e280 misfire 124

[robparker]

My e280 124 has a misfire, it starts fine and idles fine, but with this misfire. I have replaced leads and all coils recently, and when this misfire developed I took the cover off and checked all leads for damage etc, but all seems fine. Any ideas? thanks in advanced

 

[Juddian]

First thing i'd try is to disconnect one coil at a time and see if you can isolate one coil as not firing, therefore 2 cyls should be unaffected by the disconnected coil not working.

If you find a coil down, swap with another, if the same 2 cyls are not firing, you'd better think either wiring loom and or ecu. They arn't cheap, but its not the end of the world either.

This 124 loom problem could have its very own sub forum.

Good luck with it, i bet Bolide will be along with the correct diagnosis soon...doh

 

[kth286]

Rob

When you changed the coils did you also renew the coil extensions down to the three spark plugs ??

If not, do replace them as they contain a resistance wire which gets brittle and breaks contact with the actual plug top connection.

I think they were about £9 each from dealer last time I changed mine which is going strong at 165,000 ish miles.

Also do ensure correct plugs are used - non fancy and non resitive. Buy from dealer - very cheap.

 

[robparker]

Hi Guys, thanks for the replies. I have had the wiring loom replaced a couple of months ago, so that should be ok, and I also renued the coil extentions and have used genuine plugs. To disconnect the coils one at a time to try and identify the one not firing should I just disconnect both ends? thanks alot

 

[Alembic6]

David - many thanks again for your help the other month.

I'm commenting because there is another huge active thread on this subject elsewhere - I posted to it over the last day or two, at length on exactly the same problem. I have a new loom, and the MB dealer man helicoiled a broken coil fixing to ensure the earth was good. My wiring, car same age as yours, was brittle, and obvious missing problem went away for a week or two after it was replaced, but a 'down on power' symptom has now appeared.

My next step is engine earthing strap check, possible over-voltage regulator replacement, and then focus on the ECU, with close ECU inspection, and send off for health check, and re-build. As my other posts state, the ECU is giving an unclearable error message relating to the ECU, and even the dealer is pretty convinced this is the problem. The MB mechanic was a W124 enthusiast too, so I tend to believe them.

I've spent a lot on this car now, so I'm going to have to go all the way - I know it will be worth it because its a such a nice machine ('95 E280 estate, 145k).

cheers tim

 

[Juddian]

Hi Guys, thanks for the replies. I have had the wiring loom replaced a couple of months ago, so that should be ok, and I also renued the coil extentions and have used genuine plugs. To disconnect the coils one at a time to try and identify the one not firing should I just disconnect both ends? thanks alot

IIRC if you disconnect both ends that will do, as the coil has an ingoing lead, then feeds the plug below and the one fed off the outgoing leads, if that makes any sense at all. You could always remove and disconnect each coil in turn, to be sure.
Hopefully if you do this with each coil in turn, it will soon show that disconnecting one of the coils makes no difference at all.
If you then swap for one of the others and the good coil in that position is still not firing, you will have found the bad wiring point, or hopefully just found a duff coil or similar.
Have a good look under the coils for any traces of arcing whilst you've got them out.

It does seem odd that the problem has emerged after the loom was replaced, if it is the ecu they usually give up about the same time, but i suppose it depends on how bad the shorting back was at the time, and all these things can vary.

What does seem constant is that they are a PITA when the go.

If you do find its the ecu, please be very careful where you send it.

 

[Alembic6]

Juddian,
I think there is a general acceptance that ECUs acn get damaged when the wiring loom gets old and begins to breakdown. Dont forget, its not an instant arc one day, its a progressive loss of insulation over time, from say 50megohom down to 100k - so random voltages do get to be emitted.

I've had two quotes, but I'm reticent to say what and who, because these guys and others read these posts, and it can get complicated. However, neither one is in London, where I believe someone got bad service. Also, its all third hand info, which may be slanderous. However, if there is anything I should know, I'm all ears. Can't afford any more hassle, but a close shave looks like a good deal (pun).

 

[robparker]

Ok, well I'll have a go at disconnecting the coils now, I do have a replacement ECU for it somewhere, so if no luck with the coils I will fit that and see if it makes a differance. Loverly car, but this year has given no end of trouble,, headgasket went, replaced that, wiring loom, misfires leading to changing the ignition set, now more misfires...!

 

[Juddian]

Alembic,

I've had 2 ecu's repaired successfully by the people on the IOW.
The first one was where the multi connector had corroded away, and reqd a new connector block soldering in, and obvious testing after, i phoned loads of places and no one else would touch it, parts being the main problem.
Second time with the misfire, i looked around and like many believed some of the stuff thats written on website's, so after phoning to confrim, i sent my ecu to one place who 'tested' it and could find nothing wrong. Sent it to another who pronounced it irrepairable as something that had gone could not be replaced, and would i like the 'scrap' ecu back, yes i'll have it back.
So finally and i kick myself still i sent it to IoW, and paid their admittedly more expensive fee, and the ecu duly came back repaired and trouble free.

http://www.carelect.demon.co.uk/addr.html

So, i learned a valuable lesson there, and i deserve a good kick up the back side for trying to get good service cheaper, already having used them to good effect, it doesn't work, and it could have cost me an awful lot more money than it did.
My experience is that the IoW repairer can do the job, and charges a reasonably expensive fee for doing so, but its guaranteed 2 years and i haven't had to touch either since, so maybe not so expensive really?
I've said elsewhere, take a note of all serial no's etc of your ecu before sending it to some other repairers.

No doubt there are some others who can do just as good a job, and offer a fair work ethic, i don't mean to say that all others will not have the customers best interests at heart, it would be nice if those that have had good service from ecu overhaulers could mention where too.

