Missfire Cylinder 1

[markmifsud]

Hi, today my Engine Check lit up and the car started to drive quite lumpy. I connected my OBD II reader and it showed Cylinder 1 Misfire.

After clearing the errors, I restarted and monitored the real time values
before the error
Fuel Sys1 = CL
Fuel Sys2 = CL

after the error
Fuel Sys1 = OL Fault
Fuel Sys2 = OL Fault

I disconnected the MAF (but a faulty MAF wont affect 1 cylinder?) The scanner confirmed the new errors of the MAF showing a low air volume, and the Rad FAN went on Permenent.

I have cleared the errors many times, and left it with the battery disconnected but the faults show within a min of starting the engine, and its clear its running lumpy.

A few other points need looking at also, the ODB reports engine temps of 82c but the guage in the car shows less than 70c . The MAF was reporting 4.89 g/s is this the correct value?

 

[lynall]

Sounds like you can diy, so remove the effected coil and leads onto another cylinder and see if the fault moves if so coil or leads if not plug fault or wiring.

Use the open end of a 17mm spanner under the metal plug lead caps and they just pop off.

No more than 10 mins tops to do the above

Ps if its a lead dont buy one as i have loads in the garage


Lynall

 

[stevesey]

After clearing the errors, I restarted and monitored the real time values
before the error
Fuel Sys1 = CL
Fuel Sys2 = CL

after the error
Fuel Sys1 = OL Fault
Fuel Sys2 = OL Fault

A few other points need looking at also, the ODB reports engine temps of 82c but the guage in the car shows less than 70c . The MAF was reporting 4.89 g/s is this the correct value?

You may already know but CL = closed loop, OL = open loop. Car goes to open loop control in a number of situations - mainly if the Lamda/O2 sesnor are not up to temp or have failed (after all it's this feedback that closes the loop).

So does your OBDII device show the O2 readings (mV and %)? Would be worth looking at those before and after fault conditions. Although as both fuel systems (1 per bank or the V6) go to OL that would suggest to be a common component rather than the 02 sensors which are separate for each bank.

Edit: Of course as Lynall says a coil pack swap to see of the mis-fire moves with it/the leads is a good test.

 

[markmifsud]

The mv readings are similar for both banks, set 1 are both at .25 and set 2 are both at .756 these figures do not change post error

If its a coil pack, wont i get the error on other cylinders also? as each coil pack servs two different ones ?

 

[lynall]

No each coil pack is in fact 2 coils, 2 leads and 2 plugs feeding one cylinder, you will see when you unbolt the coil and turn it upside down, so thats 12 coils you have

Once cl you should be able to read pre cat and post cat readings on your tool thats a total of 4 readings, iirc mine were between 500 and 650ish both sensors, both banks 6 months ago.

.25 does sound to low.

Firends bora is having some bother and it came up with cylinder 1 and 5 misfire, its a 4 cylinder! but also post cat sensor no output so its probably defaulting to a preset output hence the slight recorded misfire and the reluctance to rev, i left the reader with her and told her to write down codes, then clear them and do the same again, so we can be sure before replacing the sensor.


Lynall

 

[markmifsud]

Well, thanks for your help guys, it looks like its the coil pack after all. I am sure I read that each pack servs 2 cylinders but its deff 1 per cylinder, anyway this is what I found

Well I think i have the answer, unless I have the cylinderr numbers wrong
I swapped over the coil packs from the front two cylinders and the fault has moved to number 4.
So I assume the numbering order is as below
SCREEN
3 6
2 5
1 4
FRONT

Oh and as its a holiday, Merc dearlers are shut

 

[stevesey]

Well, thanks for your help guys, it looks like its the coil pack after all. I am sure I read that each pack servs 2 cylinders but its deff 1 per cylinder, anyway this is what I found

Twin spark engine (e.g. M112 engines) = coil pack per-cylinder.
Single spark engine = coil pack shared between two clyinders.