Valves tapping Avalon 2000 90,000 miles

How do you know the valves are tapping?

Sounds like maybe a minor case of pinging, if it only happens under load. Grab a can of BG44k at your parts store or visit a shop for a carbon depletion service. It's not unreasonable at all to expect a little carbon buildup at 90k miles.

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Doesn't the Avalon require premium gas? (What does the manual say?)

...

I had a 1998 Avalon, same motor as the 2000, I think,...and I used regular. The manual states that for superior preformance use a higher grade (which I feel is balony), but regular was satisfactory. Of course all 'regular' gas is not the same...some stations handle a little better octane rating than others and you could get pre-detonation. Try a mid grade gasoline and see if the clatter goes away. Roll down your window and listen when the engine is under a slight load.

...Allen

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I highly doubt switching to a higher octane will fix anything. It's a non interference engine, why would the valves ping? Try running some seafoam through a vacuum line at the TB and look for an exhaust leak. Beware that seafoam will smoke all your neighbors out, so do it when nobody is around and 30 minutes of billowing smoke wont bother anyone. I have a suspicion that you have a leak at your exhaust manifold, the leak 'pings' against the heat shield and sounds like a valve tapping. If the more you run the car the less you hear the ping, chances are its a leak, the heat expands the metal and seals the leak.

What ARE you talking about son?...

Eh?...pre-detonation?...what's that?...gee...

Was I not clear?

Why didn't you just answer the original question instead of throwing around your un-helpful garbage.

...Allen

Well, I suppose it's all according to what your subject is...you don't seem to be talking about automobile engines here...at least not internal combustion reciprocating ones that we're all familiar with. So you might indeed be clear, who knows?

Unhelpful?...golly, I was just trying to fimd out what pre-detonation was...you were giving out advice so I thought that perhaps you were an expert.

Obviously you're the one who has little clue about what we are talking about here. I was pretty clear I think on figuring out what the subjects problem was. You are saying im not talking about engines yet you don't know what detonation is, come on.

No no Josh!...I know perfectly well what detonation is...it's your 'pre-detonation' that I've never heard of!... And this:

What does this have to do with anything?

See now why I don't know what you're talking about?... :)

I never said pre-detonation, somebody else did and I've heard many people say PRE-detonation also. I also know damn well you knew what he meant and you were just being cocky about it.

You're right since he's not complaining about a major engine problem it has nothing to do with it. It's probably an exhaust leak, or at worst oil starvation, so I'm betting on the leak.

"Josh" wrote: snip

Sorry, yes you're right, it was someone else who said 'pre-detonation'...but you -did- say:-

Now, what in hell would that sentence mean?, that if it -were- an interference engine then the valves might 'ping'?...(whatever the hell that means). You certainly aren't describing any kind of an engine that -I- know about...

If your reading and auditing this forum for education purposes (which it appears), and if I were a professor, I would say stop talking in class and you might learn something. So far, you have contributed nothing to this thread except criticism about what others post, and your seeming lack of understanding certain terms. If you have nothing valid to contribute, why make your pitiful efforts at pretending some kind of intellegence of these subjects that you have shown you know nothing about...in other words, sit quietly or leave the class, it may be a little bit too advanced for you in certain fields.

...Allen

"Allen L." wrote: snip

Just bothers me when people pass out garbage and others gobble it up as if it were good data and others (like you) defend it. Is it that you don't know the difference between good data and bad? I objected to his

and you let that pass as if it were good info and give me a hard time for objecting to it....what does that say about -your- understanding of internal combustion engines?. I think it's you who needs to pay attention in class sonny.

You just made my point for me...why in the hell don't you explain what he means by "It's a non interference engine, why would the valves ping?" as you

...Allen

Allen,

An interference engine is one where the valves would come in contact with the piston if the valve timing was not synchronized with the crankshaft timing. The valve-crank timing would get out of synch if the timing belt or timing chain, as the case may be, breaks. If the valves strike the pistons, then major engine damage will occur, usually necessitating new valves and/or pistons, and the engine will not run at all.

A non-interference engine is one where the valves cannot touch the pistons, even when the piston is in top-dead-center position and the valves are fully opened.

Interference engines tend to be slightly more efficient than non-interference engines but non-interference engines are more forgiving if the consumer does not get the timing belt changed according to the manufacturer's recommendations.

Whether an engine is an interference or no-interference type has no relation to the valve tapping/pinging/knocking noise the OP complained of.

Most likely, the "valve tapping" noise the OP mentioned when the engine is under a load is what is commonly referred to as pinging. The noise is caused because the air/fuel mixture in the combustion chamber is detonating prior to the spark plug firing. Someone incorrectly referred to this condition as "pre-detonation." When you compress the air/fuel mixture, heat is created and if you compress it enough, it will eventually detonate. The octane in the gas raises the amount of compression necessary to detonate the fuel.

Some people have mentioned using a higher octane fuel to prevent the pinging but the Avalon has a knock sensor and electronic spark advance to prevent the condition from occurring. The knock sensor is a piezo-electric crystal like what you see in barbeque sparkers and some lighters. When the crystal is compressed, either from twisting or striking the crystal, the molecules create a static spark. The knocking in the engine compresses the crystal, which creates a spark. The knock sensor is wired to the car's electronic control unit so the spark travels through the wires to the ECU. When the ECU senses several sparks coming from the knock sensor, it will retard the spark timing. The engine shouldn't ping for more than 3 seconds before the ECU retards the spark timing. If the engine continues to ping, I'd check the wiring between the knock sensor and ECU and the knock sensor itself. The ECU wouldn't detect a lack of signal from the knock sensor so it may not set a check engine light.