W124 Misfire - The saga continues

[GP801]

1995 E280 S124 now at 132,000. This car has recurrent problems with a misfire. I have been through the old paperwork from the previous owner and I have had the car for just under 1 year. The story so far:
April 2007 at 107,000 Ignition coil x1
December 2007 at 116,000 Ignition coil x1. Repairs to wiring loom
September 2008 at 118,000 New wiring loom, Ignition coil x2, new plugs
Jan 2010 at 124,000 ignition coil x1 + HT lead
June 2010 at 128,000 Misfire but cured itself after 45 mins
August 2010 at 129,000 Misfire cured itself after 2 hours
November 2010 at 130,000 HT lead, plug cap and new plugs
January 2011 at 131,000 Ignition coil x1

All the above were to try and cure a misfire and seemed to work for a short time. All parts genuine MB. It is now back with the dealer again for the same problem. The guy working on it has 40 years MB experience so ought to understand the 124. I am now getting rather disheartened. The car is immaculate with no rust so I really dont want to give up. It seems as if we are treating symptoms rather than cause and that there is probably something causing all this to happen. Could it be the ECU? Any other ideas. All suggestions gratefully received
Nigel

 

[Dave Lewis]

Since you have replaced all the ignition components downstream of the ECU, and been through 6 coils, it's well worth having the ECU checked, since there was a repair to the loom before replacement which could have caused some damage. Also make sure the dealer has fitted the correct spark plugs - in my experience plugs with the wrong heat range can cause problems. Presumably the dealer has read the fault codes and ruled out fuel system faults?

 

[jonnyboy]

You might want to read through my tale of woe with a 280 w124 too.....

 

[grober]

Try some NGK BCP6E plugs if NGK are good enough for the SLS_____? http://www.ngkntk.co.uk/working/FileLib/NGKCarcat2010.pdf Its worth taking out the plugs and looking at their appearance since this can often give a clue to what's going on. The plug extenders from the coil or on the extension lead to the "other plug " often give problems so make sure they have all been renewed. Other possibilities could be a manifold air leak leading to a weak mixture--- the valve or associated pipework to the fuel evaporation charcoal filter often causes problems. Other possibilities could be with the 2 major mixture sensors -either the MAFF or the Lambda Sensor[ or its heater] or even the engine coolant sensor for the injection system. Sometimes you need to go back to basics-- what are the spark plugs telling you? The best diagnostic tool for these [ pre fault code] older cars imho is one of the older fashioned oscilloscope engine analysers- and someone who knows how to interpret the results.

 

[GP801]

Thanks for all the ideas. Just had a call from the dealer. The ECU is shot! Estimate approx £1400 + vat !! Fortunately have an aftermarket warranty that is going to cover most of this. I think it will end up costing me around £400 so not too disastrous. To top it all the central heating boiler and sky box both died yesterday aswell. At least thats my 3 out of the way I hope.

 

[grober]

I take it that's for a Brand spanking new MB ECU ?? BBA reman will do exchange repairs [CHEAPER] on these - usually its the ignition output transistors that go on them due to heatsink failure or HT COIL spiking! Electronic fuel injection engine management units.
They offer a warranty on these exchange units but they usually repair your original unit so you have to send it to them for repair.

this guy charges a mere £120 plus vat! and is well spoken of on the other forum http://www.the-ecu-doctor.co.uk/
as are these guys

http://www.ecuclinic.com/

http://www.ecu-repairs.com/

 

[GP801]

I take it that's for a Brand spanking new MB ECU ?? BBA reman will do exchange repairs [CHEAPER] on these - usually its the ignition output transistors that go on them due to heatsink failure or HT COIL spiking! Electronic fuel injection engine management units.
They offer a warranty on these exchange units but they usually repair your original unit so you have to send it to them for repair.

Yes. Genuine new MB part from Germany. I did think about a repair but bearing in mind the net cost with the warranty contribution I am inclined to go for the new one.

 

[grober]

Yes. Genuine new MB part from Germany. I did think about a repair but bearing in mind the net cost with the warranty contribution I am inclined to go for the new one.

FAIR ENOUGH its your car and if the cost is covered by warranty. By the way if you are paying for a new one outright I would ask for my old one back.- you are entitled! and have a go at repairing it yourself or with the help of a electronics tech friend. http://www.mbclub.co.uk/forums/general-discussion/102590-ecu-ignition-output-transistors.html

 

[ched999uk]

GP801: I assume that the garage will give you a written guarantee that its the ecu causing your misfire? I know you and previous owner have had lots changed but a £1400 replacement ecu is a lot of money if the garage are not sure. Most electronic units are not returnable if they have been used. i.e. if the replacement ecu doesn't cure the issue you wont be able to get your money back - but the garage still makes their profit!!!!!!

If you have to contribute £400 even with the warantee I would risk £120 +vat and delivery on a repair. At least if the repair doesn't cure you have only wasted £155 not £400. The first link provided by grober even provide a 12 month warranty, so the same as a £1400 new one!!!

Which ever option you go for best of luck and let us know how you get on.

 

[kth286]

which garage is the car with?

we can likely tell you their reputation and if they are good with that model car.

cause for me it does not look good - that should have been put to bed ages ago with all problems solved - they are such a good car to work on in a diagnostic sense.

 

[GP801]

which garage is the car with?

we can likely tell you their reputation and if they are good with that model car.

cause for me it does not look good - that should have been put to bed ages ago with all problems solved - they are such a good car to work on in a diagnostic sense.

Most of the previous work - loom, coil packs was done by Etoile tuning, Le Chesnay France. Mercedes, AMG, Brabus and Kleeman approved and also do a lot of classic work - 107s, even original gullwings. As far as I can tell they know their stuff.
Currently with MB Gatwick - part of Lookers group. They have a guy with 40yrs MB experience who seems to know his way around a 124. In fact their driver told me they still run one for deliveries etc. To be fair to them they only did the last coil pack after the car came back from Italy and it did seem to cure the problem for a time. Part of the problem is the intermittent nature of it. Coming back from Italy last time it misfired for about 10km and ran perfectly the rest of the time. They are absolutely certain the ECU is the problem. New one comes with a 2 year warranty. They have looked after our MBs for the past 10 years and do seem helpful and knowledgeable. Also open to a sensible discussion with a slightly knowledgeable owner. They are also doing a very good labour rate.
Car is almost concourse, rust free, dinitrolled so I plan to keep it as long as I can afford to fuel it. It is ideal for running up/down to Italy fully loaded.

 

[ched999uk]

GP801: Sounds like you know the garage well and they know you. A 2 year warranty and your trust in the garage sound great.

Hopefully this will be the end to your problem.

 

[GP801]

New ECU due in 2-3 days from Germany - will let you know what transpires

 

[GP801]

Just a quick update. We are now the proud owners of a brand new ECU. So far car is running better than ever. They gave me the old one back without prompting. Now just got to get the money out of the warranty company but they have agreed to pay so hopefully should not be a problem. Lets hope this is the end of the saga. Thanks to everyone for their ideas and help.