W203 M271 C180 - Running Rich, Emissions failure.

[2v50]

Hi all - I've searched and searched to no avail to find a solution to this. My impulse bought C180 cannot for the life of it pass Emissions for MOT.
Test failure as follows -

• Exhaust carbon monoxide content after 2nd fast idle exceeds default limits (8.2.1.2 (b))
• Exhaust hydrocarbon content after 2nd fast idle exceeds manufacturer's specified limits (8.2.1.2 (a))
• Exhaust Lambda reading after 2nd fast idle outside specified limits To Low (8.2.1.2 (c))

I've replaced the deteriorated breather hoses and the upstream o2 sensor - this actually caused the emissions to be even worse!
The tester states that he has never seen CO emissions so bad, the machine usually stops at 10, it went up to 13...
Previous owner somehow got it through the same failures a few years in a row - So I assume it has been running rich for the past four years. It has only done aprox 9k miles in that time. Tester said maybe the catalytic converter has failed. DTCs prior to replacing o2 sensor but after hoses were 2029-002 and 2046-001.
This car has 101k miles on it, full sports pack ect. Drives great, other than the exhaust reeking and extreme fuel use ( quarter of a tank in 15 miles and a hour or so idling!)
Any suggestions? This car was very, very cheap - all in I'm just breaking £600 at this point. I'd like to get it running well rather than just break it for parts!
Thanks in advance!

 

[star]

Check for oil in the engine wiring harness, esp at the o2 sensors and ecu. There is a soft ware update and adaptation of o2 sensors, this takes several long road test. Did one yesterday.

 

[2v50]

Thank you!
Adaption is kind of a problem - reset with launch but no change. Taking it a drive to allow adaption is out the window as now not only does it have no MOT, it's misfiring and running rough.
The cam sensors are leaking very slightly - no contamination at o2 sensor connections but there was a drop of oil on one of the ECU connectors. Car threw up P0137 , P0304 , P0171 prior to adaptions - smoked out the entire street. misfires only at idle, runs slightly rough under load.
After clearing codes and resetting adaptation, only code is P0304 201A-004 + 201B-004 as how the launch tablet displays it. The rough running and misfiring changed slightly after resetting adaptions. It stops for a very small interval if build the revs then allow to drop off.
Downstream o2 sensor randomly goes from 600~mV to nothing. Upstream reads 1248~ mV or close to it. Can't say I'm familiar with correct values of an o2 sensor - 1000mV I believe?
I attempted to recheck for vacuum leaks the old fashioned way - starter spray. No affect.
I'm seeing why I got it for £300 at this point!
Is cleaning the harness worthwhile? It's seeming like the most obvious cause of the issue.

Thanks yet again, all help is appreciated!

 

[Steve@Avantgarde]

Sounds like a stretched timing chain to me throwing the cam timing will affect the variable timing which in turn will make the car run rich all of the time.

I would remove the rocker cover, time it up to OT on the crank and see where the camshaft markings are.

 

[2v50]

Thanks Steve, I'll get the rocker cover off once there's a dry day. Watching the timing advance on live readouts is wild. Seems to sit around 13.5 degrees advanced but I saw it as high as 63.5, if the readout is to be believed - first car I've had where I've actually looked ( and only the second with VVT ! )
Misfire turned out to be the simplest option - #4 spark plug was fouled with fuel. Running smooth as anything again, other than puffing out smoke like crazy. I'm very curious as to if there would be anything more caused by the timing being out? it appears to have been done in the past, if paint pen markings are to be believed.
On a side note , does the MAF sensor have the air intake temp sensor built in? Just as the readouts are 27-33 degrees, with a hot or cold engine - outside temperature was 11 degrees!

weirdly this never posted yesterday, so here's todays update- the air intake temp was accurate today.
Does anyone know what the MAF readings should be? I'm getting 3-3.4 g/s once its warm, on startup I'm getting 14 g/s dropping off fairly quick. If i pull the topmost breather to induce a vacuum leak it drops to 2.6-2.8g/s - no change to idle. applying the throttle even a little takes it up rapidly, 20 g/s at 3700rpm.
Car is no longer smoking madly , yet again. Yesterday while warm the maf was sitting at 4.9 g/s idle.
Without any reference values I'm not sure what I should be expecting - a youtube video showed reference values of 7-16 kg/h , which is within range. Really hoping it's not the timing, liable to end up as scrap if it is!

