W203 engine light - annoying the heck out of me!

[mikecymru]

Hi All,

I have a 2003MY c180K W203, I had the engine light come on with code.

P0172 - bank 1 running rich
Then the odd misfire and what felt like a cylinder shutting down.
P0301 - cyclinder 1 misfire.

I have had this a couple of times but intermittent/in frequent.

My local indie, replaced the MAF last week, the car felt like a missile.. really pleased, but now the engine light has come back on and I have the misfire back. (he told me there was no boost in the pipes, and he swapped the maf there was...)

P0172 + P0302 - this time the misfire is on cylinder 2.

On top of that the auto box seems to be hunting for gears, getting very confused and giving me the occasional lumpy shift. I have a v.small oil leak from the sump gasket on it but it only took 200ml of oil topping it up... I dont think its linked to the above... any ideas. (The autobox behaved beautifully when the new maf was fitted, and until the lights came back)

Its annoying....

 

[miro]

1/ Cracked exhaust manifold

2/ Oil in engine harness (cam adjuster capillary leak)

3/ Leak in vacuum to brakes

4/ Breather hoses blocked and / or cracked (repair kit) - wedged inbetween intake

5/ Excessive oil in intake manifold (see 4/)

6/ Spark plugs contaminated (see /4)

7/ Clogged catalytic converters

 

[mikecymru]

Thanks Miro,

Its going back into the garage on Monday.... Ill get them to check your suggestions, and let you know the outcome. Cat I'd thought about and breather hoses. Vacuum leak in brakes is an interresting one.

I mentioned to the garage that I thought my braking perfromance was marginally down... linked?

I cant visualise how though....

Thanks

mike

 

[miro]

M271 and M111 are more sensitive to loss of vacuum pressure than the larger engined models. You will notice that there is a connection pipe at the intake manifold which connects to the brake booster.

 

[mikecymru]

M271 and M111 are more sensitive to loss of vacuum pressure than the larger engined models. You will notice that there is a connection pipe at the intake manifold which connects to the brake booster.

Got the car back, the garage changed a breather pipe which ran from the bottom crankcase to the manifold, but it still decided to misfire and it drives terribly, it pulls sometimes, always feels a bit strained, has really trouble deciding which gear to be in . It's gone back again , I'll keep you posted.

 

[Auto-mobile]

There is one under the supercharger to.

 

[mikecymru]

They are thinking coil pack? but there is a real air of uncertaintity I feel, seems to me like they are changing bits on a whim. Do you think the coil packs could be be to blame.?

 

[Jokuk]

Is your local indie one of the recommended on here ? Might be worth a second/alternative opinion ?

 

[Auto-mobile]

Worst case your chain could have stretched or timing jumped.

 

[Terry_]

If you are getting misfire codes and cylinders are dropping out randomly it needs to go on star and have a few thing checked
Early variants of the M271 have modified valve springs to cure misfire faults. Valve guides also need to be checked

 

[Dichtung]

If you are getting misfire codes and cylinders are dropping out randomly it needs to go on star and have a few thing checked
Early variants of the M271 have modified valve springs to cure misfire faults. Valve guides also need to be checked

Apparently M271 engines have a problem with carbon build up in the valves area if not regularly given a hard work out. Misfiring is a symptom. Been down that road.

 

[jaymanek]

The air pipe under the air filter box is the common one.. But as has bee said valves are an issue on this model as is oil in the cam magnet loom which is fixed by a repair harness that most dealers keep on the shelf...

 

[E270 Owner]

Symptoms
You will more than likely not notice any drivability problems, although there may be symptoms such as a misfire.

Causes
A code P0172 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled.

There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.

There could be a vacuum leak.

There could be a fuel pressure or delivery problem

Possible Solutions

Possible solutions include: Inspect all vacuum and PCV hoses, replace if necessary Clean the MAF sensor.
Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling.

Inspect fuel lines for cracks, leaks, or pinches
Check the fuel pressure at the fuel rail
Check the fuel injectors, they may be dirty.
Use fuel injector cleaner or get them professionally cleaned/replaced. Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)

 

[panason1c]

Is it possible a faulty lambda sensor could cause P0172 ?

 

[mikecymru]

E270 owner - I had the MAF changed as part of the investigation.
Jaymanek - apparently all of the hoses have been checked for leaks, but ill make sure they have done them all.
Oil in the harness/loom, dont think this has been checked - Ill ask.
Dichtung - Valves, I hope its not this, or its goodbye MB. What I would say is I average about 150-200miles a week.. motorway mostly so I'm struggling with the hard work out theory.
Thanks for you all you help guys, and Ill keep you posted.

 

[mikecymru]

Update : two coil packs fitted, 1 maf, 1breather hose , auto box has a leaky connector which is being done today, oil/filter/gasket change. Let's see how that works now or I maybe burying it

 

[famasfilms]

Does yours have the m111 engine or the m271.

I'm getting constant p0172 engine lights on my m111 2002 c230k. MAF sensor was replaced a few weeks ago, but it has just come back on

 

[deian]

I have c200k, and I had a maf code on mine, took it to mb-tech in Warrington and the diagnosed oil in the loom due to a leaking cam magnet, first thing I'd check is that, take the grey/white cover off the top of the front of the engine, and pull off the connector, if it has oil on it that could well throw other fault codes totally unrelated to the leaking oil down the cables, the oil in mine to all the way down to the ecu (check the connectors there too) and the lambda sensors, not good... on the other hand, oil wouldn't cause absolute havoc, just on lamda tuning circuits such as maf/oxygen sensor etc it would have a capacitive effect and u'd get bad fuel consumption., I suppose it could go the other way too

 

[M271]

Hope its sorted

 

[mikecymru]

Well, im still none the wiser after all this time. so far, theres no oil in the looms, the gearbox has been serviced, new maf, new coil packs/plugs, breather hose checked. The car is running very rich, although doesnt drive horribly it feels not right. If i push it to say legal limits and on a hill its peformance is massively down and its fuel up. Then the misfire comes and it runs on three cylinders, quick ignition off and on again reset the light and off i go again... now im thinking its mechanical, valves, timing chain, or cam lifters... any advice. (Any one know of a good MB indie i the newport area south wales so i can get a diagnosis?) cheers