[Bnut]

Hello folks,

This is w245 B1700 petrol 2005/6 with no history, basic runaround.

Cylinder four has a miss determined by pulling HT, removed plug - gap looks huge at 1.1mm although OEM plugs are set to 0,9m which I assume is just under 1mm, not 100% sure as separated by a comma, perhaps denoting something different?

If someone could confirm correct electrode gap that would be great, ordered a set of Bosch which should be here tomorrow.

The coil packs which feed 3/4 has two coils, are these independent of each other, i.e could one coil fail (out of the two) leaving the other working fine?

Complete newbie on this stuff as owned a S124 dinosaur for an age

Thanks for any pointers.

 

[Bnut]

Plugs arrived early, popped those in (real job getting caps off) no change - taped cylinder 4 plug to engine and started, plenty of spark so looks like coil pack okay.

The catalytic convertor is starting to whiff, possibly due to unburnt fuel making its way back ?

 

[Bnut]

It looks as though fuel is being burnt inside the cat which is getting super hot.

I may have answered my own question regarding coils, it looks like each plug has one coil each independent of the other, this may explain cylinder 4 miss while cylinder 3 is still okay, it would also explain unburnt fuel inside cat - ordered replacement along with code reader.

Checking the throttle body butterfly for operation, it opens under throttle (which is weak) but not a huge amount when revving.

 

[DEVOURS]

Whenever I've received new spark plugs, they arrived with the correct gap for my B200. Gap is ~ 0.038 " ..Bosch #BKR6EZB or NGK plugs (different #) as standard dealer replacements..
Others here might change that gap up or down a touch..

I think that all cats are "superhot" under normal operation..and I've never tested the temp to know what the normal range is so I can't add any info on it.

Could you better explain what we are looking at in the 1st photo..with the shiny grayish box with a hole showing..?.

 

[Bnut]

Hello DEVOURS,

The box in the first picture is a close up of coil pack feeding cylinders 3 and 4, the diagram etched into the surface illustrates HT lead configuration (as below pic)

This I believe is what is happening to mine, the rubber exhaust hangers are burning.

Cheers,

Strong burning smell

I have an 8 month old C Class 220 CDi (W204) Sport Auto BlueEFFECIENCY Saloon which I purchased new. It has been back to the dealer on 4 occasions because of a very strong burning rubber smell from the left hand rear side of the car. Mercedes have told me to live with it as they have no...

forums.mercedesclub.org.uk

 

[DEVOURS]

Yes indeed. ..and thanks for explaining and now I get a view of the size of the part from pic #1 above.

If you have those rubber hangers burning,..then you definitely have way too much heat. Probably a sure sign of a serious cat problem and possible blocked..
Not safe to drive anywhere with that burning..

I can't help as I've been problem free with my B.

 

[MB•David]

Fascinating stuff ... not that I ever even consider touching this myself!
Now, where I can fit another camera and make it pop up on the screen automatically?

 

[Bnut]

It tested my little grey cells too, last time I touched a petrol car they had mechanical petrol injection

That said, once you get over the unusual layout and start to identify each part not much has changed. It still uses spark plugs, coils (four of them) along with a set of pistons housed in a water jacket.

I did find it difficult to rev the engine whilst tinkering due to no physical linkage, had to get my neighbour out to help with that one.

DEVOURS, I purchased a set of Bosch mention in your post, these have 0,9mm which is around your measurement of 0.38"

MB David, there's a good overview of cats getting (very) hot due to engine issues, hoping mine is an easy fix with a new coil.

Catalytic Converter Glowing Red Hot

Will keep you guys posted.

 

[Bnut]

The grey cells were wiring again, decided to check part numbers on both coils - if same swap over which I did, no change in fact all cylinders are pretty much the same, just very low power, disconnecting each cylinder in turn doesn't make much difference.

It really smells of petrol fumes from over fuelling, my attention turned to the variable intake which has a vac operated switch to one side - mine has a split boot but also noting attached, i wondered if some kind member could check there's to see if anything (or it's blocked off) is connected?

If the intake is closed shut could explain issues as mentioned.

This video at 4.21 describes the part but cannot hear audio to make out what is is?

4.21 vacuum part

Thanks

Courtesy of doit vehicles

 

[Bnut]

Update

Okay, scrap the request above as vacuum tested the bridge circuit which appears to be working fine.

One thing I did come across were other owners reporting the exact same faults but remain undetected by Star software, the Q & A around this is on page 146 here;

Bert Rowe's A class info

The format is a little unusual but I found the info very helpful.

