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-   -   Changed ONE coil (Cylinder 5)...BUT... (https://forum.a8parts.co.uk/showthread.php?t=14901)

DailyMike 14th April 2019 03:22 PM

Changed ONE coil (Cylinder 5)...BUT...
 
...since I changed the Cylinder 5 coil pack yesterday, it has eliminated the multiple cylinder misfires across BOTH banks!

Logically, I believe that they would be independently wired, but the frequent (several times daily), multiple cylinder misfire codes for the last few days have DISKAPPEARED and the car's running sweet as a nut!

So...are the coil packs somehow linked?

DailyMike.

ainarssems 14th April 2019 09:06 PM

Quote:

Originally Posted by DailyMike (Post 149711)
...since I changed the Cylinder 5 coil pack yesterday, it has eliminated the multiple cylinder misfires across BOTH banks!

Logically, I believe that they would be independently wired, but the frequent (several times daily), multiple cylinder misfire codes for the last few days have DISKAPPEARED and the car's running sweet as a nut!

So...are the coil packs somehow linked?

DailyMike.

I am not 100% sure about this but I have definitely witnessed the same behaviour. I think what happens is after certain number on misfires ECU cuts fuel for the misfiring cylinder to stop unburned fuel going in exhaust and damaging cat, that means only air passes through that cylinder, lambda probe reads it as too lean mixture and increases fuel for remaining cylinders, if it gets too rich it will cause misfires on other cylinders. Now again I am not sure but I think it would be fair to assume that ECU is smart enough not to do this and just switch off lambda monitoring when it cuts fuel for 1 cylinder in which case it runs only on MAF readings and if the MAF is a bit out or if injectors are either worn letting more fuel through or partially clogged letting less fuel through then mixture will be wrong and may cause misfires.

DailyMike 14th April 2019 09:26 PM

Quote:

Originally Posted by ainarssems (Post 149719)
I am not 100% sure about this but I have definitely witnessed the same behaviour. I think what happens is after certain number on misfires ECU cuts fuel for the misfiring cylinder to stop unburned fuel going in exhaust and damaging cat, that means only air passes through that cylinder, lambda probe reads it as too lean mixture and increases fuel for remaining cylinders, if it gets too rich it will cause misfires on other cylinders. Now again I am not sure but I think it would be fair to assume that ECU is smart enough not to do this and just switch off lambda monitoring when it cuts fuel for 1 cylinder in which case it runs only on MAF readings and if the MAF is a bit out or if injectors are either worn letting more fuel through or partially clogged letting less fuel through then mixture will be wrong and may cause misfires.


Interesting...thanks for the input!

I should likely have mentioned that the car is run solely on LPG once it's warmed up to the required temp...about 60C I believe. At that point, I believe the Prinz LPG ECU would be in control?

Mike.
PS: Car STILL running sweet as a nut!
I'll be doing about 400 miles tomorrow with my grandkids, so that'll be a good test...

ainarssems 14th April 2019 09:42 PM

LPG ECU normally is not standalone unit but a piggy-back from the main ECU, main ECU calls all the shots if it does not tell injector to open LPG ECU will not open it.

DailyMike 15th April 2019 07:28 AM

Quote:

Originally Posted by ainarssems (Post 149727)
LPG ECU normally is not standalone unit but a piggy-back from the main ECU, main ECU calls all the shots if it does not tell injector to open LPG ECU will not open it.

Good to know and sooooo reassuring that there's such a wealth of knowledge on the forum!

100 miles into today's trip and running beautifully!

DailyMike.

27litres 16th April 2019 11:06 AM

Quote:

Originally Posted by ainarssems (Post 149727)
LPG ECU normally is not standalone unit but a piggy-back from the main ECU, main ECU calls all the shots if it does not tell injector to open LPG ECU will not open it.

I would second this.
My understanding of LPG ECUs is that they take the injector pulse signal from the car ECU and use that as its own injection trigger. The difference is that the LPG ECU will deliver a proportionately longer injection pulse as the engine requires more LPG than petrol. And of course it will be responsible for interrupting the signal to the petrol injector.

DailyMike 16th April 2019 08:00 PM

Quote:

Originally Posted by 27litres (Post 149778)
I would second this.
My understanding of LPG ECUs is that they take the injector pulse signal from the car ECU and use that as its own injection trigger. The difference is that the LPG ECU will deliver a proportionately longer injection pulse as the engine requires more LPG than petrol. And of course it will be responsible for interrupting the signal to the petrol injector.

Cheers, Marty!

I'm just totally chuffed that the problems have now been sorted so easily!

DailyMike


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