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Rough Idle, Rotten Exhaust Smell, High Fuel Consumption, Codes keep on coming :-(
Hey Guys,
Having some trouble with my 2006 C350 Sport with 149k.
Background: For the past couple months I was having the classic intake manifold flap failure issue and had all the codes related to that. After installing a new intake manifold everything seemed to be working great, at least for a few weeks that is.
Now I am getting a bunch of codes and have no idea what is the root cause. After clearing the codes and starting fresh, I can drive for about 20-30 minutes before a pending code shows up. Keep in mind this is with a basic scan tool, I don't have anything specific for MB, I got the stuff for BMW (INPA/ISTA) and the VAG-COM for VW/Audi but no tricks for Benz. if there is a cable or software that I can get, let me know.
They show up in this order every 5-10 minutes.
First P2177 then a few minutes later P2179. Then P2000 followed by P2003, P2248, P2244 and then ultimately the hard code sets off the Check Engine light and P0139 & P0159 get added to the bunch.
After the first couple codes show up, the rough idle begins and the exhaust smell is pretty bad from the initial start up. It still seems to run ok but when accelerating a puff of smoke comes out of the tailpipe. Also it is burning 1/4 tank of fuel over 40 miles (mostly freeway).
I have went back through the entire intake manifold procedure to verify everything is plugged in correctly and hooked up. I cleaned up all the connections and reseated all connectors. I didn't find anything that was unplugged or disconnected. I sprayed carb cleaner around the intake manifold and vacuum lines but did not get any evidence of leaks.
Not sure what I am missing here? Any advice would be greatly appreciated.
Just off the internet,
P2177 - exhaust O2 sensor bank 1 too lean
P2178 - exhaust O2 sensor bank 2 too lean
P2000 - NOx trap efficiency low
P2003 - diesel particulate filter efficiency too low (not sure how this applies to a gasoline vehicle)
P2248 - O2 sensor reference voltage low (bank 2 sensor 1)
P2244 - O2 sensor reference voltage low (bank 1 sensor 1)
P0139 - downstream oxygen sensor (bank 1)
P0159 - downstream oxygen sensor (bank 2)
Something is off with low oxygen in the exhaust which is why the errors are apprearing in a cascade effect. My guess would be that something is causing the engine to overcompensate for a lean condition (not enough fuel, too much air), which is why the subsequent codes all have to do with low oxygen, which suggests that the engine is then running too rich. The sooty exhaust and poor mileage are telltale signs.
I would start by looking at the MAF and intake O2 sensors. I don't think your spark plugs or ignition coils are causing problems at this point, but they're coming up to their service lives anyways.
Where are you located? (country)
Last edited by slammer111; Oct 31, 2021 at 11:01 PM.
Just off the internet,
P2177 - exhaust O2 sensor bank 1 too lean
P2178 - exhaust O2 sensor bank 2 too lean
P2000 - NOx trap efficiency low
P2003 - diesel particulate filter efficiency too low (not sure how this applies to a gasoline vehicle)
P2248 - O2 sensor reference voltage low (bank 2 sensor 1)
P2244 - O2 sensor reference voltage low (bank 1 sensor 1)
P0139 - downstream oxygen sensor (bank 1)
P0159 - downstream oxygen sensor (bank 2)
Something is off with low oxygen in the exhaust which is why the errors are appearing in a cascade effect. My guess would be that something is causing the engine to overcompensate for a lean condition (not enough fuel, too much air), which is why the subsequent codes all have to do with low oxygen, which suggests that the engine is then running too rich. The sooty exhaust and poor mileage are telltale signs.
I would start by looking at the MAF and intake O2 sensors. I don't think your spark plugs or ignition coils are causing problems at this point, but they're coming up to their service lives anyways.
Where are you located? (country)
Appreciate the response, I am located in the US, Southern California. The funny thing is my generic code scanner worked just fine when I had the P2004 & P2006 intake flap error codes. I also looked up the descriptions you posted above but the problem is I can't find anything that helps point me in the right direction with regards to the initial P2177 & P2179 codes. It's just a snowball affect from that point and it just keeps finding new issues to complain about.
Maybe I got a defective Intake Manifold? It's a genuine Pierburg manifold so it doesn't make any sense but I'm stumped.
With regards to the P2003 code, some people said it had something to do with the air pump. But the thing is it is working as described, comes on only when cold start and runs for about 20-30 seconds. Has great vacuum and sounds normal. Why would I be getting a cold start code after driving around for 30 minutes?
I need to figure out what software I can access to get a better idea of the root cause, since I don't really see any info out there about the issues I'm experiencing.
You may want to put your location in your profile. Lets the rest of us know which version of the car you have.
Pierberg is a respectable aftermarket brand, assuming you didn't get a knockoff. I assume you still have the old manifold. One thing you can try is reinstalling the old manifold but with a bunch of the electronics and mechanisms from the new manifold transplanted over.
If all else fails, there is always the dealer or MB indie (someone who has the STAR computer) option for pulling codes. That will at least point you in the right direction.
Last edited by slammer111; Nov 1, 2021 at 12:37 AM.
I already expressed that I don't have experience with MB diagnostics. Maybe you could suggest options instead of just a blanket response of "Use Proper Diagnostics", not really helpful but thanks.
You may want to put your location in your profile. Lets the rest of us know which version of the car you have.
