2002 Nissan Pathfinder engine knock

DERICKSON121212

MEMBER
2002 NISSAN PATHFINDER
3.5L
6 CYL
2WD
AUTOMATIC
200,000 MILES

After starting engine if you rev it up a little an upper engine knock starts that sounds similar to a rod knock but stops when it drops back to idle. Truck was running exceptionaly smooth every day on 30 mile freeway commutes everyday. Now I noticed knock right away at idle. But then just goes away or disappears at random. After getting on freeway I noticed knock seemed to be there continually for the most part right after putting in a new battery. When I stopped at light it stalled and so I went to restart and it acted as though battery was almost dead but then would start but a few miles down the road It started knocking bad to where I put on flashers and slowed to 25 mph. Note: I live in las vegas which right now temperatures have been 110 to 120 degrees every day for tha last several weeks please any ideas reply asap. And what is a knock sensor and what is its function?

6 Replies

WRENCHTECH

MECHANIC
20,761 POSTS

If it walks like a duck and sounds like a duck. It's probably a duck.

This car has 200K miles on it. You're pretty much reached the life expectancy of that engine and having worn out bearings could be expected at this point. Obviously I can't diagnose a noise over the Internet but that is a logical expectation.

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Wednesday, September 4th, 2019 AT 10:08 AM

KASEKENNY

MECHANIC
18,907 POSTS

Hi,

That is a pretty bad engine knock. If you run the engine much more it will most likely lock up or throw a rod through the side of the block.

Unfortunately, the only repair is to replace the engine or rebuild it. I would recommend replacing it because they are about the same cost depending on how much damage is done but if you go with a new engine it will come with a warranty.

If you would like to confirm this, you can drain the oil and remove the filter to look for metal flakes. Also, you can remove the spark plugs and use a borescope to look in the cylinders to see if there is scoring because this sounds like a piston knock or at least the lower end.

In the future you can start a new post with your specific issue. This works because it is the same type of issue but we like to get all your vehicle specifics and issue because it makes it easier for others to find similar issues. Plus it keeps the threads shorter. If we only had one thread for all these types of vehicles with engine noises it would get pretty long and confusing and people would stop visiting the site. Thanks for your understanding.

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Saturday, September 7th, 2019 AT 12:03 PM