SL/R230: Check Engine Light
07-22-2017, 03:18 PM
#1
Member
Thread Starter
Check Engine Light
Hi Folks,
Last weekend I was driving my 2004 SL500 (67K miles, regularly maintained). I put my foot down to pass another car. The engine stumbled and the check engine light came on.
We got home, with the engine running rough. I stopped and started it again and it ran a little smoother, but the check engine light was still on. I drove it down to my indie. It ran OK, but didn't feel 100%.
Indie said I had a misfire on 3 cylinders and he suggested a new set of plugs.
That didn't fix it, so he suggested a new set of HT leads. That seemed to have fixed it, and it came home.
This morning I took it for a drive. It was running nice and smooth at regular speeds, so I found a piece of road to open it up.
When I put my foot down, the same happened - stumble, check engine light came on, misfiring.
I pulled over, switched off and restarted and that seemed to cure the roughness, but it doesn't feel 100%.
Any thoughts before I take it back on Monday? The indie can pull codes and usually gives me a run down, but this time he hasn't given me anything specific, just misfire on several cylinders.
Any help appreciated.
Gary
Last weekend I was driving my 2004 SL500 (67K miles, regularly maintained). I put my foot down to pass another car. The engine stumbled and the check engine light came on.
We got home, with the engine running rough. I stopped and started it again and it ran a little smoother, but the check engine light was still on. I drove it down to my indie. It ran OK, but didn't feel 100%.
Indie said I had a misfire on 3 cylinders and he suggested a new set of plugs.
That didn't fix it, so he suggested a new set of HT leads. That seemed to have fixed it, and it came home.
This morning I took it for a drive. It was running nice and smooth at regular speeds, so I found a piece of road to open it up.
When I put my foot down, the same happened - stumble, check engine light came on, misfiring.
I pulled over, switched off and restarted and that seemed to cure the roughness, but it doesn't feel 100%.
Any thoughts before I take it back on Monday? The indie can pull codes and usually gives me a run down, but this time he hasn't given me anything specific, just misfire on several cylinders.
Any help appreciated.
Gary
07-22-2017, 03:53 PM
#2
MBworld Guru
You might want to invest in your own code reader. You can buy a cheap generic OBDII for $30 or less, but for about $120, you can get iCarsoft i980 which will read all MBZ-specific codes, also read from all of the car's proprietary systems (ABC, SBC, SRS, ESP, etc.)
With misfires, my advice it so start by swapping ignition parts and see if the error stays with the part or the cylinder. I'd start by swapping the coil form an misfiring cylinder to one with no error. If the error moves with the coil, replace the coil. If it stays with the cylinder, then sway plug wires. If it stays with the wires, then replace wires, if it stays with the cylinder, then swap plugs. If it then stays with the cylinder, start investigating injectors.
With misfires, my advice it so start by swapping ignition parts and see if the error stays with the part or the cylinder. I'd start by swapping the coil form an misfiring cylinder to one with no error. If the error moves with the coil, replace the coil. If it stays with the cylinder, then sway plug wires. If it stays with the wires, then replace wires, if it stays with the cylinder, then swap plugs. If it then stays with the cylinder, start investigating injectors.
07-22-2017, 07:35 PM
#3
Member
Thread Starter
Check Engine Light
Thanks Rudeney,
We have eliminated plugs and wires so I guess it's coil and injectors next. The swap strategy makes a lot of sense.
You're right, it probably makes sense to be able to interrogate the car myself even if I'm not going to carry out the repairs. I will investigate further.
Gary
We have eliminated plugs and wires so I guess it's coil and injectors next. The swap strategy makes a lot of sense.
You're right, it probably makes sense to be able to interrogate the car myself even if I'm not going to carry out the repairs. I will investigate further.
Gary
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NiceMerc (07-24-2017)
07-26-2017, 02:01 PM
#7
Member
Thread Starter
Car was in the shop yesterday. We talked about coils and injectors as potential suspects. They said they very rarely see bad injectors so coils were top of the list. They ended up replacing two. No obvious signs of damage, but like the plugs and wires they were probably original, so we're putting it down to old age.
New plugs and wires noticably improved the idle and general running. I thought it was smooth before, now it's really smooth.
My iCarsoft i980 should arrive today. I will be a little more informed next time.
The car is gradually taking me through all the typical problems for a 2004. It's an interesting journey. Love the car, I smile every time I drive it and you can't put a price on that. I'm also lucky to have a really good indie who works with me when it needs attention. I'm planning for an ABC overhaul in the fall. Replacing the dampeners and any hoses that are showing signs of age. Not sure if I will do a valve rebuild at the same time. So far, no signs of drooping...
Thank you guys for the input. Much appreciated.
Gary
New plugs and wires noticably improved the idle and general running. I thought it was smooth before, now it's really smooth.
My iCarsoft i980 should arrive today. I will be a little more informed next time.
The car is gradually taking me through all the typical problems for a 2004. It's an interesting journey. Love the car, I smile every time I drive it and you can't put a price on that. I'm also lucky to have a really good indie who works with me when it needs attention. I'm planning for an ABC overhaul in the fall. Replacing the dampeners and any hoses that are showing signs of age. Not sure if I will do a valve rebuild at the same time. So far, no signs of drooping...
