Engine Knock

[FliteTime]

Hi All!

I bought a '99 GS 300 a year ago and just broke 100k miles. I'm worried about what I fear is a knocking under the hood. I have put both premium and regular gas in there, and the knocking goes down with premium, but it IS still there. I think the previous owner was putting regular in, too, that might have caused years of deposits to form. I know the car did get some kind of serious valve job right before I got it.

A mechanic recommend Amsoil P.I. to clean a stuck EGR valve might solve the problem. I hope it will be that easy. Do you think regular gas is an issue? Don't most cars recommend premium only to command a "premium" price and image?

The car also needs to go in for the 90k checkup. I feel like I'm on borrowed time without replacing the timing chain yet, and it bothers me every time I drive. The trouble is finding the time.

I'd appreciate your input. Thanks!

--c

[TurboGS300]

The GS needs premium! Try a couple cans of seafoam fuel injector cleaner over a few tanks of gas! You may have a bad knock sensor. <_<

[cruznroadking]

Need more info. Does the engine knock when idling or under acceleratiion or both?

If it just knocks when idling, possible valves out of adjustment. If if knocks only under acceleration then possible knock sensor. Also need more info on how extensive the valve work was.

There certainly are benefits to using 91 octane, including better performance & reduction deposits. If the 91 helped it's possible that there may be multiple knocking concerns

Regarding the timing belt, Lexus recommends 90k as a guide. Starting in ther late 90's they started using a heavier timing belt that lasts over 100k. My brother replaced his on a 91 LS with over 110k & is appeared to just started to get hairline cracks.

[mehullica]

Your car does not have an EGR valve. A bad knoch sensor will trun on the check engine light. I have seen a few bad cat converters make a knock type sound through the exhaust if you listen to the exhaust side of the motor. I have replaced a few blocks due to bad #6 cylinder wrist pins. Listen to the bottom of the motor with a long screwdriver on the lower oil pan and your ear, you'll hear a really loud knock from the bottom end. If that's the case you need a new block.

[SRK]

Your car does not have an EGR valve. A bad knoch sensor will trun on the check engine light. I have seen a few bad cat converters make a knock type sound through the exhaust if you listen to the exhaust side of the motor. I have replaced a few blocks due to bad #6 cylinder wrist pins. Listen to the bottom of the motor with a long screwdriver on the lower oil pan and your ear, you'll hear a really loud knock from the bottom end. If that's the case you need a new block.

←

I haven't heard of an engine for years now that doesn't have an EGR valve. It is a common method of reducing combustion temperature.

If you diagnosed a bad wrist pin, you must have removed the piston. Why not just re-bush the rod small end? Why replace the engine?

Sticking a screwdriver in your ear, hearing a really loud knock, and advising a customer they need a "new block"- that's diagnosis?

Are you just trying to scare FliteTime?

[TWINTURBO619]

Hi All!

I bought a '99 GS 300 a year ago and just broke 100k miles.  I'm worried about what I fear is a knocking under the hood.  I have put both premium and regular gas in there, and the knocking goes down with premium, but it IS still there.  I think the previous owner was putting regular in, too, that might have caused years of deposits to form.  I know the car did get some kind of serious valve job right before I got it.

A mechanic recommend Amsoil P.I. to clean a stuck EGR valve might solve the problem.  I hope it will be that easy.  Do you think regular gas is an issue?  Don't most cars recommend premium only to command a "premium" price and image?

The car also needs to go in for the 90k checkup. I feel like I'm on borrowed time without replacing the timing chain yet, and it bothers me every time I drive.  The trouble is finding the time.

I'd appreciate your input.  Thanks!

--c

←

Have you ever thought it just might be your valve springs need to be re-adjusted? You do have high mileage with your 99 GS. Or maybe the previous owner kinda didn't take care of her and let the oil run low and now your bearings on your crankshaft or worn out. Try looking into those.

[GuyTelefunken]

Your car does not have an EGR valve. A bad knoch sensor will trun on the check engine light. I have seen a few bad cat converters make a knock type sound through the exhaust if you listen to the exhaust side of the motor. I have replaced a few blocks due to bad #6 cylinder wrist pins. Listen to the bottom of the motor with a long screwdriver on the lower oil pan and your ear, you'll hear a really loud knock from the bottom end. If that's the case you need a new block.

←

I haven't heard of an engine for years now that doesn't have an EGR valve. It is a common method of reducing combustion temperature.

If you diagnosed a bad wrist pin, you must have removed the piston. Why not just re-bush the rod small end? Why replace the engine?

Sticking a screwdriver in your ear, hearing a really loud knock, and advising a customer they need a "new block"- that's diagnosis?

