159 3.2 V6 Blowing Coil Packs #4 again and again and again

[Colin Edwards]

Hi Mick,
I've often wondered how the ECU "senses" a coil pack is dodgy.  The scan tool seems very powerful and 100% reliable.  Even if a coil pack is iffy, the ECU / scan tool seems to be able to isolate the correct widget.  Does the ECU monitor the current through the primary coil?, or voltage output of the secondary coil?, or measure coil reluctance or inductance?  Does the ECU perform some sort of "health check" prior to the engine firing? 

There are lots of ways to check the health of a coil or transformer.  Just wondering what Bosch have applied in this instance!

Colin.

[bazzbazz]

I've often wondered how the ECU "senses" a coil pack is dodgy. 

White mans magic ?   

[Citroënbender]

Apparently the dodgy ones have an Irish accent. Or at least someone said so recently. 

More seriously I thought the ECU measured power consumption or elapsed time to achieve coil saturation, against stored parameters.

[bazzbazz]

More seriously I thought the ECU measured power consumption or elapsed time to achieve coil saturation, against stored parameters.

     

As Manuel would say " 'Que ?  "

       

(Sorry, I couldn't resist)

[Citroënbender]

Well, do you just look to see if any of the anodes are glowing more or less brightly? 

(Where's the "poking with a stick" smiley when you need it?)

[Colin Edwards]

The resistance of a spare I have is about 0.5 ohm.  No way one of these primary coils can dissipate almost 300W so serious current limiting must be applied.  Active current limiting assumes current measuring and feedback.  Fair chance the ECU is told by the limiting system what the real instantaneous current levels are.  The ECU could also be clever enough to measure the rise time of the primary current.  This measurement would confirm coil inductance and compare against a known value.  If the current level is exceeded or the rise time is less than allowed, a failing or shorted primary coil is detected. 

Methinks much of this system could be embedded in the plug pack - these widgets are not cheap!   If the feedback / current limiting system is not up to the job and allows excessive current to flow through the primary coil it will cook very quickly.  Over tightening of the assembly or rough handling of aged units could damage the current sensor.

[alfagtv100 (Biggus)]

Has anyone experienced repeated coil farts, using genuine (bloody expensive at around $500 a pop) Alfa Romeo coils?

[bazzbazz]

Well the original Alfa units are Bosch, so you could save yourself a fair bit by searching online for just replacement Bosch items, apparently the cardboard box with Alfa stamped on it is VERY expensive. Bosch cardboard on the other hand is a few $100 cheaper.   

[alfagtv100 (Biggus)]

Hi Bazzbazz,

Yes, they are stupid expensive. But that is not the answer.
I popped into a dealer and asked if they had seen the coil #4 issue. This particular one had only come across one case where the owner suffered repeated faults and reluctantly took it to an Alfa dealer. They fitted genuine coils.
Now the mechanic suggested the Alfa ones were;
- yes, very expensive
- possibly made to a spec slightly different to the Bosch equivalent. He freely admitted he was only speculating and could not confirm.

He also admitted he did not know if genuine coils are the answer. However, he did say the customer did not return.

The mechanic did suggest I return next week and ask the workshop manager, who has been running the shop for 15 years.
I will do that on Wednesday and let everyone know.

So, the obvious question.
Has anyone with repeated coil farts, fitted genuine Alfa coils? If so, did they also fail?

[Colin Edwards]

I've had two coils (on different cylinders) fail over the life of the car.   Replaced with coils out of an Alfa Romeo box.  So far those coils have been ok.  Seem to recall the non-Alfa Bosch replacement had a slightly different part # but did look identical!

[bazzbazz]

Colin, how's your memory, did the original Alfa part have Bosch or NGK on them anywhere? Remember folks, who do you think make the coils for Alfa.   

[alfagtv100 (Biggus)]

Colin's answer part answers the question.
What would help further is evidence of genuine replacement Alfa (no matter who actually makes them) coils blowing prematurely.

[Colin Edwards]

Hi Bazzbazz,

All the "original" Alfa Romeo coils I have seen are a Bosch product.

[alfagtv100 (Biggus)]

3rd time lucky.
Has anyone replaced a blown coil with a genuine Alfa Romeo coil and had that coil blow?

[Citroënbender]

On a 147 TS, yes, twice!