Pierberg is a respectable aftermarket brand, assuming you didn't get a knockoff. I assume you still have the old manifold. One thing you can try is reinstalling the old manifold but with a bunch of the electronics and mechanisms from the new manifold transplanted over.
If all else fails, there is always the dealer or MB indie (someone who has the STAR computer) option for pulling codes. That will at least point you in the right direction.
Thanks, I will reach out to my local indie guy to see what software he has access to.
Any options for purchasing a good scan tool that works for MB? Don't really know what is out there that gets the job done.
The MAF isn't expensive. I'd probably try swapping it out first as well. If that doesn't solve the problem then I'd look into the intake O2 sensor(s) next.
The MAF isn't expensive. I'd probably try swapping it out first as well. If that doesn't solve the problem then I'd look into the intake O2 sensor(s) next.
Be sure to go OEM or quality aftermarket only.
UPDATE:
Got the new Bosch MAF installed today. Cleared all the codes and went for a drive. Unfortunately the rough idle and smell are still present and the codes above come back after a short drive.
I decided to unplug the new MAF just to see how the car behaves with it unplugged and to my surprise the rough idle disappears and it seems to run smoother. This does not make any sense, why would it run better with it unplugged. Why would a new MAF exhibit the same characteristics as the old one.
I have looked at all of the hoses below and don't see anything obvious. I traced them to both ends and all hoses/lines are soft and flexible. The only thing that may be a little loose was the plastic elbow piece that the throttle body attaches to. The connection to the throttle body itself feels a little loose but hard to tell if anything is leaking from there. Those red o-rings still seem soft and flexible.
Brake booster line looks good.
Throttle body hose is soft and looks good.
PCV hose looks good.
What behavior should happen when I remove the oil cap?
I am not sure what the "breather caps" are on the back on the engine?
The oil dipstick o-ring is a little hard and doesn't seem to be that tight in the pipe. What size o-ring is that one, I might have something here to try out?
A quick search online suggests there may some sort of leak in your intake that is allowing in unmetered air, which would make sense since your car is running lean. Specifically check some of the many small hoses snaking around the engine around the throttle body. These hoses are known to go bad with age. Sometimes they simply pop off the nipple from vibration. I remember my car throwing a CEL when one of the hoses went bad. Didn't get to the point of stumbling, but you get the idea.
As mentioned before, you may also want to look into testing and/or replacing the intake O2 sensors as a next step. Shouldn't be too expensive.
Last edited by slammer111; Nov 15, 2021 at 09:57 AM.
I finally had a chance to work on the Mercedes today. Swapped out the PCV along with the intake elbow with brand new Mercedes units. Unfortunately those did not make any difference with the situation.
I decided to go ahead and remove the intake manifold again to ensure it was set correctly. Installed the intake manifold again with NEW gaskets along with a NEW gasket for the throttle body. I even replaced the fuel injector o-rings since that was not done the first time around.
Unfortunately all of these did not change the issue at, even the slightest. It still has the rough idle and black smoke/fuel smell is coming from the exhaust. I was afraid of just throwing parts at the attempt to solve it. Given the codes above from the "real" scan tool, it still does not help me pinpoint the issue?
At a loss here, not sure where to go on this?
New parts list:
Pierburg Intake Manifold
Intake manifold gaskets
Throttle body gasket
Fuel injector seals
MAF sensor
Intake elbow
PCV
BTW - The car once again will run without issue if the MAF sensor is unplugged. No rough idle and not black smoke/fuel smell.
You need a shop to perform a smoke test. I bet there is a loose hose somewhere. So tough with problems like this. You'll get it!
Edit: The car will run in a default software mode when you unplug the MAF sensor. It allows for the car to run in factory fuel/air settings if there is a major fault, to make sure it doesn't run lean.
Last edited by SilverSpy0; Nov 30, 2021 at 07:49 AM.
Reason: Additional info
You need a shop to perform a smoke test. I bet there is a loose hose somewhere. So tough with problems like this. You'll get it!
Edit: The car will run in a default software mode when you unplug the MAF sensor. It allows for the car to run in factory fuel/air settings if there is a major fault, to make sure it doesn't run lean.
I went ahead and purchased a smoke machine since I think it's a good long term investment to have anyways. It will make all future vacuum related leaks hopefully easier to locate.
I got my smoke machine and hooked it up to the rear vacuum port on the manifold. Unfortunately, I cannot detect any leaks coming from the intake manifold or associated hoses.
Any other places I should hook up the smoke line ?
Ok, I did both directions of the solenoid valve by the driver's side headlight. Still not detecting any leaks whatsoever. it actually builds a little pressure in the line and then blows back smoke when I unplug it.
What kind of bad smell? Burning oil? Raw gasoline? Rotten eggs/sulphur smell could be bad or clogged cats... That'd cause most of the symptoms and codes that you mention.
What kind of bad smell? Burning oil? Raw gasoline? Rotten eggs/sulphur smell could be bad or clogged cats... That'd cause most of the symptoms and codes that you mention.
Yeah it is light black smoke out of the exhaust and smells like raw fuel.
Just wanted to give an update on the repair. I ended up taking it to a local shop that has the Star software so they could perform a proper scan.
The diagnosis they came up with was the upstream O2 sensors were bad. I supplied them with the Bosch parts and went ahead and had them change them just in case their diagnosis was incorrect.
It has been a week and everything seems to be working correctly so I guess they were right. Fingers crossed that it solved once and for all.
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