 

[2v50]

Checked the timing today, looks to be spot on. Looks slightly offset in the photos , but to the eye it looks dead on. The teeth on the cam sprockets look fairly worn though.
Is my next port of call replacing / cleaning the wiring harness? Or is this wear the cause? Checked with another MAF sensor, readings much the same.
Thanks again

 

[Blobcat]

That chain looks like it’s twisted and pulling more on the top than the bottom - got to love simplex chains…

 

[tpn]

If it is not a timing issue put a bottle of Dipetane into the tank,( its a natural product so you cannot overdose) take it for a 10 mile spin and straight into the MOT station.
Dipetane is magic.

Several months ago a family member took her Audi A1 sport with less than 10k miles on it for MOT.
It failed miserably on the emissions. Garage told her that the Oxygen sensor was goosed and a new one was £162.00 plus £100.00 or so fitting.

I told her no way. She put a half a bottle of dipetane into it, took it for a spin, straight to the MOT station. It passed with zero emissions.
They were gobsmacked. Its only £12.00 or so for a litre, so it will not break the bank.

 

[2v50]

Blobcat - It went like that from slack the moment the engine was turned over. Any idea of what the chances are that is what is causing it to run rich?
tpn - I'll keep it in mind, but with the confirmed rich condition I think that Dipetane is very unlikely to do much. £12 won't break the bank - but insuring it and taking it for another test just to fail and need work will! I'll throw a bottle of it in once I can get it to tell me it's not either overfueling or failing to combust.

Side note, any idea what the short term fuel trims should ideally be sitting around at idle ? mine seem to sit at adding extra fuel in at idle and trimming all the way back when under any load.

Thanks again - every possibility or thought is really appreciated. I may have chosen the most... interesting... way into Mercedes ownership!

 

[Wighty]

Blobcat - It went like that from slack the moment the engine was turned over. Any idea of what the chances are that is what is causing it to run rich?
tpn - I'll keep it in mind, but with the confirmed rich condition I think that Dipetane is very unlikely to do much. £12 won't break the bank - but insuring it and taking it for another test just to fail and need work will! I'll throw a bottle of it in once I can get it to tell me it's not either overfueling or failing to combust.

Side note, any idea what the short term fuel trims should ideally be sitting around at idle ? mine seem to sit at adding extra fuel in at idle and trimming all the way back when under any load.

Thanks again - every possibility or thought is really appreciated. I may have chosen the most... interesting... way into Mercedes ownership!

As @Blobcat said , those chain links look well out of alignment .
would it be worth a chain replacement just to rule that out as an issue ?

 

[2v50]

I'm feeling outdated here. Working reply functions and tagging users! Too used to forums where none of that works or just isn't there.

As @Blobcat said , those chain links look well out of alignment .
would it be worth a chain replacement just to rule that out as an issue ?

In for a penny in for a pound I guess. £300 car price, £55 MOT, 120 odds service kit, £26 for the vacuum hose, £55 for a coil spring, a few odds and ends, £75 on insurance... I've proved I must want to keep it at this point. I bought it intending to brake it for parts till I got in it and drove it. A stunning drive, knocks my Accord flat - though its a bit slower!
I'll look into throwing a timing kit at it - if it's not that I'll be disheartened but surely there's not much else it can be - it's not even throwing any codes now. Just smoking away to itself and burning fuel like crazy. Still can't quite believe it used a quarter of a tank in 15 miles and a bit of time idling.
Thanks again!

 

[tpn]

Do not underestimate the power of Dipetane. It is magic. This is a 271 engine so it has variable timing. I cannot see the inner mark lining up in one of those photos. I have just looked at it on the big screen, but maybe I am wrong. These gears at the top (simplistic explanation) fail and allow too much movement between the parts. -I presume that you checked that the flywheel was at TDC (0), No 1 piston at the top and you turned the engine in the direction in which it runs. Those gears can fail dramatically. I know that there is a good youtube video explaining them.I will look for it.
When booking the next MOT do it with a garage that allows a free retest.

