SL/R129: Check Engine light
Thread Starter
Junior Member
Joined: Aug 2013
Posts: 40
Likes: 1
From: Linn County MO
SL500
Check Engine light
My check engine light is on and nothing seems wrong. Are there any self diagnostics I can do to find the fault?? It's a 99 SL500.
Last edited by rscruggs2; Mar 30, 2015 at 07:46 PM.
Member
Joined: Jul 2013
Posts: 126
Likes: 5
From: Saint Augustine, FL
1998 SL500
Or buy a code reader and read them yourself (and reset the MIL which the FLAPS may not be willing to do). They are not that expensive (Harbor Freight has models starting at $50).
The readers I had were all 10 to 20 years old, so last Fall I bought this very capable HF unit on sale for $90--with a $20 coupon = $70.
Once you have the codes post 'em here or "google" them for more info/suggestions...
Thread Starter
Junior Member
Joined: Aug 2013
Posts: 40
Likes: 1
From: Linn County MO
SL500
Senior Member
Joined: Aug 2006
Posts: 391
Likes: 6
From: So California
2000 SL500
Yes, and I think you have just applied a band aid and it will now take a couple of weeks for the DTC's to show up again and the CEL to come back on. If it does may I suggest that you pay your local Indy to print out the codes from a MB SDS since you also have a 32 PIN connector located on the passanger side back by the firewall that allows a Tech to read any/all DTC's that the car may throw. Cost is free or about $50-$75 pending your relationship..
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Thread Starter
Junior Member
Joined: Aug 2013
Posts: 40
Likes: 1
From: Linn County MO
SL500
Diagnostics complete. The connector on my car is on the drivers side by right calf and up. It said I had a loose gas cap and 3 plugs that had missed. That's easy to understand as they are the original plugs that came with the car. I ordered 16 plugs from AH and will get them installed when my mechanic (friend of mine) is free. The check engine light is out by the way. I checked my mileage today and it was 23.5MPG so things can't be too bad!
Last edited by rscruggs2; May 4, 2015 at 06:30 PM.
Member
Joined: Jul 2013
Posts: 126
Likes: 5
From: Saint Augustine, FL
1998 SL500
The misfire codes are not thrown only because of bad plugs, they can also be triggered by fuel injection or engine mechanical problems--though if you are still running the OEM plugs that would be a distinct possibility.
How many miles on them?
Here is the functional description of the misfire detection system...
How many miles on them?
Here is the functional description of the misfire detection system...
Thread Starter
Junior Member
Joined: Aug 2013
Posts: 40
Likes: 1
From: Linn County MO
SL500
The misfire codes are not thrown only because of bad plugs, they can also be triggered by fuel injection or engine mechanical problems--though if you are still running the OEM plugs that would be a distinct possibility.
How many miles on them?
Here is the functional description of the misfire detection system...
How many miles on them?
Here is the functional description of the misfire detection system...
Member
Joined: Jul 2013
Posts: 126
Likes: 5
From: Saint Augustine, FL
1998 SL500
At two 1.2 miles a day trips for 12 years that engine never got hot enough to boil off the crap byproducts of combustion, the plugs could be completely crapped up--once they are out post a photo of them if you can.
Seafoam is grade A snake oil, it consists of an emulsification of:
50% light hydrocarbon oil (pale oil);
30% petroleum naphtha;
10% isopropyl alcohol;
10% water
Here is the MSDS for it.
It originated in the 50s for use in marine engines that were run cold and/or improperly stored in winter--that's the "sea" part of the name; it is rarely if ever needed in a properly cared for engine as all gasolines and motor oils have additives that prevent anything seafoam would remove from building up in the first place. I have never used it in over 60 years of owning automobiles, bikes, boats, etc.--and would not use it in a lawnmower.
There is no automaker that recommends or even approves of it's use in gasoline engines, most specifically state that such products should not be used (diesels are a different story a they burn crap and run filthy to begin with).
