Loud Engine Knock Under Load

I’ve tried just about everything at this point. I have a 2005 mitsubishi outlander that’s at about 165,000. At the beginning of the year, it started developing a small knocking sound and it’s gotten progressively worse to the point I don’t feel comfortable driving it. It only happens when the engine is under load, usually going uphill. I used to think it was affected by the rpm’s but I’ve since decided speed of the engine does not affect it. It’s really quite loud and rhythmic. The only time it seems random is when I let off the gas a little going up hill. It sounds great at idle and I can rev it up to 3500 rpms in neutral without any problem whatsoever. The weirdest thing to me is that I don’t feel like there’s any loss of power. If I was completely deaf, I wouldn’t suspect any sort of issue.

Here’s what I’ve tried so far:

-Replaced timing belt, balancer belt, and pulleys
-Replaced VVT solenoid
-Cleaned out the EGR valve
-Replaced the fuel filter (though not sure if this would actually affect anything)
-readjusted the valve clearance

  • changed oil

There was no change after each of these things

Other possibilities I suspect could be the issue:

-Bad knock sensor
-carbon build-up (Plan to try the seafoam cleaner)
-bad rod bearing
-blown head gasket

  • Vacuum Leak

I’d appreciate any input as to what to attack next. Thanks!

If the vehicle has an automatic transmission, remove the starter/access plate and see if the flex plate is cracked.


It ended up being a blown head gasket unfortunately. Got it all fixed now though. Thanks for the help!

Good to hear back from you. Thanks!