 

[tpn]

Found it

 

[Snake Charmer]

Hard to tell from the photos, has the exhaust cam gear collapsed as it doesn't look square to the camshaft?

 

[Steve@Avantgarde]

That chain is knackered IMO.

Turn it over by hand and see what happens. If you get a huge klack noise, the gears have had it as well.

 

[2v50]

Do not underestimate the power of Dipetane. It is magic. This is a 271 engine so it has variable timing. I cannot see the inner mark lining up in one of those photos. I have just looked at it on the big screen, but maybe I am wrong. These gears at the top (simplistic explanation) fail and allow too much movement between the parts. -I presume that you checked that the flywheel was at TDC (0), No 1 piston at the top and you turned the engine in the direction in which it runs. Those gears can fail dramatically. I know that there is a good youtube video explaining them.I will look for it.
When booking the next MOT do it with a garage that allows a free retest.

I will try Dipetane at some point -if its as good as you say it will become a frequent purchase. The inner mark is lined up on both sides on each photo. Phone camera lens is cracked and distorting things slightly which isn't making my photos very useful - I'll pull the cover off again if it would actually stop raining for more than half an hour while I'm around, and get pictures with a proper camera.

That chain is knackered IMO.

Turn it over by hand and see what happens. If you get a huge klack noise, the gears have had it as well.

No sound when i turned it to line up timing. Engine runs fairly quiet, seems to run perfectly other than being so rich it's fouling everything. As long as spark plugs are clear it seems fine - no lack of power from what I can tell. Mechanic who has seen it hasn't worked on this engine before but doesn't believe its timing related - I've been told to swap injectors round, see if taking the injector from #4 and moving it causes the other cylinder to get soaked. as it's the only spark plug that was wet with the misfiring.
I'll turn it over when I get the chance see if there's any noise and watch how the chain moves. Again one for better weather, frustratingly
Thank you again all !

 

[tpn]

You can possibly have failing camshaft sensor magnets. Over fuelling is one of the problems that they create and the leaking oil travels along the loom and damages o2 sensors etc.
I am glad you qualified that the camera lens is broken as otherwise the sprocket looked twisted

 

[2v50]

Turned out the lens had a adhesive glass cover on it. Explains why the phone hasn't taken a single decent picture since I got it. Crack on it was making it worse! Certainly with the mk. 1 eyeball the sprockets were sitting true from what I could see, everything turned over nice though I'll be checking again anyway.
Swapped #4 injector onto #1 as repeated short tests show only #4 spark is wet with fuel- other 3 spark plugs are a little sooty but not wet with fuel. Issue does not lie with the injector as it remained the same. Burning fuel like crazy with somewhat random smoke - it reeks of fuel all the time though.
The sensor magnets are 100% leaking - not much. A very, very small amount of oil in the loom - none at the o2 sensors but there was oil in the sensor magnet connectors.
It's sounding like a likely option. Not sure why its just #4 getting drowned but the rapid soot build-up on all the plugs suggest it's across all cylinders - the intake valves looked to be seated fine when doing the vacuum lines though just looking isn't an ideal gauge! The fuel consumption is extreme, but erratic - so is the amount of smoke produced. It usually makes some - but sometimes it will be huge clouds that fill the street.
I did a little looking into them and the erratic aspect that's becoming more obvious seems to fit the bill.
Time to price them up I guess - is there any test beyond applying voltage to open/close the solenoid?
Thanks again!

 

[tpn]

Erratic consumption would suggest that its time to look at the VVT...if only to eliminate it though I think it is the culprit

 

[2v50]

Hi again all - I could have sworn I'd already posted but it seems not. New cam magnets on, issue persists - the old ones were again wet with oil inside the plug when I disconnected to remove. Next step seems to be the engine loom? If anyone has any suggestions they will be greatly appreciated. Sitting for so long can't be doing the poor car any good!
as always,
thanks again!