Engine rattling under heavy stress

It could be engine knocking. What type of gas do you use and what altitude do you normally drive at - NY - sea level?

 

A rattle is not normal and it could be from a loose timing chain. If you are willing to spend ~$700 or more to have it replaced, have a professional mechanic look at it.

Otherwise, just live with the noise. If the chain slips and the engine blows up, then take the car to a salvage yard, or have a used engine installed.

Make sure you are not confusing this with an engine knock, as previously suggested. You can try 91 octane fuel to see if there is any change, if you are uncertain about what a knock sounds like.

 

I wouldn't have thought 1000-2000 ft would be a problem. However, you could try gas that is the next grade up and see if that makes a difference.

It sounds like this is not a new thing from the way you worded the original post, if it is engine knocking (or pinking as it is also known), you do want to stop it as it can damage your engine. Use higher octane fuel until the engine no longer pinks. If using higher octane fuel makes no difference, then it might be something else.

A good mechanic or friend who knows what engine knock sounds like could go for a drive with you and confirm the sound.

hope this helps.

 

Could be loose valves

 

The timing chain replacement in principle is similar to a timing belt replacement. If you have experience doing timing belts then you could reasonably do the Prius timing chain.

It is necessary to remove the cowl that runs across the firewall. Then you will need to remove the engine valve cover, engine front cover (which contains the engine oil pump) and crankshaft pulley for access to the timing chain. The engine mounting bracket near the passenger side fender has to be removed so you need a hydraulic floor jack to hold the engine up. Of course there are many other parts that have to be removed as part of the process, like the engine coolant pump which is mounted to the engine front cover, the four spark igniters mounted to the engine valve cover, etc.

I suggest you obtain the procedure from techinfo.toyota.com since there are many little details that you need to be aware of, like how to lock the plunger that provides pressure on the chain tensioner.

 

If you are going to check the chain, check the valves too. You need to remove the chain in order to adjust the valves

 

While you have the engine valve cover off, you can check the valve clearances. If you should find that the clearances need adjusting, it is necessary to remove the camshafts and replace the spacers for the valves that need adjustment. This is not a trivial effort and should be avoided if possible.

 

The engine has a knock sensor, and the computer is supposed to automatically fine tune the ignition timing whenever knocking is detected so that it goes away. If the engine is in fact routinely knocking and you are able to make a difference by changing the fuel octane, there could be something wrong with the knock sensor. The service manual may provide steps for testing it.

If there's something wrong with the knock sensor circuit, that's what you would want to fix, so you don't need to try to work around it by buying different fuel.

-Chap

 

I agree, try 91 octane fuel and if it helps, it could be a bad knock sensor.

 

An engine knock is the same as spark pre-ignition. Under normal operating conditions, the spark plug ignites the fuel/air mixture in the cylinder prior to the piston reaching top dead center. Usually the spark timing is advanced a few degrees before top dead center under the assumption that it takes some time for the mixture to explode and exert force on the piston. As the engine RPM increases, the amount of advanced timing in degrees also increases.

An engine knock occurs because the fuel/air mixture ignites sooner than it should. In extreme cases this can cause mechanical damage to the engine.

Most gasoline engines including the Prius engine, have knock sensors which detect the presence of an engine knock and provide a sensor signal to the engine ECU. The engine ECU will then retard ignition timing so that the knock is diminished.

If you want, you can try replacing the knock sensor. However if the knock is minor at 87 octane, I would not bother.

One reason that a high mileage engine may develop an engine knock over time is that carbon from combustion byproducts builds up in the cylinders and on the pistons. This increases the effective compression ratio of the engine (because there is slightly less volume in the combustion chamber due to the carbon coating when the piston reaches top dead center), and therefore, a higher octane fuel is needed for the engine to run smoothly.

A higher octane gasoline has additives which reduce the tendency of the gasoline to ignite. This is why, when you moved to a premium grade of gasoline, the knock went away.

So now that you have determined that the noise is due to an engine knock, you can experiment with a lower grade of gasoline, like 89 octane, to see if that is sufficient.

You may also find that some 87 octane fuel is better than others with regards to suppressing the knock. For example when I was living in southern CA, I noticed a low level knock with one of my Prius. It was not bad enough for me to be concerned about that issue.

Now that I live in AZ, there is no issue with engine knock. I assume that part of the problem was the CA-formulated gasoline.

 

My Prius 08 110,000 miles when I drove on the hill or speed on freeway have the pinging or knocking sound.
I step out from the gas and the sound gone. Every time have problem like this I did that.
I don't know why I try to do many thing like Patrick recommend as
-Use premium grade gas
-Change spark plugs
-Change Air filter
-Clean the MAF sensor
-Put Seafoam to clean the injection
Yesterday I change the oil I found my use oil left only 2 qtrs. It's engine burn out of oil.
But I wonder the engine still have a lot of power I don't think the engine worn out.
Please help me to analysis the problem from and How to solve the problem. Thanks

 

1. You really need to develop the habit of checking engine oil level regularly, and not allowing the oil level to drop below the lower dimple on the dipstick - unless you are interested in replacing the engine sooner than otherwise might be necessary.
2. Are any warning lights on?
3. Did you install the correct NGK or Denso iridium spark plugs, or some lesser substitute?
4. What gasoline brand are you buying? Have you tried Chevron 91 octane premium fuel?

 

I use Gumout Regane every three fill ups, and works great in better gas mileage as well as silencing ping.

I do not know if this is still recommended however.

Probably better just using high octane every three fill ups instead.

 

It no warning light on,
I try to use gasoline many brand still have same problem.
I changed spark plugs use NGK but now I changed back to OEM
Where the oil go? I checked the engine no leak at all.
Do you think they go to exhaust?
Someone recommend to change PCV Value. What do you think?