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Discussion Starter #1
I could really use some help with this one. I own a 93 500sl with ~84,000 miles. Last summer and this spring I have noticed a very slight missing that occurs is noticiable at any constant engine RPM or road speed. The missing is very short lived, just feels like a little tug backwards. Most of the time it doesn't even show up on the tach - other times I believe I can catch a fleeting every so slight dip in RPMs. It can occur when the car is hot or when cold. It can occur when the weather is hot or cold. It can occur if the gas tank is full or near empty. It can occur if the car is idling or moving at 90mph. It can occur some days and not at all on other days. It can occur every few seconds or every few minutes. The only things I can tell is that when it occurs, the engine speed is steady (never notice anything during accelration) , and when it occurs it appears the missing seems to be consistent in time from miss to miss although that miss interval may be different different days. Any ideas? If it had any dependence on RPM, temp, car speed, gear, tank level, etc it would be easier to diagnose. Seems to irregular to be fuel filter, injector, fuel tank pressure, fule distributor, etc....... I worry about impending failure of some component but don't have an idea of where to start.

Thanks,

Todd
 

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Administrator
1998 Pano SL500; 1993 SL500; 2005 ML270cdi
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I had this a few months ago! A plug change and a MAF clean cured the problem.
 

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Discussion Starter #3
RedLiner - My plugs are only 2 years old <20,000 miles but I can give that a try. What is a MAF clean?

Thanks,

Todd
 

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00 SL500 SOLD, 05 SL600 Sport, 09 Silverado 4x4 LTZ,SOLD '15Silverado LTZ 6.2 8Speed John Deere 318
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Try plugs first, Plug wires next, Injector cleaner next, Distributor caps &rotors next, If none of the above corrects the problem, PUNT!!!!!!!! {take it to an EXPERT}
 

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1998 Pano SL500; 1993 SL500; 2005 ML270cdi
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RedLiner - My plugs are only 2 years old <20,000 miles but I can give that a try. What is a MAF clean?

Thanks,

Todd
If the plugs are 20,000 miles definitely change them. If you don't know what a MAF (Mass Air Flow) sensor is, please try searching for MAF on this forum. There are many topics on MAFs and how to clean them.
 

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Greek God of the R129
SL500-500SEL-190E
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8,372 Posts
RedLiner - My plugs are only 2 years old <20,000 miles but I can give that a try. What is a MAF clean?

Thanks,

Todd
Lol.
Only, 20,000 miles on plugs, rotors etc is a very long time.
Unless you are looking for trouble.
Think for a moment how many times they spark in one minute.
Regards.
aam.
 

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Discussion Starter #7
Thanks for the thoughts - sorry for the delay. This has been a busy week, son home from college, daughter graduating from high school, grad party, etc. Will try to get some time in on fixing it this weekend. Yes, I am familiar with the mass air flow sensor, just wanted to confirm in this world of acronyms. Its the rythmic intermittent nature that just gets me. WHat ever happened to the wires/ plugs, etc that were supposed to go 100000 miles;)
 

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Greek God of the R129
SL500-500SEL-190E
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8,372 Posts
Thanks for the thoughts - sorry for the delay. This has been a busy week, son home from college, daughter graduating from high school, grad party, etc. Will try to get some time in on fixing it this weekend. Yes, I am familiar with the mass air flow sensor, just wanted to confirm in this world of acronyms. Its the rythmic intermittent nature that just gets me. WHat ever happened to the wires/ plugs, etc that were supposed to go 100000 miles;)

Ehehe.
100,000 miles.
Ask Jesus for miracles, that is not my department. ;)
Regards.
aam.
 

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MB SL600, MB 380SE, Suzuki Grand Vitara, 38' Chris-Craft, Volvo V70XC, and my own two feet...
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+1 on this 100k mile spark plug nonsense. I've had a variety of cars, and every single one ran better when I changed the plugs out every year or maybe 18 months, depending on how often I drove the vehicle.

I think, as car enthusiasts, we're operating on a different level vs. the spark plug manufacturers who claim 100k miles. We don't want it to just work, we want it to perform well.

Will a plug still work period after 100k mi? Most likely.

But will it work well? Probably not.

And will it work as good as it did when it was new? Absolutely not.

Anytime you have an electrical gizmo that is constantly exposed to that much heat, carbon, gunk, etc., it's going to wind up being a throw-away item that needs replacement pretty often.
 

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Greek God of the R129
SL500-500SEL-190E
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They do run the tests in a control environment so the miles predicted on the parts are high.
In real life it is a different story.
Below zero temperatures and other factors, the life expectancy gets much less.

As the spark gap gets larger the possibility of burning the ignition coils and other parts is higher.
But they are not going to tell you that.

Regards.
aam.
 
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