illfoo

Hey guys,

New member here, I've lurked these forums for several months before I registered (today) and everyone here seems extremely knowledge, so I hoping I might be able to get some opinions on a problems I'm having.

I'm not terribly knowledgeable with regard to engine/auto repair, so I'm hoping you'll bear with me.

Background: Purchased a 2010 C300 W204 in August of 2015. Car ran beautifully until about a month ago, when the CEL came on and the car started running rough. The exhaust started making a slight gurgling sound and would idle rough. It also appeared to be losing power somewhat and performance wasn't typical. Over the next few days, the gurgling/sputtering got worse and car began to idle roughly. I hooked it up to my scanner and it threw up several codes, including the following in this order:

1) P2A00 O2 Sensor Circuit Range/Performance, Bank 1/Sensor 1

2) P2196 O2 Sensor Signal Biased/Stuck Rich

3) P0300 Random/Multiple Cylinder Misfire

And then so on and so forth, indicating misfires in cylinders 1-3. Again without being extremely knowledgeable in this area, I'm figuring I have a bad 02 sensor relaying bad info to the computer (probably an bad ignorant assumption).

At that point, I scheduled an appointment the local shop... and the day I go to drive it in, the CEL started flashing and car lost a LOT of power. I pulled over, shut off the car and had it towed the shop. That was a few days ago.

Shop runs diagnostics on the vehicle and advises that I have a bad ignition coil and three bad injectors on right bank 1-3. Shop proposes/indicates the following work, which I approve and which they then completed:

"Work Performed - Scan for codes, diagnosis as needed, Performed compression on cylinders 1 through 3. 150 PSI all three. Swapped sparkplugs to side to side. Swapped ignition coils. Replaced one ignition coil which was bad. Check for vacuum leaks. Checked injection pulse on number three injector to be good. Ignition coil on cylinder 4 right now. Tested gas to have no water in it. Would replace injectors one through three. Had codes 0632, 0636, 0649, 0641, 0648 all misfire codes. Also had 2349, and 0776 codes. Cleared codes. Replaced injectors on right bank. Did smoke test before injector replacement."

So, shop completed that work, test drove vehicle shortly without issue, and called to say vehicle was ready. I picked vehicle up, get literally 2 miles down the road and the CEL illuminates again and car starts acting the exact same as before and I then head riiiight back to the shop as it is obviously in no shape to be driven.

Today I get a call back, the shop is now saying the vehicle has a bad catalytic converter. Shop called the local MB dealer who advised they cannot get an OEM CC right now and can't get the vehicle in the shop until mid-JUNE. The shop is saying they can bypass/take out the damage cat, making the vehicle driveable again until it can be taken to the dealer in June. This seems to me like it would screw with the 02 sensor as well and affect info going to the computer?

Given that the shop failed to find the problem in the first place, I want to make sure I'm not just throwing money at this thing *hoping* to find the solution.

I hoping someone might have some thoughts on the above i.e. does that sound right?

Apologize for such a long post, I searched but couldn't find a whole lot! Thanks in advance!

Plutoe

New folks always stop by when they got the shaft from guys grazing sheep behind their shop---remember you pulled the faults---did you ever find one for injectors and or coils---no you had three emissions related faults which you totally disregarded--then you let some rag head convience you otherwise---that's a shame.

Get the car outa there and find a local experienced repeat experienced muffler shop that does stainless welding and have him replace the cats and get on with your life!!

IGB

I don't see where the guy asked for someone to rip him a new one, but whatever... In his defense, and to further establish that OBD-II codes aren't always as accurately diagnostic as they were intended to be, I had a run with OBD-II codes that included:
* random misfires on all cylinders, specific cylinder misfires (1 through 6)
* BOTH catalytic converters being "below threshold", which, by your analogy would have required replacement of both cats - an expensive proposition to say the least-
* random bank 1 or bank 2 lean conditions...
* several random unheard of/undefined codes..

At the end of the day, it ended up being a bad Intake Manifold and one which could not be detected by a smoke test or any vacuum test, because it was a broken flap actuator and not a compromised vacuum hose/connector.

Somebody can correct me if I am wrong but none of these codes are defined for Mercedes Benz:

Which might mean that they are "misfire codes" as indicated but it could also mean they are something completely different that a standard OBD-II code reader could not read but ones that the Xentry system could better pinpoint.

What codes is it throwing now?

I don't know what this is supposed to mean or what they used it as a substitute for.. But that does not make sense whatsoever...

For one, I know you'd be crazy to pay dealer price for a catalytic converter... The cats alone are an expensive part and to pay dealer mark up on top of that would be throwing money away...

I don't know what state (or country) you are in but if you post that, you might get some direction on where you might find some cheaper OEM parts.

