Harsh Engine Knock - (not the usual tick)

I just completed my 25,000 mile scheduled maintenance on my Taco which included an oil change, tire rotation, and drive shaft greasing. After driving for about 10 minutes I noticed an extremely loud knock coming from what seemed like the engine. I pulled over and checked the oil immediately and everything appeared to be just fine.

The noise isn't the usual ticking that everyone seems to get, but a really loud knock like beating two hammers against each other. ALSO I can only hear the knock under heavy acceleration. The truck starts up just fine, and if I give it barely any gas I can't hear it. But when I try to get moving quickly the knocking starts up.

I currently have the truck with the Dealer, but they can not identify the source of the problem... Has anyone else had a knock similar to what I'm hearing?? Below are my specs:

4.0L V6
5 Speed AT
Stock Everything (Haven't got the $$ yet to make it my own )

 

Thanks for the reply! I used SuperTech (Wal-Mart brand) 5W-30 Full Synthetic, approximately 5 1/2 quarts. Yes I've changed my oil on all of my vehicles for the past 12 years, never had an issue before. This is the 5th oil change I've given my Taco, one every 5,000 miles using the same oil type. The dealer is able to recreate the noise I am hearing, and he has had his boss and his bosses boss hear it as well. None of them can identify the problem.

I can't hear the noise until I hit about 1500 RPMs when accelerating. If I accelerate very slowly to 65 MPH and the engine is running at 2000 RPM's but maintaining the same speed, I can not hear it. Only when accelerating.

The first time I started it up after the change I did notice a very small amount of white smoke, but since then I have not seen any smoke what-so-ever. This worried me at first because of the obvious implications, but since the smoke is completely gone I thought everything might be OK after all.

 

Bummer to hear man. Hopefully it can be figured out and fixed easily.
Off topic but welcome from Chantilly neighbor.

 

Engine knock is caused by bad plugs, wires, clogged or faulty injectors, timing. You'll have to check all the above. Crappy fuel can be a suspect too.

 

I've been running 87 Octane, but I did fill it up right before changing the oil so I suppose that is a possibility. Seems odd though because I've been using the same Shell Station for the past 1 1/2 years and never had a problem.

Chantilly eh? You must be 5 min away then!

Oswego: I didn't want to admit it, but it just so happens to be that yes, I did drain the tranny this time around instead of the engine... I knew it as soon as I pulled the plug. I was in a real hurry to get it done and wasn't thinking. Fortunately I was able to refill it using a thread that I believe I found here on this forum. I've driven the truck approximately 120 miles since refilling the tranny, and the ride has never been better (except for the noise of course). It shifts extremely smooth, and there is no hesitation when changing gears. Because the ride has been so smooth, I didn't even want to bring it up out of pure embarrassment, but your comment was just too coincidental.

 

I just received a call from the Dealer. They've tested everything they can (valve compression, engine scope, etc) and spoken with HQ about the problem but can't find any physical evidence that something is actually wrong. I'm picking it up tonight and hoping that its just bad gas. If it isn't, I'll drive it like I'm racing it until something finally does break and get it replaced/fixed via warranty.

 

Sucks they couldn't find anything wrong with it man. I've heard a lot of people mentioning draining the auto trans fluid by accident.
GL with the problem. Keep us updated if you find anything out.

 

Check everything! Oil, trans oil, and so on. Toyota dealers aren't gonna take the time to test drive your car. Trust me, ive caught them at my dealer and they said they took it for a test drive. Called em out on it and they finally took it for a drive. If you can find a Toyota specialist like i take mine to that would really help. The dealership is crap. But check that your spark plugs are gapped right, check fuel injectors. the smallest little thing will probably be causing it.

 

Put some dry gas(high percentage of isopropyl alcohol) and octane booster in the tank. Hopefully you didn't get swamped with water, just bad gas.

 

Well, regardless of whether or not they actually test drove it, I did get them to admit that there is a knocking noise and this was noted in the invoice I received. So if everything turns to shat I should be more than covered by my powertrain warranty. I plan on trying the fuel dryer, and re-checking all of the fluids.

As far as spark plug gaps and fuel injectors, these haven't been touched since I originally drove it off of the lot so I would rather let those be, even though there is a possibility that they could be the problem.

If I get any more information on it, I will be sure to post it back to this thread.

 

I've been driving the truck for a couple days now and the knocking noise is gone. As far as I know, the only change that was made by the mechanics at the dealer was resetting the computer, which from my understanding does have an effect on the firing of the spark plugs. If anything changes I will re-post, otherwise this will be my last post to this thread.