If your engine is running better after pouring seafoam into it then it was seriously crapped up, probably from only being driven 1500 miles a year for 12 years at 1.2 miles a pop...
Seafoam is grade A snake oil, it consists of an emulsification of:
50% light hydrocarbon oil (pale oil);
30% petroleum naphtha;
10% isopropyl alcohol;
10% water
Here is the MSDS for it.
It originated in the 50s for use in marine engines that were run cold and/or improperly stored in winter--that's the "sea" part of the name; it is rarely if ever needed in a properly cared for engine as all gasolines and motor oils have additives that prevent anything seafoam would remove from building up in the first place. I have never used it in over 60 years of owning automobiles, bikes, boats, etc.--and would not use it in a lawnmower.
There is no automaker that recommends or even approves of it's use in gasoline engines, most specifically state that such products should not be used (diesels are a different story a they burn crap and run filthy to begin with).
If your engine is running better after pouring seafoam into it then it was seriously crapped up, probably from only being driven 1500 miles a year for 12 years at 1.2 miles a pop...
Thread Starter
Junior Member
Joined: Aug 2013
Posts: 40
Likes: 1
From: Linn County MO
SL500
At two 1.2 miles a day trips for 12 years that engine never got hot enough to boil off the crap byproducts of combustion, the plugs could be completely crapped up--once they are out post a photo of them if you can.
Seafoam is grade A snake oil, it consists of an emulsification of:
50% light hydrocarbon oil (pale oil);
30% petroleum naphtha;
10% isopropyl alcohol;
10% water
Here is the MSDS for it.
It originated in the 50s for use in marine engines that were run cold and/or improperly stored in winter--that's the "sea" part of the name; it is rarely if ever needed in a properly cared for engine as all gasolines and motor oils have additives that prevent anything seafoam would remove from building up in the first place. I have never used it in over 60 years of owning automobiles, bikes, boats, etc.--and would not use it in a lawnmower.
There is no automaker that recommends or even approves of it's use in gasoline engines, most specifically state that such products should not be used (diesels are a different story a they burn crap and run filthy to begin with).
If your engine is running better after pouring seafoam into it then it was seriously crapped up, probably from only being driven 1500 miles a year for 12 years at 1.2 miles a pop...
Seafoam is grade A snake oil, it consists of an emulsification of:
50% light hydrocarbon oil (pale oil);
30% petroleum naphtha;
10% isopropyl alcohol;
10% water
Here is the MSDS for it.
It originated in the 50s for use in marine engines that were run cold and/or improperly stored in winter--that's the "sea" part of the name; it is rarely if ever needed in a properly cared for engine as all gasolines and motor oils have additives that prevent anything seafoam would remove from building up in the first place. I have never used it in over 60 years of owning automobiles, bikes, boats, etc.--and would not use it in a lawnmower.
There is no automaker that recommends or even approves of it's use in gasoline engines, most specifically state that such products should not be used (diesels are a different story a they burn crap and run filthy to begin with).
If your engine is running better after pouring seafoam into it then it was seriously crapped up, probably from only being driven 1500 miles a year for 12 years at 1.2 miles a pop...
Member
Joined: Jul 2013
Posts: 126
Likes: 5
From: Saint Augustine, FL
1998 SL500
From the 1999 Owner's Manual:
In the US any name brand pump gasoline has all the additive needed to keep the fuel system, and valves and combustion chamber clean--buying and adding other stuff just lightens your wallet. Taking the car out and running it hard for 15-20 miles (bring it up to redline at WOT a few times) will do more than will any magic elixir added to the fuel...
Thread Starter
Junior Member
Joined: Aug 2013
Posts: 40
Likes: 1
From: Linn County MO
SL500
Plugs changed.....runs great....no lights.....all is good. The old plugs looked not all that bad but they ran at low RPM for many years. The engine now runs smooth and strong. I installed the double platinum on sale at AH. Thanks for all the help with this.