Thank you guys for the input. Much appreciated.
Gary
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08-17-2017, 07:07 PM
#9
Member
Thread Starter
Check Engine Light - continued
An update...
With new plugs, wires and 2 new coils in place, things were fine for a few days, then one hot afternoon I put my foot down and got the same stumble and check engine light.
By this time I had my iCarSoft i980, so I plugged it in and started scanning. I found a generic misfire code for cylinder 5 but nothing more specific.
I cleared the code and used the car for a few more days and found I was able to recreate the problem when the car was hot and cylinder 5 was the problem every time.
I took it back to my indie, told him what I was seeing and suggested a new coil on #5. He told me the new coils they put on last time were on #5 and #7, so he would make sure the new coils weren't bad and then investigate further.
He was able to recreate the problem. The car had to be hot, then you gradually keep feeding in the power. About 5000 RPM and 60MPH it would stutter. They were seeing misfires on #5 and #7. Exactly where they put the new coils.
Switching coils didn't solve the problem so we moved on to injectors. New injectors on #5 and #7 and, no difference :-(
I usually get an update from them every day, even if it's to say 'nothing new, we're still working', but now they went very quiet on me. I was getting a little worried.
Today they called to tell me that they had reached out to their Mercedes mechanic network, described the problem and got many replies. Most were along the lines of plugs then wires then coils then injectors, just as Rodney suggested here.
Fortunately one or two replies pointed to a bad cat. They put the car in the air and tapped away at the exhaust and sure enough, the left cat - the one fed by cylinders 5 to 8 - is rattling.
They gave me a detailed technical explanation that I don't think I fully understood. Something like the bad cat resulting in bad back pressure which results in a bad fuel air mix/vortex. On overrun this results in poor ignition and a misfire.
They will fit the new cat tomorrow and hopefully we have chased this problem to resolution.
It's not a cheap fix, but I'm looking forward to getting the car back.
He mentioned that the local parts supplier had 7 cats in stock, which he thought was a lot to have sitting on the shelf - given how expensive they are - which and maybe an indication that they are starting to fail on R230's on this age.
Gary
With new plugs, wires and 2 new coils in place, things were fine for a few days, then one hot afternoon I put my foot down and got the same stumble and check engine light.
By this time I had my iCarSoft i980, so I plugged it in and started scanning. I found a generic misfire code for cylinder 5 but nothing more specific.
I cleared the code and used the car for a few more days and found I was able to recreate the problem when the car was hot and cylinder 5 was the problem every time.
I took it back to my indie, told him what I was seeing and suggested a new coil on #5. He told me the new coils they put on last time were on #5 and #7, so he would make sure the new coils weren't bad and then investigate further.
He was able to recreate the problem. The car had to be hot, then you gradually keep feeding in the power. About 5000 RPM and 60MPH it would stutter. They were seeing misfires on #5 and #7. Exactly where they put the new coils.
Switching coils didn't solve the problem so we moved on to injectors. New injectors on #5 and #7 and, no difference :-(
I usually get an update from them every day, even if it's to say 'nothing new, we're still working', but now they went very quiet on me. I was getting a little worried.
Today they called to tell me that they had reached out to their Mercedes mechanic network, described the problem and got many replies. Most were along the lines of plugs then wires then coils then injectors, just as Rodney suggested here.
Fortunately one or two replies pointed to a bad cat. They put the car in the air and tapped away at the exhaust and sure enough, the left cat - the one fed by cylinders 5 to 8 - is rattling.
They gave me a detailed technical explanation that I don't think I fully understood. Something like the bad cat resulting in bad back pressure which results in a bad fuel air mix/vortex. On overrun this results in poor ignition and a misfire.
They will fit the new cat tomorrow and hopefully we have chased this problem to resolution.
It's not a cheap fix, but I'm looking forward to getting the car back.
He mentioned that the local parts supplier had 7 cats in stock, which he thought was a lot to have sitting on the shelf - given how expensive they are - which and maybe an indication that they are starting to fail on R230's on this age.
Gary
08-23-2017, 12:17 PM
#11
Member
Thread Starter
Check Engine Light - resolved
Looks like it was the cat.
Indie replaced it and kept the car for a couple of days so they could run tests morning and afternoon on different roads and temperatures.
All good.
So if your SL misfires and you get code P030x, the list of things to check is:
Plugs
Wires
Coils
Injectors
Catalytic Converter
With the first 4 in the list Rodney's switch strategy is a good way to troubleshoot without throwing parts at the problem too soon.
I've ended up with new plugs and wires, 2 new coils and injectors as well as the cat. They also found the motor mounts were bad so they took care of those as well. The car feels like new :-)
Gary
Indie replaced it and kept the car for a couple of days so they could run tests morning and afternoon on different roads and temperatures.
All good.
So if your SL misfires and you get code P030x, the list of things to check is:
Plugs
Wires
Coils
Injectors
Catalytic Converter
With the first 4 in the list Rodney's switch strategy is a good way to troubleshoot without throwing parts at the problem too soon.
I've ended up with new plugs and wires, 2 new coils and injectors as well as the cat. They also found the motor mounts were bad so they took care of those as well. The car feels like new :-)
Gary
