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Having issues with this mercedes at first had a few Codes I'll attach them here but it had a maf sensor fault so replaced and deleted Codes still has a rough idle on cold start I then removed intake pipes and had oil in throttle body so cleaned that and carried out a throttle body relearn and it sat perfectly at idle for about 15 seconds and then back to having a rough idle I did have an 02 sensor fault which hasn't come back but checked voltages on them and will attach results here I'm unsure where to look next apart from vacuum leaks has anyone got any more info this car is driving me mad😭 Codes found in car before maf sensor replacement cleared Codes and none have come back
I am not familiar with the M271 engine so wont be much help.
What brand maf did you install, a Genuine Mercedes?
What OBD scanner are you using, I cannot tell. Is it a Mercedes specific scanner?
I would keep driving it until you get some codes that can point you in the right direction. But since you arent getting any codes and its a rough idle im thinking like yo said a vacuum leak issue perhaps, or PCV issue. Are you noticing any smoke coming out of the exhaust?
It's over 100,000 miles apparently it has had the engine rebuilt and is still causing the same issues but I can't see much that has been replaced it's been to 3 different mechanics and no one has solved it so now I am determined! The sparks and coils were changed with no help! I will check for vacuum leaks I've ordered a smoke tester so hopefully that helps fuel trims seem somewhat okay i will get a reading and post back with them! It's literally only really on cold start it's not bang on when warm but much much better i will get a rpm graph too to show everyone I also have ordered a new compression tester as mine is shot so when the smoke and compression tester come which should be tomorrow I can get more info on that side of it the only Codes that I had come up were steering column and instrument cluster can bus Codes! What's the best way to test the pcv on these does anyone know?? The thing is I lt had alot of oil in the intake so I cleaned it and then made the throttle body relearn itself through a service function on my launch scanner and it ran perfectly for all but 15 seconds and then went straight back to being rough which has me thinking it's more of an electrical fault than a vacuum one I may be wrong but surely vacuum will cause the issue to stay until it's no longer leaking? It's driving me mad and where it's had loads of work done at multiple different places I don't know what had been replaced with what parts! I do no that the exhaust side camshaft position sensor is leaking oil. It also has an exhaust leak which I need to locate but he didn't have time for me to get it in the air to find it but it sounds like its coming from post cat! Thank you all for getting back to me I appreciate it!!
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Looks like you are headed in the right direction. But please list your vehicle (model, year, engine) and location in your profile.
You may need professional diagnosis if you the smoke and compression tests don't reveal any cause. I recommend you contact @BenzNinja at www.benzninja.com and/or info@benzninja.com.
Do I understand correctly that it’s only rough idle on cold start? So then everything is okay after a few minutes?
If so, the problem only occurs during open loop when the engine is running on pre determined fuel/air/timing settings. Then when the engine goes to closed loop, the ECU is able to compensate for however far out of tolerance the responsible components are.
In this case fuel trims, as @CaliBenzDriver mentioned, can be very helpful in diagnosis. Although they will not be very useful during open loop as the cats are not up to temperature, when the engine is in closed loop they can be very helpful in detecting failing injectors and air leaks.
Correct me if I am mistaken, but your car is a 2007 CLK200 Kompressor with the M271 KE18ML supercharged engine. The supercharged 4 cylinder engines in the C Class cars were also in the W203 models. The 4 cylinder W204s are often M271 DE18LA turbocharged engines as that was the only 4 cylinder W204 in the U.S. market. So you might want to duplicate your original post on that forum to broaden your audience.
I have measured fuel trims they are finecompression is finePcv is fineNo vacuum leaks tried from all different areas hot and coldOnly thing I am unsure of is the throttle body I have 2 videos i made it learn the stop again and removed it completely it has slight play almost like its free movement for a degree or twoit also clicks when ignition is on this may be normal but I am unfamiliar with these enginesit won't let me upload a video on here for some reason but it pushed it self shut fully when learning but when you turn it of it never reaches that point and i also put my fonger against it running and it seems to smooth the engine idle out im unsure if this could be the cause as it is much better when warm the clicking is loud when ignition is on and stops when you start it but it seems as though the slight play in the throttle body could cause it but I'm not sure
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by Bennnnnn
I have measured fuel trims they are finecompression is finePcv is fineNo vacuum leaks tried from all different areas hot and coldOnly thing I am unsure of is the throttle body I have 2 videos i made it learn the stop again and removed it completely it has slight play almost like its free movement for a degree or twoit also clicks when ignition is on this may be normal but I am unfamiliar with these enginesit won't let me upload a video on here for some reason but it pushed it self shut fully when learning but when you turn it of it never reaches that point and i also put my fonger against it running and it seems to smooth the engine idle out im unsure if this could be the cause as it is much better when warm the clicking is loud when ignition is on and stops when you start it but it seems as though the slight play in the throttle body could cause it but I'm not sure
I have measured fuel trims they are finecompression is finePcv is fineNo vacuum leaks tried from all different areas hot and coldOnly thing I am unsure of is the throttle body I have 2 videos i made it learn the stop again and removed it completely it has slight play almost like its free movement for a degree or twoit also clicks when ignition is on this may be normal but I am unfamiliar with these enginesit won't let me upload a video on here for some reason but it pushed it self shut fully when learning but when you turn it of it never reaches that point and i also put my fonger against it running and it seems to smooth the engine idle out im unsure if this could be the cause as it is much better when warm the clicking is loud when ignition is on and stops when you start it but it seems as though the slight play in the throttle body could cause it but I'm not sure
I cannot find a vacuum line does anyone have a diagram to show me where it is even supposed to go?
The map sensor I'm looking at is 30 on the diagram but I cannot find anything to show where the vacuum line should be
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Cold start rough idle please help
