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  #1  
Old 03-29-2003, 09:54 PM
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SL 600 pinging/knock

Notice pinging/knock on slow steep uphill curves on accelerating out. Always use premium gas. Dont these cars have knock sensors?. 93 model with 35000 miles.
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  #2  
Old 03-30-2003, 12:56 AM
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knock sensor, is really NOx meaning Nitrous oxide emissions, is what that means, that senses that the car isnt running good...They could be pluged up, but if your car knocks, its not running properly, and with 600s it can be a lot of things, they are picky cars. Ill ask my friend, he loves to work on 600s.

EDIT: I AM IN ERROR PLEASE IGNORE THIS POST
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Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.

Last edited by omegabenz; 03-31-2003 at 05:02 PM.
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  #3  
Old 03-30-2003, 06:03 AM
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Hey omegabenz, where in the world did you hear that!!! Knock sensors and oxides of nitrogen(NOx) have absolutely NOTHING to do with one another. I'd suggest checking your information for accuracy before posting. NOx is an exhaust emission that is controlled by cooling the combustion temperature, usually by the introduction of exhaust gas(EGR). Knock sensors are simply piezo-type vibration sensors mounted to the engine block. Knock sensors can't get "plugged up". Pinging/knocking results from uncontrolled burn of the fuel/air charge. The engine noise that results is the sound of the pistons slapping the cylinder wall. This causes a vibration that's picked up by the knock sensors. The engine/ignition control unit retards the timing until the knocking stops. There are also several other reasons for pinging/knocking. Lean fuel mixture, excessive load, high engine temp and fuel quality can all cause this. Either way, it needs to be taken care of. Phelan, make sure that your transmission is in the correct gear when climbing those "slow, steep hills". If necessary, manually shift to a lower gear, though the transmission should do that automatically. Good luck
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Old 03-30-2003, 11:31 AM
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Quote:
Originally posted by omegabenz
knock sensor, is really NOx meaning Nitrous oxide emissions, is what that means, that senses that the car isnt running good...They could be pluged up, but if your car knocks, its not running properly, and with 600s it can be a lot of things, they are picky cars. Ill ask my friend, he loves to work on 600s.
omegabenz...........

You may want to consider taking Electronic Engine Controls 101 !!!
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Old 03-30-2003, 12:12 PM
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your comment is accepted,...but please be nice and stay cool.
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  #6  
Old 03-30-2003, 12:33 PM
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ILUVMILS: Gonna give a bibliography on that??
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  #7  
Old 03-30-2003, 02:12 PM
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knock sensor, is really NOx meaning Nitrous oxide emissions, is what that means, that senses that the car isnt running good...They could be pluged up, but if your car knocks, its not running properly, and with 600s it can be a lot of things, they are picky cars. Ill ask my friend, he loves to work on 600s.

None of that is wrong. People pronounce NOx (knock) sensor. If the car is pinging its not running right, I said that.

Nothing I said was wrong.

EDIT: IGNORE THIS POST
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No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.

Last edited by omegabenz; 03-31-2003 at 05:03 PM.
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  #8  
Old 03-30-2003, 02:51 PM
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Austin, I will kindly agree with the others. A knock sensor is not an emissions sensor. Pinging literally sounds like a ping inside your motor. The "real" word for it is predetonation. This is when your mixture detonates before the spark hits. Check out this website So the knock sensor literally "hears" the knock inside the motor and adjusts the timing so it detonates on time. So the different octanes of gasoline have different detonation points that correpond with the optimal detonation point designed into the motor. So when it is predetonating, and the timing is adjusted, it is not at its optimal point, so your motor is not running at peak efficiency. Maybe we need stevebfl, MBDOC or gilly to explain this.
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  #9  
Old 03-30-2003, 02:58 PM
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"...The piston can overheat and knocking can and will occur. This knocking is caused by ignition of the gas/air mix in your cylinder before the spark of the spark plug. This causes temperature and pressure peaks that will melt your piston, crack your cylinder head, and drop one of your exhaust valves. You have heard about those abrupt deaths of air cooled engines..."

*EDIT: THE KNOCK SENSOR DOES NOT DO THIS, but what I have said about this Chemistry stuff is true. The EGR valve lowers the temperatures inside the combustion chainber so that the NOx emissions are reduced.

