Japan Built 2002 XLE V6 Knocking when accelerates

[BlackCamSe]

Well my friend has a Japan Built 2002 XLE V6 and his trany or engine is knocking when he accelerates. He isn't exactly a car guy like he never changes the oil and stuff like that. I had checked his trany fluid and it was all dark and burnt and i know that isn't good at all. I checked the oil and it was fairly clean. I free reved it to 4000 rpms and herd know knocking. So my guess is that it is something wrong with the trany. Any thoughts?
BTW it has about 48,000 miles

[Forced Induxion]

is the knocking just a sound or do you feel it when accelerating? Knocking could sometimes be related to poor gasoline or engine oil. If you think the tranny fluid is burnt maybe you should do a complete drain/refill. Check service intervals. If he doesn't do oil changes thats a bad sign. Its pretty important to get the oil changed regularly because the viscosity of the oil breaks down over time and heat.

Start with trying a higher grade fuel and see if the knocking persists.

[BlackCamSe]

Well he told me that he doesn't feel it when he accelerates. He just hears it. And he recently had an oil change because i told him he needed it. And i think he will get a drain and refile on the tranny. Wouldn't it be a tranny problem because i free-reved it and it made no knocking.

[BlackCamSe]

[toyomoho]

The engine is under load when accelerating on the road, as opposed to being in Neutral. Try driving it and seeing if you hear the knock. See if it is a hammer knock; hollow sounding knock, ping, or gets louder when accelerating harder. Try accelerating in a different gear. The transmission will usually start slipping between shifts, fail to shift properly, act. But not knock. It also might be an axle joint. Does the car knock when making left or right hand turns?

Advise him to change both the trans and differential oil at the same time.

[Eye8Pussies]

what forced induxion said

sounds more like low octane fuel

what octane is he using? from what you said about him not being a car guy, I'd be that he puts in regular

the 1mz is fairly high compression, and can knock under acceleration when not using premium gas

[91MR2quickNA]

The 1MZ's knock sensors are extremely overreactive. If he's using 87 octane, the ECU retards the timing a good deal, but it could be pre-detonating if the gas is very poor in quality. Pinging is normal during hot weather and steep grades or heavy loading. Knocking is not, and that's where the knock sensors come in.

Rod knock is also more audible during idling because when the engine is loaded, the bearing slack in taken up. Once that bearing slack exceeds a certain point, the engine will begin knocking under load and eventually throw a rod. You said you heard nothing at idle and free-revving, so I wouldn't worry about an issue like that.

Many cheap gas stations sell 87 octane, but many times the actual octane rating is somewhat sketchy and closer to 85 octane.

When he fills up next, tell him to pull the EFI fuse at the gas station for about 10 seconds, and refill with 91/93 octane. See if it solves the problem. If not, you've got something else making noise that is similar to knocking. Could be a suspension component, a motor/transmission mount, or something of that nature.