How to find a bad ignition coil

[thexav]

The engine is misfiring and having checked everything else and read fault codes I'm getting a bad ignition coil.

How do you work out which one is bad as there is one for every cylinder and the car (Audi S6 has 5 to choose from!)

 

[HDi fun]

Coil per cylinder is fairly common. OBDII should give you the exact cylinder number.

 

[obi_waynne]

Trial and error is the only option if there is no fault code specific enough.

Get a new one, try it in each slot until it runs smoothly. The problem is if there are more than one at fault.

When one goes it usually means the others are 6 months behind so I'd bite the bullet and replace them all.

Bear in mind it could actually be a bad lead rather than a bad coil if these are not all in one moulded units.

 

[HDi fun]

I think with two or more faulty coils you'd have extreme difficulty starting the engine at all.

A DVM is invaluable. Just pull off all the coils, check primary and secondary coils for continuity. Also check that primary hasn't shorted to secondary.

 

[T9 man]

I will have to find out from the garage as I know for a fact that coil failure does not bring up an engine check light in my car.

 

[HDi fun]

That's probably because you've modified it to the point that the ECU no longer actually recognises it as an internal combustion engine at all

 

[TCJBOLDIE]

^^^^^^

 

[herb]

Get yourself a odb Bluetooth and purchase the tourqe app it shows which cylinder isn't firing correctly

 

[HDi fun]

Get yourself a odb Bluetooth and purchase the tourqe app it shows which cylinder isn't firing correctly

Already been there on 28th Feb. Depends how granular the OBDII data itself is. The ELM Bluetooth and Torque App can't divulge what isn't there.