See the NOx sensor picks up knocking because the cylinder walls and piston get really hot because of the lean fuel mixture which makes the bonds of N2 which is regularly found in air at close to 80% of air to combine with O2 to for N20, NO, N2O5, and other NOx mixtures. Instead of N2 being a non reacting molecule passing through the engine, it reacts with air at high temperatures to form N20, NO, N2O5, etc. Basically N2 + O2 ~~~> NOx emissions, which is an endothermic reaction (requires heat to go).


http://www.mbusa.com/brand/container.jsp?/overview/overview_engine.jsp?spec=2&subNav=overview&yearModelCode=88_SL600CR&class=88_SL&rnav=012345678&menu=2_3

SL600 1993 has 11:1 pistons, geez...make sure you run 92, 94, 98 octane gas...maybe you got a slug of bad gas.

But lets get to the real problem. The SL600 isn't running properly, if it knocks, like pinging noises, its running too lean.
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No Benzes in the stable at the moment, but itching for one again.

Former Mercedes in the Stable:
1983 300CD Turbo diesel 515k mi sold
1984 300CD Turbo Diesel 150 k mi sold
1982 300D Turbo Diesel 225 sold
1987 300D Turbo Diesel 255k mi sold
1988 300 CE AMG Hammer 15k mi sold
1986 300E Amg Hammer 88k mi sold
1992 500E 156k mi sold
etc.

Last edited by omegabenz; 03-31-2003 at 05:06 PM.
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  #10  
Old 03-30-2003, 03:42 PM
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I concede that I could be wrong. I give up on this one...because the discussion is getting beyond my knowlegde. If I'm not wrong, along with ILUVMILS and manny....then I think we need a seasoned tech (steve, etc.) to settle this one. I think we need one of those guys to settle this one way or the other! Have a good day.
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  #11  
Old 03-30-2003, 05:20 PM
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Fellows, I just wanted to get an idea re the etiology of the pinging. I know all about poor gas, timing etc. What is likely to be wrong with this engine and how do I approach the issue.
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  #12  
Old 03-30-2003, 05:34 PM
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Alldata knock sensor article

Description and Operation

PURPOSE
The knock control system allows calibration of the ignition timing for normal operating conditions, while eliminating the danger of knock or detonation due to influences by heat, load, fuel quality or engine deposits.

LOCATION
The knock sensors (A29 and A30) are located on the center of engine block between the cylinder heads.

CONSTRUCTION
The knock sensor (C) consists of a housing (3) a piezoelectric crystal (4) mounted on a threaded sleeve (5) between two connector strips (6). One side of the assembly is fitted with a damping weight (7) and spring washer (8) secured by a nut (9).

OPERATION
The four knock sensors (two A29 and two A30) are subjected to vibrations generated by knock. The vibrations cause a small distortion on the surface of the piezoelectric crystals, which consequently generates a small voltage. This voltage is read by the EZL/AKR control module. The control module retards the ignition point for an individual cylinder by 3°crankshaft angle per ignition cycle (Max. of 12°). The knock control system develops its maximum ignition retard of 12°crankshaft angle at a coolant temperature of 194°F.
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  #13  
Old 03-30-2003, 05:36 PM
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Alldata knock sensor article

One more picture:
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  #14  
Old 03-30-2003, 09:33 PM
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What octane of premium do you use? Anything greater than or equal to 91 can be called premium. I avoid running anything below 92 in my Talon as it is very sensitive to knock (93+ normally). First things first, try increasing the octane level of your fuel. This predetonation can cause catastrophic failure, if it starts pinging let off of the accelerator before you damage the motor.

What I wonder (as I do not know anything about SL600s) is why isn't the knock sensor picking this sound up, telling the computer, and retarding the spark? Even if the fuel mixture is running lean or whatever could be causing the knock, the car should see the problem and adjust the timing so nothing is damaged.
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  #15  
Old 03-30-2003, 09:40 PM
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Omegabenz, there is NO SUCH THING as a NOx sensor. There is, however, a KNOCK sensor. I believe myarmar's post will corroborate the information in my previous post. I consider myself a "seasoned tech" (14 years with MB, and counting ) so I'm not making this up. The information in your original post is inaccurate, and I felt obligated to correct you. Sorry. The Forum members expect to hear OPINIONS, but sometimes only the FACTS will do. Have a nice day.
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