Q: Engine knock/pinging

asked by on September 22, 2016

I'm hearing a knock/ping when my car is idling, but when i rev in higher rpm i don't hear it. It is a 2005 Toyota Isis Platana with a 1az-fse vvti engine. The knock/ping has been there since I bought the vehicle 3-4 months ago. It hasn't gotten any louder and the engine is not losing power. Watch the video here : https://youtu.be/8EZEwMqJj1U

My car has 160000 miles.
My car has an automatic transmission.

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That sounds like a lower end knock. Which would be a rod or main bearing. The first thing to do is make sure it has oil in it. I expect it does since you state the knock goes away when you rev the motor. There are a couple things that need to be done to be sure what it going on. Before I describe them, I have a few things you need to consider.

Does the knock occur when the motor is cold? Does the knock become louder the longer you drive it? Is the knock only there at idle?

Oil pressure will be at its highest when the motor is cold. If the knock isn’t there then, this would be consistent with an excessive clearance issue at the crankshaft. When your motor is warm, the oil pressure is at it lowest especially when it is at idle. When you rev the motor, the oil pressure increases and the knock goes away. Eventually you will need to replace the rod and main bearings. If your inclined to do this kind of work, I suggest doing it sooner than later. It can be done by simply removing the oil pan. If you wait to long, you will need to remove the crankshaft, which essentially is an engine rebuild. You can also use thicker oil. This is of course the simplest method but it isn’t a permanent fix.

If the knock becomes louder as you drive more, you may have debris in the oil pan that is slowly sucked into the oil pick up screen which will clog it, starving the motor of oil. If this is the case, you will likely hear the upper end make noise as well.

To get a feel for how bad it is, I would feather the throttle at a high idle attempting to make it knock as hard as I can. I know this doesn’t sound good, but unless you were to do this for hours, it won’t make anything worse. When you feather the throttle, you want to make the RPM’s rise and fall in about a five hundred RPM range. As you rev the motor higher, it will exhibit a rapid knocking that goes away as the RPM goes above a certain RPM. Keep in mind, this is simply a diagnostic tactic designed to measure how much play is in the lower end. It does take some playing with the RPM to get the maximum effect.

If you feel you need to, connect an oil pressure gauge where the oil pressure sensing unit is and do a direct test of the actual oil pressure.

If you should need further help with this, I recommend having one of our mobile technicians diagnose the noise from engine for an accurate repair.

Good luck!

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