OM274 Engine Missfire

[Judwin]

Hi, First real problem with me-merc. Not sure if I should be posting in DIY or Engine, so mods please move if I've got it wrong.

2013 W204 C180 OM274 (so 1.6L petrol turbo)

Noticed a very occasional slight hesitation on Saturday, heading from St Dizier to Eindhoven. No EML. However Sunday afternoon traveling from Eindhoven back to Brussels the hesitation turned into more of an occasional miss-fire, and the EML came on - sometimes solid on, sometimes flashing. There was a whiff of petrol when we got to Brussels. Once we'd done Brussels (about 2 hours) the car was reluctant to start. On the long trip home from Brussels to Somerset (via Koksijde & the chunnel) the missfire was there all the way, and the smell of fuel when stopping very marked.

It's now very slow to start, and at tickover it's very lumpy, like it's running on 3 (or even 2). It seems Ok-ish (tolerable) on light throttle. On heavy throttle it's an obvious missfire, and it struggles to maintain speed up hills. EML is now on all the time with just the occasional flashing spell. And it smells of fuel.

My initial thought diagnosis was either a fouled/failing/failed spark plug, or a failing/failed ignition coil, but without a code reader I can't tell if that really is the issue. Doubt it's fuel injector since it does smell of fuel. So...questions

1) Is it possible to flash out 'blink codes' on the dashboard somehow?
2) Any recommendations for a suitable code reader and software for this engine?
3) Any common failures that match this fault description?

Cheers
Judwin

 

[tpn]

Again, I would start with the simple things, change the plugs. You are querying them so it would appear they may not have been changed in quite a while.
Cheap and simple. Only then it is time to look at coil packs and chain issues and injection issues.

My neighbour called to me a few weeks ago. His wife's Mitsubishi Colt was misfiring, bringing on a MIL light occasionally etc.
A "mechanic" has changed every sensor in the car without success.
I asked him had he changed the spark plugs Eh never thought of that. Changed them, all was perfect.

Same trying to solve a starting problem with a suspect battery, a waste of time.
I am not familiar with that engine, so I may be completely off the mark, but its food for thought.
You will not go far wrong with an Icarsoft diagnostics unit.

 

[Judwin]

I changed the plugs about 7K miles ago (in November) - I did it myself, so I'm 100% sure it was done. Whether it was done properly is another issue..

Anyway - local garage has it now. I was there when they plugged the code reader in. Misfire on #2, something about fuel pressure sensor and fuel trims on #1,3,4 all maxed out.

Pulled the plugs, and #2 caked solid. Replaced all 4 with new plugs but ran no better. Lots of swapping of ignition coils, no improvement. Compression test and Leak Down test all Ok. Oil filler also smells of fuel.

So current theory is #2 injector has failed open and excessive fuelling has caked the spark plug, leading to misfire, bore-wash and fuel in the sump. New injector on order £360 - ouch. I'm also a bit worried about Lambda sensor and Cat damage. Will know more once the new injector arrives from MB.

 

[tpn]

Looking expensive.
I always use Dipetane in my diesel and petrol vehicles.
Great stuff. Keeps everything in great shape.
A bit unusual for two injectors to stick open at the same time.
I would clean the fuel system before installing an new items.
Again not familiar with the engine..but are they not a Renault engine

 

[ernieh]

Looking expensive.
I always use Dipetane in my diesel and petrol vehicles.
Great stuff. Keeps everything in great shape.
A bit unusual for two injectors to stick open at the same time.
I would clean the fuel system before installing an new items.
Again not familiar with the engine..but are they not a Renault engine

Very few problems on here with the M274 engine apart from the thermostat which is a beast to change. Unlike the M271, I'm not aware of any cam chain issues with this engine. Just hope for the op's sake there has been no lasting damage. Might be worth confirming that the t'stat was running up to temperature as over a period could cause a number of issues.

Ernie

 

[ernieh]

I changed the plugs about 7K miles ago (in November) - I did it myself, so I'm 100% sure it was done. Whether it was done properly is another issue..

Anyway - local garage has it now. I was there when they plugged the code reader in. Misfire on #2, something about fuel pressure sensor and fuel trims on #1,3,4 all maxed out.

Pulled the plugs, and #2 caked solid. Replaced all 4 with new plugs but ran no better. Lots of swapping of ignition coils, no improvement. Compression test and Leak Down test all Ok. Oil filler also smells of fuel.

So current theory is #2 injector has failed open and excessive fuelling has caked the spark plug, leading to misfire, bore-wash and fuel in the sump. New injector on order £360 - ouch. I'm also a bit worried about Lambda sensor and Cat damage. Will know more once the new injector arrives from MB.

The thermostats on these can fail, like any other, but are difficult to get to. Was the car showing any signs of a failed t'stat, like low or fluctuating temperature?

Hope for your sake there has been no long-term damage, as these engines are normally very reliable.

Ernie

 

[Judwin]

Dashboard engine temp gauge was in it's normal range - about the 3 O'Clock position or a little higher, but not approaching the next large graduation. I've not noticed it misbehaving, and it's up to temperature in about 5-10 minutes/miles from a cold start in this weather.

 

[Judwin]

Got the car back this afternoon. Didn't have time for a chinwag, but they are saying the only thing wrong was the injector on Cyl#2. Will find out more when I go back to pay on Monday. Car ran Ok on the way home tonight so hopefully......

