Misfire cyl 1

[toylexus]

My daughter has my old 1.4 07 auris. Yesterday went on 3 cylinders. Diagnosis showed misfire on cyl 1.  Changed plugs and put new Delphi coil on that cylinder. Started on 4 cylinders and fault cleared.  Driving down the rd had a constant hesitation but no fault showed. Then onto 3 cylinders. Put on diagnostics and shows misfire on cyl 1. Has she fried the new coil or possible injector? 

[Corolla2004]

My money is on your new Delphi coil is defective.

[Gerg]

I think I would swap the coils between cylinder 1 and any other cylinder, and see if the fault follows the coil or the cylinder.

 

[toylexus]

Thanks for replies . After several days of looking I've discovered that a wire going to the coil on cyl 1 had slightly broken. Run for two days and no fault. Replaced wire as far as I could and hey presto sorted.

[Gerg]

That's useful to know.  Those wires are sometimes a bit tight. 

That's fair enough until the coils are disturbed to change the plugs or something.....

[Konrad C]

Glad you found the broken wire. Could this have been the real fault and the original coil is fine? That is why I would switch coils with one of the other cylinders, to see if the fault follows before splashing out, as suggested by Gerg! 
Last year whilst changing the spark plug (routine service), one of the coil connecters broke at the catch. I replaced that.

 

[Gerg]

Yes, I agree.

The last time I changed the plugs on our Corolla 1.4 VVT-i, I unclipped/unbolted the wiring loom mounts so that some of the coils could stay attached to their connectors, but still allow the plugs to come out, if I remember correctly. 

The stiffness of the connectors and the tightness of the wire bends didn't bode well for longevity, at least when removal for servicing is considered.  Having said that, our Corolla is 20 years old now, with no problems encountered in the wiring department, just the coils slowly failing with age. I've swapped out one of the remaining serviceable coils in the car with a new one, and keep the old working one in the boot as a spare, so only one 'old' coil is still in use now, as two have already failed.  The car has done 135,000 miles.  The original coils were Toyota branded from Germany (Bosch?), the new ones are Interpart (1) and NGK (2), all made in China.

I've got to try to make the car last a little longer - I've already got a new set of plugs for it which it doesn't need for another 4,000 miles.  (Halfords end-of-line-sale, £1.80 a set, a year or two ago - I couldn't leave them on the shelf.... )

[toylexus]

The heat from the engine can make the wires brittle. I was too quick to assume a coil but I'm sure I'll need it at some stage. Thanks everyone for your help. Much appreciated.