 

[robparker]

Ok, Well I disconnected the coils one at a time, and it ran alot worse when the front 2 were taken off 1 at a time, and slightly worse with the one nearest the back disconnected, I swapped the back one for a spare I had which made no differance. So.. I guess that means I will try swapping the ECU over for the spare on of those I have one evening this week.

 

[Juddian]

Ok, Well I disconnected the coils one at a time, and it ran alot worse when the front 2 were taken off 1 at a time, and slightly worse with the one nearest the back disconnected, I swapped the back one for a spare I had which made no differance. So.. I guess that means I will try swapping the ECU over for the spare on of those I have one evening this week.

It certainly sounds like it could be the ECU, do you know if the spare one is a good one? At least its only a 20 minute job to try it.
One good thing about having a spare, so long as the car runs reasonably on it, you can send off your original for testing and/or repair and still continue running at least locally.

By the way, if the spare is for the other type of locking/immobiliser, the car will probably run worse than it does with the present one.

If you'd like, those of that have been there could have a worldwide group scream at say midnight, so all together at midnight GMT now all those who have suffered the mercedes misfire woes......:cry:

 

[robparker]

I drove the other car the ECU came from and it was fine, checked on EPC and they match, so hopefully that wil do the job. the 104 engine is the only one that has ever given me trouble from a merc, I had an s320 some time ago that had similar problems, and I probably wont get another one of these again, which is a shame because they are great engines, but just seem very delicate if they start going wrong.. i'll be there at midnight..

 

[robparker]

Ok, Well I just swapped the ECU's over and it started and initially ran the same, but I let it keep idling and after abouta minute it seemed to greatly improve and clear itself, now seems to be running as normal, but with the very occasional one-off misfire, like a little 'burp'.. its idling outside as i type this, going to take for a short test drive now... what do we think then? cured or playing a trick on me?!

 

[Alembic6]

We wait with baited breath, although I would have expected an instant improvement, unless things were a bit oiled or otherwise gummed up from the misfire, and needed soem time to clear. As most of us are already screaming by midnight out here in Lagos, maybe I'll just bang my head into a wall or two...

 

[Alembic6]

I forgot to say, there are loads of old W124s in Africa, millions of them. They were bought (official term) in Europe and driven down, and over the Nigeria border at night, to avoid the huge import taxes. Almost 95% are pre-facelift, up to 1993(?), mostly saloons, but some coupes, and occasional rare cabroilets. Older ones are probably easier to maintain. They have colossal milages - round the clock is the almost the norm. All mostly 220s, not 320s. They are widely known as Vee-boots - pretty obvious really. Even better - they call the later oval headlight E-class - the 'grasshopper'. So now you know.

 

[Juddian]

Well Rob i've got lots of things crossed for you, and i think Alembic you said it, probably oiled up plugs on the 2 that haven't been running, took a few minutes to clean themselves up. Repost when you've got the definate answer please Rob.

The old bill didn't come round after the midnight scream, not that i'm surprised, and i heard no answering calls, so not many of the lesser spotted MB misfires around my neck of the woods.
I've killed loads of magpies, so most songbirds have returned, but that wasn't among them.

Whilst you are in Lagos, Alembic, is it worth enquiring for the hell of it at a MB dealer/specialist about a new ECU in case you need one?
Would be very interesting to see how the price compares to rip off Britain.
Could be easier to find in a scrappie maybe too?

 

[robparker]

well I have been out for a couple of test drives and that problem has definately cleared up now. Still isnt perfect, as it wasnt before this, the odd cough (very occasional) hunting idle.. did find an airleak and fixed that, tried a new MAS.. really cant be bothered anymore, as long as it more or less behaves from now on, that will do! My old 1981 380slc on the other hand, I just turn the key and go, no hassles, no matter how long I havnt driven it for!

 

[Juddian]

Good for you Rob, pleased it worked out.

They really are lovely cars when they're running well, but they can be a lot of trouble too.
I don't think i'd have another of these, unsure TBH whether i'd have another MB at all, lovely though they are.

I'll just wait for the head gasket woes next......

 

[Alembic6]

Rob - great news that the ECU fixed your problem - gives me hope that I can eventually sort my issue.

There's an MB dealer a few miles away from where I work, but getting around isn't that easy, and the phones are iffy today. Anyway, they will only sell the African market gold plated ECU, and it'll have a massive import duty on it. As for finding a scrapyard, you're in it when you touchdown - dead cars everywhere, but the locals are ace at stripping out all the parts and spiriting them away, and I would give an ECU less than 1% change of working.

I guess this thread is pretty well closed now. Has anyone ever produced a list of common late model W124 woes:

- head gasket leaks at about 100k
- wiring loom at about 12 years
- ECU at 150K, or with loom
- OTG often packs up early
- coils often fail and can affect ECU
- wiper stalk switch seems to burn out
- MAF?
- OVPR?
- front wing wheel-arch rust
- Tailgate autoclose (mine still works)
- seatbelt extender plastic gear failure
- lamda sensors
- engine mountings at about 140k

 

[thejap]

Hi, just read through this thread and it reminded me of a similar problem I had with my W210 E240. Misfire, engine light coming on. Diagnostics with MB who wanted to change everything under the bonnet. Came away with a bill for £150 next day same problem, I changed plugs, leads, MAF and a new coil pack. Still no change, but somebody on this forum suggested water in the fuel, so I ran the tank as low as I could my local garage drained the rest and a new fuel filter and has not missed a beat since. I was being told ECU problems etc but it was water in the petrol which took a month to diagnose. So even the experts at MB id'nt find the cause of my woes, but it maybe something to consider. Good luck.