That said, I still think you have got some more diagnostics to do.... As it stands right now, and unless you have some definitive information indicating bad cats, you'd be well advised to try less expensive possbilities.

Good luck.. And welcome to MBWorld...

jbt56

If your car did have the various injection/electronic issues listed, the cat(s) could very well have become damaged. Really, that's what almost always damages converters- they almost never fail all by themselves.

It sounds very odd that MB wouldn't be able to get cats for several months; you might check with your local dealer on that. Also, as others have said, depending on your location, you might be able to have a muffler shop put aftermarket converters on the car- they won't be anywhere near as good as actual MB cats, but as long as they're the best you can get, they should be adequate. I would recommend staying away from inexpensive "high flow" cats, as those will almost certainly trigger your MIL (check engine light) again.
If you can get it there, too, the dealer should run a diagnostic, just to see what they come up with.
Good luck!

illfoo

Thanks guys, I appreciate all the responses so far. After some additional research, the codes indicated by the shop (0632, 0636, 0649, 0641, 0648) are all related to misfires. Code 2349 = component G3/4 right o2 sensor before TWC has malfunction. Code 0776 = signal of o2 sensor upstream of catalytic converter of right cylinder is shifted towards rich. Those appear to be all similar to the ODBII codes that I received earlier. I thought it odd that the shop didn't address the last two codes at all, but it is my understanding those o2 sensor codes can be almost like a "false positive" being triggered by an underlying problem, so I didn't think much of it.

IMO, I'm trying to logically think through this based on what I know so far (admittedly very little) and it appears to me that if the cat is indeed damaged it would be a symptom, not the cause of my original problem. I'm wondering if the failure of right o2 sensor is causing an incorrect air/fuel mixture which then caused the misfires which then caused possible damage to the cat con. Is that at all a possibility?

As to the codes it is throwing right now, I'm not sure at the moment. Vehicle is still at the shop and we didn't discuss what the codes were today... I thought it prudent to consult some other opinions before proceeding any further.

Also, I live in IL and I'm fairly certain I could find a shop to replace with an aftermarket cat con for what I'm sure would be much cheaper than whatever the dealer would try to charge. I guess my next step would be touch base with the shop again tomorrow and see what codes are now coming back and what is their reasoning behind the cat con being the culprit of my problems.

Again, thanks for all the responses, it is very much appreciated!

IGB

Very true, although the OP makes a great point in that regard:

So if the car is throwing similar combination of codes as it did before, then it would lead us to the question of if the cats failed, there are specific OBD-II cat failure codes that have not appeared in this case.

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

through

P0439 Catalyst Heater Control Circuit

And others...

My point in those regards was this... Although the list of generic OBD-II codes might show those codes being described as such, each vehicle manufacturer can program its related codes to meet those descriptions, but they could also skip over a few and not define them for the cars they manufacture.

As an example, and for my 2008 C300, here is the one page (of several pages) of Mercedes Benz's defined OBD-II codes that are in the same range as the ones you listed:



And see, with the exception of the P0300 & P2196, none of the other codes are listed. This list also shows "MB DTC" which is what a dealer's diagnostic system would be reading.

So you plug a generic OBD-II code reader to a Mercedes Benz, and just because it reads that you have "0632, 0636, 0649, 0641 & 0648", it does not necessarily mean that those are the codes that are present. It simply means that the code reader has obtained some information that it, or the app you may be using to translate that information, has determined it to be one, or a combination of those particular codes. It could possibly be correct, in that it could indicate a problem with those particular components, but it could also mean something completely different.

And with that said, so much for OBD-II being "a standardized system to simplify diagnosis of vehicle related problems", as it was originally intended to be!

Exactly...

Keep us updated...

Edited to add: Are you using a regular code reader or do you have one of those bluetooth enabled adapters along with an app that you download and use?

IGB

Just as an added example of how far off generic OBD-II codes could be compred to MB's designation, if you were to look up a generic P0522, you will find the standard:

P0522:

Generic: Engine Oil Pressure Sensor/Switch Low
Chrysler: Oil Pressure Sensor Low Input Conditions
GM: Engine Oil Pressure Sensor Circuit Low Input Conditions

MB: Diagnosis of tumble flap intake manifold open circuit of sensor lines tumble flap shafts stick in nonactuated position

Keep in mind that for my 2008 C300, there is no "Oil Pressure sensor or switch".

Going back to MB's DTCs, you'll find that the same description "Diagnosis of tumble flap..." is listed under MB DTC code "522" (not P0522) and the corresponding OBD-II DTC code is in fact "P2006".

Isaiahadams905

What catalytic converter was it? The one on the moter or the ones under the car because I know there 4 of them but witch' ones were pisificly needed up for you??