary reversal of a driveline component. Thanks in advance.
 

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03 H6 OBW & 06 WRX Sportwagon
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17,553 Posts
clean or change PCV

throttlebody cleaning (maybe the seafoam with the spray, U shaped nozzle)

check the knock sensor for cracks

OEM plug wires? Denso? soobs have a reputation for rejecting cheap wires.
 

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91 loyale, 98 forester, 99 impreza, 02 outback, 10 forester
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5 Posts
Discussion Starter #3
put new vc gaskets on both sides. changed fuel filter. changed oil, air filter. put new coil on and added seafoam to crank and fuel. cleaned new plug wires and plugs of oil residue. using ngk wires and autolite double platinum plugs. new air filter. pcv valve is stuck, changing tomorrow also with a new battery. gonna check differentials again. possibly change tranny filter although fluid is very clean. it appears electrical, the FWD fuse did not make a differnce. i realize all the driveline components still spin, but still think its electrical or possibly torque converter(hope not). will post tomorrow when i get a chance to drive.
 

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01 Outback H6 VDC, 97 GT wgn w/ ej22, 98 OBW w/ej22
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1,401 Posts
some have referred to this as a hiccup, does that sound like what you have?

clean the throttle position sensor, or replace it, both the electrical connections and the the stuff in side. spray it all with the electrical contact cleaner.

BE SURE to mark the position of the unit before you remove it so it goes back EXACTLY the way it was. they have to be adjusted just so and marking it will save work and head ache.
 

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91 loyale, 98 forester, 99 impreza, 02 outback, 10 forester
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5 Posts
Discussion Starter #5
Items replaced so far: coil, plugs, wires, vc gaskets(not too difficult and changed oil after), battery, pcv valve, fuel filter, tranny filter(had one anyways), front rotors, air filter. This engine already has the new head gaskets. Problem persists, no change. At least I have a tuneup somewhat complete. My hunch the whole time has been drivetrain but its difficult to diagnose, when i crawl underneath the rear shaft seems tight. You can really only feel it under load while warm, it feels like a misfire but im not throwing any codes, but then again im not sure this vehicle would throw a misfire code. I am going to run the scan tool on it tomorrow or Tuesday to check the specs. As soon as you let off the gas it goes away. Power braking does not reproduce the problem. After scanning i will check the TPS. Any other ideas? I know the 98 forester throws a knock sensor code occasionally but if im not mistaken the Outback has the gen 2 2.5.
 

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91 loyale, 98 forester, 99 impreza, 02 outback, 10 forester
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5 Posts
Discussion Starter #6
Looks like we may have a bad cv joint. Having the car raised tomorrow to diagnose. Started clunking pretty bad during a right hand turn over uneven terrain. Will post results after.
 

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91 loyale, 98 forester, 99 impreza, 02 outback, 10 forester
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5 Posts
Discussion Starter #7
Problem solved. New half shafts in front, new set of tires. Drives like a new one. Thanks all.
 
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