Following their diagnosis I removed the camshaft sensor which made absolutely no difference at all, this could indicate it's faulty - new one ordered.

Also removed the crankcase sensor breaking off the nut head whist doing so, will attempt to extract that tomorrow. The magnetic coil head was caked in debris which came off fairly easily but ordered a replacement just the same.

Also received scanner today which picked all of the stored faults which were identical to reported above, very impressed with functionality and price, able to read live data too.

Camshaft sensor

Crank sensor

 

[Bnut]

In case you are like me, "how do these things work,..and do they wear out?"

The 'Hall' effect

 

[DEVOURS]

.
Bnut...

Thanks again...very informative !...and Bert Rowe has also been very helpful for us over the past many years..

 

[Bnut]

DEVOURS, thank you.

Over the years I have had a few of these go mainly wheel mounted for ASR/ABS, it crossed my mind these sensors may have a limited life due to the integral fixed magnet?

they do seem to stop working without any physical wear.

 

[Bnut]

From what I have read the magnetic properties are not inexhaustible, although happy to be corrected on this. If this is the case perhaps Hall type sensors should be built into service schedule for periodic replacement.

The sheer number available on ebay suggests this to be the case.

Its also worth mentioning original part OEM numbers seem obsolete, hoping the parts ordered fit and work as per description.

 

[DEVOURS]

.
I've had my B since 2005 and no parts gone bad on it yet..no bulbs..or magnets etc..to report yet....One of these days item #1 will have to get me..but not yet..

The best way to be able to help one with a problem is to have had the experience and share the repair knowledge whenever possible. I've played with the brakes to clean them and that's about it.

..Oil and maintenance..

That's why some mechanics or working tecks can help us in many cases....as we often see now..

 

[Bnut]

That's good to hear!

Bit of a disappointing day my end, fitted both crankshaft sensor and cam sensor, reassembled after cleaning everything then erased codes.

No difference at all, still exactly the same very rich petrol mixture which you can smell from outside, only running on two pots too. Reconnected reader, no codes showing or stored?

Removing the MAP makes little to no difference, can only think it maybe bad injectors but would that not spring a code?

Edit: went out for another try with code reader, this time codes for cylinder misfire on 2 and 4 plus multiple misfires.

It needs to be a fault which allows fuel into the cat/exhaust, perhaps injectors - is it possible to swap them around without removing intake manifold?

Thanks

 

[Bnut]

Managed to remove the fuel rail together with injectors.

Couple of questions, are these injectors serviceable as several guides suggest blockage may have occurred?

Could someone confirm if numer one pot is opposite end to transmission (drivers side UK)

The scan reader reports cylinder miss 2 and 4, I assume that's 2nd from left, and forth - cheers,

 

[DEVOURS]

.
What I did years ago with fuel injectors on my Camry, is to soak them nose down in a very small container and in a strong solution of spray carb cleaner that's recommended when cleaning air flow flaps and external components. I also dripped the solution through the top opening and watched it flow through and exit the spray tip of the injector.. Did it a few times and kept the solution away from the coils or electrical injector parts..not knowing if it would possibly attack the plastics..etc.. Hand wiped the other metal visible injector parts to clean them again with the strong carb cleaner..our Canadian Tire auto parts store has many choices of carb cleaners..so for us here,..it's no brainer.. Can be found everywhere at all auto parts stores.

I had a complete spare engine ..so I could afford to play with some parts and see if all worked for the better...It certainly did..and all of them worked perfectly after that..You could watch the injector and see some grunge flow out with a few repeats.

I can't say if this would help you in your case..and I don't have answers to the other questions..

 

[Bnut]

Thanks DEVOURS,

I hoped by popping out the fuel rail and turning over the engine it would show any defective spray patterns, unfortunately to get the rail out virtually all of the sensors have to be unplugged rendering the engine unstartable.

The other option was to swap 2 and 4 with 1 and 3 to see if codes changed, again the whole engine has to be reassembled to get it started.

As an interim solution I have ordered four second hand injectors which should help diagnose the problem and may even last for 5-10k of miles (they are guaranteed working)..

It's not ideal but I then have a spare set of injectors which can be cleaned and tested, keep you posted.

 

[Bnut]

Well that's me stumped!

Injectors arrived today which looked in good shaped, Mercedes too - fitted and reassembled in a couple of hours, started almost first turn of the key ...and you guessed it no change.

So that's new plugs, crank and cam sensor together with four injectors, will pop out in a bit and check for new codes if any.

Identical codes, P0302 and P0304, cylinder misfire 2,3