Engine Warning Light - car misfires

[Keith1906]

having re-occuring issue with engine warning light - car starts to misfire always on same cylinder (No6). Changed spark packs, HT leads, swopped injectors - same problem still on no 6. Is this an ECU fault and if so what is it and what is the solution? Thanks. :-?

 

[Bolide]

So far all we know is that your car has at least six cylinders and runs on petrol

Some more information would be useful!

Nick Froome
www.w124.co.uk

 

[Keith1906]

Is it an ECU fault

Thanks for your observations - other than - the warning ight comes on - the car misfires - we tried some remedies - does anyone know of any ECU faults which may cause this? What information do you want?....

 

[television]

We need to know the model of the car, as there are hundreds of different models

 

[Keith1906]

Model of C 240

Mercedes C240 (W203), Year 2002, Chassis No 203.061, Engine No 112.912 - anything else like the actual VIN or anything? - Thanks

 

[eric242340]

Mercedes C240 (W203), Year 2002, Chassis No 203.061, Engine No 112.912 - anything else like the actual VIN or anything? - Thanks

I hate to be the pain in the neck, but what is the year and mileage? and when was it last serviced? I think this will help others to help you.

 

[television]

I hate to be the pain in the neck, but what is the year and mileage? and when was it last serviced? I think this will help others to help you.

Asking a question like that when its all there and more you are:roll: :roll:

 

[television]

You will need to monitor the signal going into the coil pack to see if it is receiving the voltage from the ECU I cant see any other way, best done by monitoring the signal on a scope

 

[Keith1906]

Engine warning light and ECU

So!!! To recap - I am having re-occuring issues with engine warning light - car starts to misfire always on same cylinder (No6). Changed spark packs, HT leads, swopped injectors - same problem - still on no 6.
Car details are: Mercedes C240 (W203), Year 2002, Chassis No 203.061, Engine No 112.912, last serviced in Aug 06, milage 46K.
Is this an ECU fault and if so what is it and what is the solution?
Thanks to Television for suggestion.

 

[television]

So!!! To recap - I am having re-occuring issues with engine warning light - car starts to misfire always on same cylinder (No6). Changed spark packs, HT leads, swopped injectors - same problem - still on no 6.
Car details are: Mercedes C240 (W203), Year 2002, Chassis No 203.061, Engine No 112.912, last serviced in Aug 06, milage 46K.
Is this an ECU fault and if so what is it and what is the solution?
Thanks to Television for suggestion.

The only way is to view the output from the ECU is on an analyzer where the fault can be seen in real time, if the engine is OK some of the time, this bring the fault down to a bad connection from the ecu to the coil pack or a dry soldered join within the ECU. You could put a simple meter from the input to the coil pack and the output pin that drives number 6 and move the wires etc whilst checking for continuity.
Electronic components virtually never behave intermittent, they either work or they do not. You could unplug the ECU and clean all of the pins with contact cleaner, Does the fault always accure are a certain time running,or is it random

 

[Keith1906]

The fault is completely random. Doesn't matter how hot or cold engine is. Short or long journey.

 

[television]

The fault is completely random. Doesn't matter how hot or cold engine is. Short or long journey.

OK that cuts it down to, poor connection from ECU to coil pack or bad connection inside the ECU, you could try giving the ECU a clout with the handle of a screwdriver to see if it will start or stop the fault

 

[Keith1906]

OK. That sounds like an age old remedy but will try. Am at garage 2morow.

 

[BlackC55]

Try replacing the coil pack or swap it with another cylinder to see if it "jumps" to that one.

Coil packs are a very common cause for missfire's