Misfire

[toylexus]

Hi all. Misfire showing on my 07 1.4 auris, showing misfire on cylinder 4. Is num 4 the one closest to gearbox or the other end?.

Many thanks

[TonyHSD]

Yes, it’s closest to the gearbox. 
Could be anything, from a bad spark plug, coil, or coolant or fuel leak. 
 

[toylexus]

Thanks Tony. I'll try the coil pack first, had new plugs in about 4 mths ago.

[solero]

Were the replacement plugs genuine originals?

Fake plugs can cause coil pack failures due to the differing resistance.

[flash22]

don't replace parts just swap them !!

swap coils 3 and 4 if the misfire moves you know it is a coil pull the plugs and check the gap and colour - as above lots of fake plugs on eBay stick with oem or Denso

[solero]

If you have a multimeter handy, try measuring the resistance of each of the spark plugs (tip to connector).

Keep the readings in cylinder order. If you still have the original plugs, repeat the same and compare.

If you suspect a coil pack, another useful test is to compare the resistance readings between each coil pack connector terminal (on the disconnected coil pack)l. Eg for 3 pin coill pack, 6 readings:

1-2, 2-1:

1-3, 3-1:

2-3, 3-2:

Compare readings keeping them in cylinder order.

I also measure resistance of each of the injectors.

Hopefully your misfire wont be due to poor compression.

 

[solero]

3 hours ago, solero said:

If you have a multimeter handy, try measuring the resistance of each of the spark plugs (tip to connector).

Keep the readings in cylinder order. If you still have the original plugs, repeat the same and compare.

If you suspect a coil pack, another useful test is to compare the resistance readings between each coil pack connector terminal (on the disconnected coil pack)l. Eg for 3 pin coill pack, 6 readings:

1-2, 2-1:

1-3, 3-1:

2-3, 3-2:

Compare readings keeping them in cylinder order.

I also measure resistance of each of the injectors.

Hopefully your misfire wont be due to poor compression.

 

Sorry i forgot to add the spark plug output on the coil pack as the 4th terminal connection for readings.

[toylexus]

Thanks solero, that's brilliant.  Turned out it was indeed the coil pack and yes the plugs were genuine replacement. 

Thanks everyone for the input. 

Much appreciated.