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2001 Forester- EJ25 SOHC

Ran fine before I removed the motor for head gaskets, various seal replacement, rear access panel reseal, new spark plugs, etc. Heads surfaced and cleaned, but I did not take the cams out or do anything with the valves. Put it all back together and...had a loud knock from the left head. Drove fine; plenty of power; no issues beside the knock. Put about 30mi on it. Next morning, started up fine (knock still there). Drove it about 1mi and it started to lurch and lose power. Barely made it back home after stalling and restarting with decreased power. Parked it and the catalytic converter was glowing red hot. Today, 3 days later, took off timing belt cover...still timed correctly with belt tight and pullies and tensioner working. Started it...motor quiet without the loud knock, but is now rocking from side to side. Confirmed spark from each plug wire. Removed exhaust from heads and found oil in #3 valve area all other clean; #3 plug very black. 

  • knock
  • hot CAT
  • rocking motor
  • oil in exhaust

Any ideas?

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Could something (nut,bolt) have fallen in the head while reassembling ?  Hot cat sounds like its dumping fuel in # 3 for some reason.  Check compression I bet #3 is low. Maybe you bent an intake valve ?  

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why the hedgasket work? leaking externally, or was there an internal leak into the coolant?

 

overheating events? how many and how severe?

 

kinda wondering if the tensioner was the source of the knock sound, but not sure why it stopped. How old is the tensioner? If re-used, was it compressed very slowly? Any oil on tiop of it's cylinder? it can sound a lot like rod knock - but it may get quieter with RPMs or kinda come-and-go at different RPMs. Rod knock usually get louder and more agressive with higher RPMs. do you recall what it sounded like?

 

misfiring in #3 dumped unburned fuel into exhaust. Cat may be damaged and blocking exhaust now. Dunno why the misfiring - valve seals?

 

 

lots of guessing, sorry = hope someone else has better ideas.

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Knocking could be timing belt tensioner slapping. Inspect that.

And it doesn't have to be slapping much to make that noise!

 

Cheers

 

Bennie

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