 

[ernieh]

Got the car back this afternoon. Didn't have time for a chinwag, but they are saying the only thing wrong was the injector on Cyl#2. Will find out more when I go back to pay on Monday. Car ran Ok on the way home tonight so hopefully......

Glad it's sorted with no downstream problems. Might be the better of an oil and filter change though (if not already) due to petrol dilution of the oil.

Ernie

 

[Judwin]

Glad it's sorted with no downstream problems. Might be the better of an oil and filter change though (if not already) due to petrol dilution of the oil.

Ernie

Thanks, yep oil and filter change was done. New injector, 4 new spark plugs, oil and filter. Total came to £694, including the dreaded bung to the chancellor. Could probably have saved a few quid by doing it myself, but didn't really have the time.

 

[Judwin]

And the fault is back. Had to go to Ferndown this morning. On starting to do the 40 miles back to civilisation an obvious lumpy running and on moderate acceleration the same misfire as before. I've got an iCarSoft now, and it shows...

P008792 - Fuel pressure low
P030085 - Engine misfire
P030385 - Misfire on Cyl 3.

Which I'm pretty sure is the same as last time. Had a quick look through the screens on iCarsoft to see if I could find anything relevant, but nothing jumped out. So it's back with the garage now. Hmmm.

Ahh - update - last time was cyl #2. Sounds like they're popping like Christmas tree lights one after the other. So I've told them to replace all 3 of the original ones, and keep the two 'good' old ones as future spares. Doubt I'll get change from a grand.

It does make me wonder if it's E10 related though.

 

[cheapshots]

And the fault is back. Had to go to Ferndown this morning. On starting to do the 40 miles back to civilisation an obvious lumpy running and on moderate acceleration the same misfire as before. I've got an iCarSoft now, and it shows...

P008792 - Fuel pressure low
P030085 - Engine misfire
P030385 - Misfire on Cyl 3.

Which I'm pretty sure is the same as last time. Had a quick look through the screens on iCarsoft to see if I could find anything relevant, but nothing jumped out. So it's back with the garage now. Hmmm.

Ahh - update - last time was cyl #2. Sounds like they're popping like Christmas tree lights one after the other. So I've told them to replace all 3 of the original ones, and keep the two 'good' old ones as future spares. Doubt I'll get change from a grand.

It does make me wonder if it's E10 related though.

Hi Judwin,
Out of interest, what happened in the end?

I have a W212 (2013 e class, petrol) with the same m274 engine and have the same issue as you’ve described.

Thanks

 

[Judwin]

Soz, thought I had updated...

I got the garage to replace the other 3 injectors. and that has cured it (so far!). However, the CAT died about 6 months later. OK it is/was basically 10 years and 100K miles old so perhaps it was on it's last legs anyway.

The Mercedes dealership told my local garage that they had sold over 300 injectors in the past few months for this fault, so my guess is it[s a fairly common failure on this engine.

 

[cheapshots]

Thanks for the update. Really appreciated.

Having similar issues here. Replaced a few injectors and the issue persists so thinking maybe electrical / ECU now.

As you say, 10 years old and 100k mileage - bound to have issues. Thinking it might be a good time to sell!

 

[Judwin]

Thanks for the update. Really appreciated.

Having similar issues here. Replaced a few injectors and the issue persists so thinking maybe electrical / ECU now.

As you say, 10 years old and 100k mileage - bound to have issues. Thinking it might be a good time to sell!

Have you read the trouble codes with a scan tool? The iCarsoft I have sucessfully identified both faulty cylinders as having a missfire. Once it's not the spark plugs or injectors it's more or less got to be injectors.

 

[cheapshots]

The garage checked / replaced the injectors, spark plugs, coils and did a compression test in case the piston head cracked (apparently common with with M274 engine) But the problem persists

 

[cheapshots]

Small update for you... The car is now fine. My local garage changed injector number 2 and 3, and coils. £750 all in.

Sounds like the fault codes kept throwing the garage off and I think they wasted a lot of time trying to pin point which injectors / coils were at fault. E.g scanner would say misfire cylinder 4 but it was actually 2 and 3.

Do you think the other two injectors should have also been changed as two out of four have already failed?

@Judwin - sorry to hear about your CAT dying too! What a pain, I am going to use Cataclean every so often and hope it does the trick! Thanks for the heads up.
Out of interest, before you had the full on misfire issue, do you remember intermittently hearing a sort of droning / humming / air suction sound coming from the engine bay when accelerating in a gear that might be slightly higher than the car would like?

Cheapshots

 

[ajlsl600]

Looking expensive.
I always use Dipetane in my diesel and petrol vehicles.
Great stuff. Keeps everything in great shape.
A bit unusual for two injectors to stick open at the same time.
I would clean the fuel system before installing an new items.
Again not familiar with the engine..but are they not a Renault engine

Sorry to but in. Where do you get ur diptane? And the dosage is?

 

[Blobcat]

Sorry to but in. Where do you get ur diptane? And the dosage is?

Home Page - Dipetane

dipetane.com

 

[Judwin]

@Judwin - sorry to hear about your CAT dying too! What a pain, I am going to use Cataclean every so often and hope it does the trick! Thanks for the heads up.
Out of interest, before you had the full on misfire issue, do you remember intermittently hearing a sort of droning / humming / air suction sound coming from the engine bay when accelerating in a gear that might be slightly higher than the car would like?

Cheapshots

No. First signs of failure were a slight fluff/hesitation on medium throttle. No unusual under-bonnet noises that I remember.