914X4

I have a 91 V6 3.0 (3VZE) engine with only 172k.

I would like everones idea to the cause of this noise.

When the engine is cold' it is perfect - no knocking. When it warms up it starts knocking at 2000 rpm & up. It ONLY knocks when the accelerator is maintaining speed on level ground or very very slight acceleration or deceleration. As soon as I increase or decrease acceleration, the knocking noise is gone.

I bought the truck 1000 miles ago so I don't know the maintainence history. Thanks for your help.

95RunnerSR5

i dont have much expirence in this field but maybe your timing belt slipped a tooth? possibly seafoam could help?

1989toy4wd

Try higher octane gas, did you check the oil level? if none of that fixes it its time for a rebuild

Snipes4ever

I have a 93 V6 i just bought in March and it would do the same thing. It was fine when cold, but once warmed up, it had a knocking noise. I had a friend of mine who is a Toyota tech check it out and he used a long screw driver to listen to the engine, holding one end to the engine and the other against his ear. He listened to the bottom end of the block and oil pan and said it was for sure rod bearings. If you do this you can hear what is going on in the engine. I tore out the engine and sure enough, 3 out of 6 bearings were spun, i replaced them and now no problem.

gohawks

many will disagree with me more than likely. But had this EXACT same issue. I ended up finding resolution at another website where a certified Toyota tech answers 3 questions per day.

According to him this is a common issue on high mileage 3.0's (this is where some will disagree with me).

What has happened is that there is a little bit too much clearance in the front main bearing. When the oil warms up it becomes thin and under load you get some main bearing knock under load.

What has to happen is to replace the front main bearing with the right sized bearing (one with the least amount of clearance that Toyota makes), then replace the rest of the main and rod bearings with one size less clearance than what they came with (you can only tell by getting the pan off what size they are).

Now, there are two ways to do this, none are cheap.

1) pull the motor, probably the best, and just freshen everything up
2) drop the differential, drop the oil pan, pull the transmission back and do the job from underneath (this is the way I had it done, good luck finding a mechanic who will do it for you if you can't do it yourself).


or you could just put a "new" motor in.

I think it cost me something in the ball park of $1200-$1400.

Toyota bearings are expensive, but I wasn't going to take a chance with anything other than OEM since they are a select fit bearing.

My knock is gone, my wallet is light.........good luck.

I did ask the guy how long you could drive it that way..on average.

He drove that way for a LONG time...but added any excess clearance is a bad thing, and you never know...I had a long trip planned so I went ahead and fixed it.

gohawks

https://www.yotatech.com/forums/show...t=main+bearing

link to the thread I had after the fix

914X4

But wouldn't bad rod bearings make noise at ALL rpm, ALL the time when warm? (That is all throttle positions?) I only get the noise above 2000 rpm and ONLY when throttle is maintaining speed on flat road or slowing at a rate of 1 mph/10 sec - If I let up or increase throttle the noise is gone.

Could this be an exhaust leak? Exhaust Valve?

Yes I have ran both high & low octane & FI cleaner for 3 tanks. I changed the Oil after purchase, I still have good level & does not leak or burn any oil.

Please keep posting your ideas. Thanks

914X4

thanks gohawks, I was typing when you were typing. Did your noise go away when you put the engine under heavy load? My noise only happens at no load, it disappears when under load or using the engine to slow down.

I am puzzled, I am familiar with main & rod bearing knock (but not toyotas)

Bumpin' Yota

mine had been doing the same thing noise wise but is completely dependant on ignition timing and octane gas put in...

At 15*btdc with 87 octane it was insane pinging. 93octane and 10* btdc made the pinging go away for the most part. If it was foggy or raining, no pinging ever. Conclusion carbon depositions in my case which I just confirmed today. I pulled the passenger side head off (driver's side blew its HG) and OMG carbon EVERYWHERE!

kmcc78240

So would seafoam elminate that carbon?

Bumpin' Yota

Honestly I dont know about sea foam, it cant hurt. Unless you suck up 1/2 a can at once by dropping the brake booster line completely into the can....one of the members here did that and hydrolocked his 3.slow. If you use the booster line, just add it drop by drop so its vaporized or relatively so.

I know water will though! lol However WMI is kinda hard to justify on a NA engine so as to clean carbon out...

Other than that, probably pulling the heads.

But as was suggested it may also be rod knock...

914X4

tks'
any other ideas out there?

yota_krazy

most likely the front main bearing as said earlier. I have also heard this from a toyota master tech. I have also heard that the oil pump puts more strain on the front main bearing. Has anyone else heard this?

excableguy

I drive a straight road to and from work, and my '94 (22RE, though) would make the same noise whenever i gave it a little gas or when the truck was just kinda "cruising" with no load on it. It drove me crazy and after a couple of timing chain set change outs and multiple tune up ideas,I gave up and pulled the motor like my mechanic buddy said, and found that my mains and my rods were spun @ 84k. sorry hope it's something else for ya

Bumpin' Yota

Gohawks - why did you have to pull back the transmission from the engine to change the mains?

gohawks

I didn't do the work myself, a mechanic did. What I was told (whether that was the truth or not) was that there was a protrustion on the main seal lip that prevented you from being able to access the back of the bearing cap (being a one piece cradle). So you had to pull the transmission back.

Now, I have been told by some this is true, I have been told by others that no, this is not the case.


914x4...mine was under load, albeit a very slight load ~900-1200 rpm.

Here's what you need to do....get the engine nice and warm (20 min of driving). Then put it in gear put your foot on the brake and slowly give it some gas. If you have that "thump thump thump thump" at low the lower RPM then I say excess clearance in front main.

gohawks

Bumpin'

I forgot to mention I have the auto, if that makes a difference. I don't know if it is an issue with a manual or not.

Bumpin' Yota

Right now im in the middle of a top end rebuild so I dont know if I have that issue or not but the block does have 276,000 on it. At last recollection when I did that it would just sound like you were giving it more gas.

Of course with the block without the heads it IS temting to yank it all the way out...lol I too have the auto.