high rpm rattle noise
07-04-2008, 11:17 PM
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high rpm rattle noise
i have a 1999 f150 4x4 4.6l and when i am crusing engine sounds fine i start giving the engine load you start to here a light rattling.. sounds like it is comin from the trans tunnel. when i get wot and higher in the rpm the rattle gets distinct and load but the engine pulls strong!
could this be something wrong or worn in the tranny?
i have been told it might be catalytics?
engine at low rpm and idle sounds great!
i am puzzled, any ideas?
could this be something wrong or worn in the tranny?
i have been told it might be catalytics?
engine at low rpm and idle sounds great!
i am puzzled, any ideas?
07-05-2008, 09:02 PM
#2
crush a little car today
From what you say it sounds like spark knock. I wouldn't be trying to reproduce it with loading the engine repeatedly and hurting something. It could be something loose so check the area you hear it from.
07-06-2008, 02:28 AM
#3
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That is your engine knocking! Just for kicks if you can afford it...LOL...run your tank pretty empty & put several gallons of Premium in...run it a while to flush out the 87 then try it again. Probably will go away if it is engine knocking.
When I tow my trailer I use Premium to preven this as I am really into the throttle a lot & loading the engine.
When I tow my trailer I use Premium to preven this as I am really into the throttle a lot & loading the engine.
07-27-2008, 01:00 AM
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i get sometin like that besides the exhaust tickish noise. it almost sounds like valves going crazy at high rpms . some times i think im a hypercondreac and think. but could be in the dash? i hear it though
12-25-2009, 03:06 AM
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high rpm engine rattle
I get the exact same thing on my '98 4.6 triton. It sounds like someone is shaking a can of spray paint but only under load. I can't hear the sound when its in park and I rev the motor, but when I get it up to about 2500 RPMs in drive, its is clear as day. My truck has 165k miles and was well maintained. I've also been told it might be the cats. I also checked the idler pulleys, but it all checked out fine. 
If you find out what it is, let me know and if I find out first I'll reply to the thread. Best of luck.
If you find out what it is, let me know and if I find out first I'll reply to the thread. Best of luck.
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12-25-2009, 04:17 AM
#8
sorta sounding like a spark knock...have any CEL lights on??
12-26-2009, 01:59 AM
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No CEL. How do I check for spark knock, and will I hurt the motor if i let it go much longer? I also changed the plugs with Motorcraft platinum plugs and it still does it.
12-26-2009, 05:33 AM
#10
crush a little car today
Spark knock can eventually lead to the destruction of a motor. What it is is the sound of multiple flame fronts colliding in the cylinder. Normally when the air/fuel mix is ignited by the spark plug one flame front propagates in a controlled burn across the top of the piston causing the expanding gases to drive down the piston. This also causes a gradual rise in pressure. When spark knock occurs there is an instantanious pressure spike and a hammering effect on the soft aluminum alloy of the piston. The weakest point will start to crack then the piston will eventually destroy itself.
Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading.
Mild or occasional detonation can occur in almost any engine and usually causes no harm. But prolonged or heavy detonation can be very damaging. So if you hear knocking or pinging when accelerating or lugging your engine, you probably have a detonation problem.
CAUSES OF SPARK KNOCK
The things that usually cause spark knock (detonation) are:
(1) The EGR valve that is not working. The EGR
is supposed to open when the engine is accelerating or lugging under a load. This allows intake vacuum to suck some exhaust in through the EGR valve to dilute the air/fuel mixture slightly. This lowers combustion temperatures and prevents knock. Inspect the operation of the EGR valve, and check for a buildup of carbon deposits on the valve pintle or valve port that may be blocking the flow of exhaust back into the engine. Clean off the carbon deposits with a wire brush and carburetor cleaner, or replace the EGR valve if it is defective.
(2) A bad knock sensor. Your engine has a knock sensor that should detect detonation and tell the computer to retard the ignition timing. If your engine requires premium grade fuel, but you are using regular or mid-grade fuel, the knock sensor should detect any detonation that may occur when the engine is working hard under a load and cause the PCM to retard timing. This reduces power a bit but protects your engine against detonation. However, if the knock sensor is not working, spark timing will not retard when it should. Consequently, you may hear a pinging or rattling sound (spark knock) when accelerating, driving up a hill, or when the engine is lugging under a heavy load.
The knock sensor can be tested by tapping on the engine near the sensor (not the sensor itself) with a wrench while watching spark timing and/or knock sensor input on a scan tool to see if it sends a timing retard signal.
NOTE: Overadvanted ignition timing can also cause the same thing (spark knock). But on most late ignition timing is not adjustable and is controlled by the engine computer. The only way to change the timing advance would be to flash reprogram the PCM.
(3) Excessive carbon buildup in the combustion chambers and on the tops of the pistons. This is usually more of an issue with older, high mileage engines or vehicles that are only driven for short trips and never fully warm up. Treating the engine with a dose of top cleaner or a fuel system additive that also removes carbon from the combustion chamber can usually clears this up. Some repair shops use a machine called a MotorVac to perform an engine carbon cleaning procedure. The machine uses a concentrated detergent to flush out the fuel injection system and combustion chambers.
