Im not sure how long this went on for but my engine does this knoking sound when it is cold. If it stands and idles for about 10-15 min. it stops. Im not sure where it is comming from, could it be the pistons? If anyone has any ideas what it can be please help me out. Is it harmful or can i still drive fine even if it does that? Is there any thing that can help it like some kind of engine additive?

 

Are you using 87 or higher octane gas? If not, try it.

 

no im using octane rating 85

 

Is there any other problems that can be with it?

 

What oil are you useing and do you keep it and the filter changed?
Forgot to ask how many miles are on it? What engine is it? It could be that you are due for a valve adjustment. Mike

 

85 octane???? You should be running at least 87.
Its possible that its just piston slap. My F-150 has a knock to it during the winter time but once the engine comes up to temperature the noise stops.
Cap'n

 

The engine is the v6, 3.0, 3vze. I am using castrol gtx high miledge for the oil and napa gold filters, i change it every 3-5 thousand. Right now i have 157k on my engine.

 

Can't afford octane 87 or higher

 

Most likely it's piston slap. Which basically means the piston is rocking in the cylinder. As the piston warms up, and expands slightly, the clearance between the piston skirts and the cylinder wall is reduced, and the rocking is minimized to where it's no longer audible.

Piston slap is often caused by revving a cold engine hard. The pistons are cold, and haven't expanded yet. So as the engine is revved, the skirts can actually be deformed inward, causing the piston to rock in it's bore, or "slap".

As for additives to add to the engine, nothing you can pour in the engine will reshape the pistons.

The only way to fix it, is to install new pistons. And then be careful not to work the engine hard, until it's warmed up.

That being said, engines can usually run a long time, even with piston slap at cold start-up.

The 85 octane gas is what is used at high altitudes, instead of the 87 used at low altitudes. The higher in elavation you go, the less octane you need.

 

huh? It only adds up to a couple more bucks per month-if that.

Anyway, thats why i asked. When I first bought my Runner (same enigine as yours with 170,000 miles) I had the same problem. It would ping in the cold but go away when warm...etc. I was using 85 octane gas at the time and then i read in the owners manual....it says to run 87 or higher. I switched to 87 and believe it or not, i havent heard pinging ever since.

edit: btw, i just noticed your in CO...do you go off roading very often? If so, where?

 

could even be a wrist pin either way unless its hammering it could run a long time if you are easy on it.

 

I agree about letting it warm up. Some guy's think that 10 seconds is long enough to warm an engine but it's not even close. Let it warm up until the idle starts to lower ,
I like about 5 minutes in the summer and much longer when it's cold out in the winter.
If you let it warm up the engine should last you a long time yet.
I've never seen higher octain take care of piston slap but I do know it will take care of valve rattle. On the older engines it really made a difference on the lifters rattleing in the mornings. Mike

 

Check and make sure your K&N intake is totally sealed. I did the ISR Mod and for a long time I had to keep retightening it to make sure the seal was tight. When it heats up and everything expanded it ran smooth as silk again.

 

my 93 3.0 3vze also knocks a bit on cold starts here in maine (during the winter, and also cold mornings at other times in the year). as soon as it warms a bit it goes away and doesn't come back. when it's warm outside it doesn't knock at all.

i use 87 octane gas and am currently running a mix of 10w30 and 10w40 havoline oil.

 

I usually go to Montezuma and Tiger Run. I would love to go to other places though. Where do you go to? Holla back as soon as possible.
Ill use octane 87 next time i fill up and see how it goes.

 

Could it be that i mixed 5w-30 oil with 10w-40 oil. I dont think it really matters does it?

 

"Could it be that i mixed 5w-30 oil with 10w-40 oil"

probably not. though my understanding is to not to mix different brands to prevent the differing additive packages from conflicting with one another.

 

Rathar than letting and engine idle for 5 minutes, you are better off to take it easy on the gas pedal for the first mile or 2. You will waste less gas that way and as long as you dont put it into gear and floor it, you will be OK.
All of the newer vehicle owner's manuals that I have read actually say that warm-up time isnt neccesary.
Cap'n

 

Yes your right. It does say that in most of the manuals for today's engines. That statement is made for people who are in a hurry and live in warm climates or there vehical is garge kept. It just tells you that you CAN start it and go without waiting. To bad they don't tell you under what circumstances that would not be a good idea. Like cold or damp weather or older vehicals with high milage.
I would love to see you jump in your Toyota after being parked outside all night at my place in WV in the middle of winter and it's (10 degrees out or much lower) and you start your vehical and take off in less than 10 seconds.
You may do it but it sure wont last you very long. Warming up cold steel is always a good idea no matter what your driving and the price of 5 minutes of gas at idle is nothing. Warming the fluids in your vehical before you make them work has never hurt a vehical that I know of.
This is just my openion after living in the cold East for many years and not ment to knock your openion at all so please don't take it that way Mike

 

My old '88 Camry would knock whenever I had forgotten to change to a heavier oil after the fridged portion of winter would pass.