My Siena is brand new and the engine knocks when cold and under load. I've had it back to the dealer several times and was told each time that the noise is "Normal." It wasn't until I spoke to a Toyota mechanic "Off the Record" that I received a real answer. I was told that the pistons on this engine do not have skirts, which was Toyota's attempt to increase fuel efficiency. The absense of piston skirts causes excessive piston slap until the engine heats up. I am still trying to verify this information. If anybody can help confirm or deny this information, it would be appreciated.
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Sorry but you have a bad piston rod bearing or main bearing ! You won't have any indicators lit on the dash as this is a engine mechanical fault ! EGR - Knock sensor has nothing to do with this ! Take it to a shop an they will tell you the same thing .
There is a possibility that the old motor was not burning properly and you have carbon build up on the O2 sensers. A poorly functioning O2 senser will not allow the Fuel/Air mixture to work as you give it gas under load. You could have multiple O2 sensers too.
A light knock at the top of the engine, or ticking, is the valve gear. This is not a worry if it eases when the engine is hot. A heavier knock down lower indicates trouble with the engine bearings, and this will usually get louder as the engine becomes hot. These problems have arisen in Camrys due to engine oil sludging. This starves the bearings of oil and they wear quickly. Toyota says it affects engines up to a 2001 build, but I have heard of 2002 engines being affected as well. Toyota insists it is due to owner neglect, but they have taken it on in limited circumstances:
A light rattling sound when the engine is under load indicates you should try a fuel with higher octane rating, although this would be unusual in your model unless you are using a fuel with high ethanol.
If you detected the engine knocking and the knock sensor also detected it to the extent it caused the ECM to set a diagnostic trouble code (DTC) then simply replacing the knock sensor was a waste of time and money, a case of shooting the messenger because you don't like the message. If the car is under warranty or guarantee then take it to the dealer for complete diagnostics. Do not under any circumstances be put off by lame explanations that they can't do anything. Take the car to other dealers to get written reports on the car. It is very important to get the reports in writing as this gives you legal protection with regard to the guarantee.
Yes it can. The knock sensor retards the timing due to irregular levels of octane in todays gasoline, to eliminate or reduce what is called a spark knock. A malfunction could cause your car to lose power when car is under a load or uphill due to pre detonation or constantly retarded spark to the engine. If not replaced it can cause engine damage or head gasket damage. Hope this helps.
Unusual for Toyota, have you checked your oil level? If it is a loud knocking, it could be a bad piston in the engine. Did you overheat the car at any point? The alloy head can warp easily if you get the engine too hot. Also check your coolant level to see if you are losing fluid. If the oil is white looking you have a serious issue with coolant mixing with the oil. Is it still under warranty for the powertrain, engine, transmission etc.?
The idle issue is normal. The idle is controlled by the ECU. There are no adjustments for the idle. Regarding the knocking noise, that could be several things, and I am hesitant to comment without hearing it. Take it to a Toyota Dealer & have a tech listen to it. We are very good at identifying noises on the service drive.