Are you just trying to scare FliteTime?

←

Just because you haven't heard of it, doesn't make it so. There is no EGR valve because it is not necessary. Internal recirculation in the cylinder head via correctly timed valve opening accomplishes the same effect. Many if not all engines with VVT or VVT-I (on the exhaust side) have no EGR valve. Even GM figured this one out with the I6 in the Trailblazer and lots of Cadillacs with the Northstar.

[mehullica]

I work for a Lexus dealer and know what a rod knock sounds like. Warranty makes us replace the short block, not just the wristpin.

[SRK]

I stand corrected gentlemen.

[VGR]

Sticking a screwdriver in your ear, hearing a really loud knock, and advising a customer they need a "new block"- that's diagnosis? Are you just trying to scare FliteTime?

←

Far from being a tire store or muffler shop mechanic, I think it's obvious mehullica has had state of the art Toyota training + hands on experience and that makes him a true Toyota guru.

On ebay I bought a 2001 Toyota Technician Engine Control Systems I Training Book and it validates what mehullica has been saying:

"VVT-i eliminates the need for an EGR valve. As a result of increasing the valve overlap in which the exhaust and intake valves are both open, the exhaust gas is able to flow to the intake side. Diluting the air/fuel mixture with exhaust gases reduces the combustion temperature and the production of NOx. Also, some of the unburned air/fuel mixture present in the exhaust gas will be burned."

[FliteTime]

Thanks for all the input!

I checked up on that valve job, turns out it was the 60k mile scheduled maintenance: a valve adjustment. I keep putting premium in there, and I think the noise is going away. Guess you can't get away with being cheap on a Lexus. I can hear the noise from outside only, like when I have the windows down. When I start the car, I can hear the noise bouncing off my other car. When driving past a high curb or pass parked cars, I can hear the noise then, too. With the windows up, I don't hear it.

I'll get some injector cleaner to help out. I heard a mechanic recommend Amsoil PI (Performance Improver), but even my local NAPA store doesn't carry it. It's selling for $7.70 at the Amsoil website. Do you guys have a recommendation, and isn't seafoam fuel injector cleaner made for marine engines only?

By the way, putting a screwdriver to your ear with the pointy-end against your valve cover IS a good way to listen for knocking over each cylinder.

[TurboGS300]

Seafoam is for ANY engine, it works great. <_<

[FliteTime]

ok, I'll look into it. Thanks!

[hughes369]

Your car does not have an EGR valve. A bad knoch sensor will trun on the check engine light. I have seen a few bad cat converters make a knock type sound through the exhaust if you listen to the exhaust side of the motor. I have replaced a few blocks due to bad #6 cylinder wrist pins. Listen to the bottom of the motor with a long screwdriver on the lower oil pan and your ear, you'll hear a really loud knock from the bottom end. If that's the case you need a new block.

I had my engine rebuilt in my 1994 GS300. I told the machine shop that i would assemble the engine. They forgot and i got the short block back and head rebuilt. I assembled the engine, did not check any clearances or check behind them, and ran it for about 500 miles on Castrol 30 weight oil, per their recommendation. During that time i had the upper radiator hose balloon like it was gonna explode. Also In that time span I hit a curb with the front crossmember kinda hard, i swerved to miss an idiot, and the heater hose got jarred loose from the heater valve which was already brittle and ready to break anyway so i didnt have a hose clamp on it. Of course all the coolant ran out that hose. I parked the car immediatly and plugged the heater hose thats off the back of the head and made it back to work, after i filled it up with coolant and water. Started noticing the engine vibrated at idle. Code 52 knock sensor code. So no power and plugged heater hose and retarded ignition timing. I made it home driving 60 miles at less than 2000 rpm. Replaced the upper hose, drained the coolant and filled it while car is inclinded on my car lift and replaced the heater valve. Put a bolt that was missing on the torque conveter back in, incase that was causing an imbalanced condition. Changed the oil to 5w-30 castrol also. Still have the code 52. I can idle the car all day long and the code wont come on until i rev it up a few times. The only problem i have fixed is the ballooning radiator hose, must have had a air bubble in the system to cause the expanding top hose. I verified that the head gasket was not blown by using the combustion gas analyzer kit from Lisle Tools that turns from blue to green if combustion gas is present in the radiator cap air space. Machine shop told me to change the front knock sensor and try disconnecting the torque converter to see if the trans is sending the vibration to the engine. Can i fix this without tearing down the whole engine again? Does the front knock sensor mean anything specific to one particular cylinder or area. If i take the engine out i want the least amount of teardown done as possible. Any advice is helpful. I have built many engines, but i was not planning on a redo this time, money is tight right now. Thanks.