(4) Compression ratio too high. If an engine has been rebuilt and the cylinders have been bored to oversize, it will increase the engine's static compression ratio. Or, if the cylinder head has been resurfaced to restore flatness, this will reduce the volume of the combustion chamber and also increase the engine's static compression ratio. These changes will increase engine power, but also the risk of detonation on regular 87 octane fuel. Such modifications may require using higher octane 89 or 93 octane premium fuel and/or retarding spark timing. Engines that are supercharged or turbocharged are also at much higher risk of detonation because the forced increases compression. This usually requires using premium fuel.
(5) Cheap gas. Regular grade gasoline is supposed to have an octane rating of 87. If the or their refiner is cutting corners and the fuel is not 87, it may knock. The fix for this is to try a tank of mid-range or premium gasoline. Be warned, though, that some stations cheat on this too, and don't always give you the octane rating claimed on the pump. Premium costs more, but may be required to reduce the knocking. Or, if you always buy gas at the same gas station, try a different gas station. Don't buy the cheapest gas you can find. BP, Shell and Mobil are all good brands.
(6) Engine overheating. If the engine is running too hot because of low coolant, a cooling fan that isn't working, a plugged radiator, bad water pump, sticking thermostat, etc., it may cause the fuel to detonate.
Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading.
Mild or occasional detonation can occur in almost any engine and usually causes no harm. But prolonged or heavy detonation can be very damaging. So if you hear knocking or pinging when accelerating or lugging your engine, you probably have a detonation problem.
CAUSES OF SPARK KNOCK
The things that usually cause spark knock (detonation) are:
(1) The EGR valve that is not working. The EGR
is supposed to open when the engine is accelerating or lugging under a load. This allows intake vacuum to suck some exhaust in through the EGR valve to dilute the air/fuel mixture slightly. This lowers combustion temperatures and prevents knock. Inspect the operation of the EGR valve, and check for a buildup of carbon deposits on the valve pintle or valve port that may be blocking the flow of exhaust back into the engine. Clean off the carbon deposits with a wire brush and carburetor cleaner, or replace the EGR valve if it is defective.
(2) A bad knock sensor. Your engine has a knock sensor that should detect detonation and tell the computer to retard the ignition timing. If your engine requires premium grade fuel, but you are using regular or mid-grade fuel, the knock sensor should detect any detonation that may occur when the engine is working hard under a load and cause the PCM to retard timing. This reduces power a bit but protects your engine against detonation. However, if the knock sensor is not working, spark timing will not retard when it should. Consequently, you may hear a pinging or rattling sound (spark knock) when accelerating, driving up a hill, or when the engine is lugging under a heavy load.
The knock sensor can be tested by tapping on the engine near the sensor (not the sensor itself) with a wrench while watching spark timing and/or knock sensor input on a scan tool to see if it sends a timing retard signal.
NOTE: Overadvanted ignition timing can also cause the same thing (spark knock). But on most late ignition timing is not adjustable and is controlled by the engine computer. The only way to change the timing advance would be to flash reprogram the PCM.
(3) Excessive carbon buildup in the combustion chambers and on the tops of the pistons. This is usually more of an issue with older, high mileage engines or vehicles that are only driven for short trips and never fully warm up. Treating the engine with a dose of top cleaner or a fuel system additive that also removes carbon from the combustion chamber can usually clears this up. Some repair shops use a machine called a MotorVac to perform an engine carbon cleaning procedure. The machine uses a concentrated detergent to flush out the fuel injection system and combustion chambers.
(4) Compression ratio too high. If an engine has been rebuilt and the cylinders have been bored to oversize, it will increase the engine's static compression ratio. Or, if the cylinder head has been resurfaced to restore flatness, this will reduce the volume of the combustion chamber and also increase the engine's static compression ratio. These changes will increase engine power, but also the risk of detonation on regular 87 octane fuel. Such modifications may require using higher octane 89 or 93 octane premium fuel and/or retarding spark timing. Engines that are supercharged or turbocharged are also at much higher risk of detonation because the forced increases compression. This usually requires using premium fuel.
(5) Cheap gas. Regular grade gasoline is supposed to have an octane rating of 87. If the or their refiner is cutting corners and the fuel is not 87, it may knock. The fix for this is to try a tank of mid-range or premium gasoline. Be warned, though, that some stations cheat on this too, and don't always give you the octane rating claimed on the pump. Premium costs more, but may be required to reduce the knocking. Or, if you always buy gas at the same gas station, try a different gas station. Don't buy the cheapest gas you can find. BP, Shell and Mobil are all good brands.
(6) Engine overheating. If the engine is running too hot because of low coolant, a cooling fan that isn't working, a plugged radiator, bad water pump, sticking thermostat, etc., it may cause the fuel to detonate.
Last edited by kaboom10; 12-26-2009 at 05:40 AM. Reason: info correction
