I have a 2002 Impreza RS 2.5 with 105,000 miles on it. No engines issues to date, except for last night...

 

All of a sudden on a back-road an engine knock started along with a loud grating / high pitched sound. If I accelerate substantially, the engine gets rather rough, indeed. Oil level is fine, as is transmission fluid levels.

 

I dug further and found what looks like a wire junction with two leads, one of which seems severed.

 

Here is a photo:

http://www.flickr.com/photos/blakespot/12057583596/

 

And here's the max zoom on that photo:

http://www.flickr.com/photos/blakespot/12057583596/sizes/o/

 

Can anyone tell me what exactly those cables and that white, plastic junction box are? Does that look right to you? Thanks much.

 

 

 

 

 

bp

That is the knock sensor connector.  Normal.  Only 1 wire, although it is a 2-wire connector.

Was the timing belt ever done on it?

First off, do not start the engine again until you find out what it is.

105k miles is the timing belt interval. So if it hasn't been done, I'd start looking there. If the timing idler gears (cogged in particular) or the tensioner piston fail it can make a terrible knock. 

I had one so bad i thought I was about to put a rod through the block, but it turned out the tensioner was losing pressure and just flopping around.

Timing belt was done at 70K.

 

 

bp

Screaching and knocking sounds like a failed timing idler. The one with the teeth is the one that likes to fail. Pull the timing cover and take a look.

Did you (or whomever replaced the belt) change all the idlers, waterpump, and tensioners? Either way, if you have a terrible noise coming from the engine you need to start looking somewhere. And that's an easy place to start.

That's an auto trans, right?

 

Does it make the noise in neutral/park, or only in gear?

The other thing that makes terrible noises is a cracked flexplate.

 

Or it could be a spun rod bearing.... but hopefully it's something easier.

Edited January 21, 201412 yr by 987687

x2. don't start it or drive it until you know the issue. Pull the timing covers and check. I had a sprocket go bad a couple months ago. had to do a timing job in a dennys parking lot.

 

Lucky though that the engine was okay.

Dealer just got back to me. Apparently the timing belt skipped 4 notches. It was replaced around 68K miles. ~110,000 on the car now. Mechanic doesn't know how it didn't snap. Pressure, etc. tests show no damage to engine, though. Also, a rear pulley is going bad, so replacing all four. 

 

Thought I'd update, for those interested.

 

Thanks for the suggestions.

 

 

 

bp

Sounds like they didn't do it properly the first time around...

dealers don't do proper timing belt maintenance unfortunately and they charge a massive premium for their low grade service in this regard.  if i or a quality independent would have done it, you'd never have had this issue. replace all 3 timing pulleys, the tensioner, and the belt with every timing belt change.  the tensioner should be replaced as well, the new style is not that reliable and yours has seen multiple compressions/installs now.

 

i'd also replace the belt, it may have been compromised by the jumping of teeth and it's 40% done (40,000 miles on a 100,000 mile belt). 

if the dealer charges $500 to replace a timing belt (i know a dealer in maryland that charges $699) - then you're 40%, or $200 into that.  might as well spend the $59 on a new belt now and new pulleys and be done until 210,000 miles.

 

Gates kits are used by many who do lots of Subaru work and only cost $125 for everything:

http://www.amazon.com/Gates-TCK328-Timing-Belt-Kit/dp/B0033DM4UA

MAKE SURE TO REPLACE THE WATER PUMP!!!!

It's driven by the timing belt as well, and is not likely to last another 105k miles 'til the next timing belt service interval.