Misfire Mil Need Help Diagnosing

[hairyspiderbaby]

Hello I have a 2004 Yaris 1.3 VVti which has developed a misfire although more pronounced when engine is warm.

I have read the fault codes and they were:

*P0100 Mass Air Flow (MAF) Circuit Malfunction

*P0101 Mass Air Flow (MAF) Circuit Range/Performance Problem

P0300 Random/multiple misfire detected

P0304 Cylinder 4 misfire detected.

I replaced air filter, mass air flow sensor and spark plugs and this has got rid of the first two faults(*)

Any ideas how to fix the remaining problem, this misfire is really bad when warm and driving in town?

[Geoff Peace]

Hello I have a 2004 Yaris 1.3 VVti which has developed a misfire although more pronounced when engine is warm.

I have read the fault codes and they were:

*P0100 Mass Air Flow (MAF) Circuit Malfunction

*P0101 Mass Air Flow (MAF) Circuit Range/Performance Problem

P0300 Random/multiple misfire detected

P0304 Cylinder 4 misfire detected.

I replaced air filter, mass air flow sensor and spark plugs and this has got rid of the first two faults(*)

Any ideas how to fix the remaining problem, this misfire is really bad when warm and driving in town?

It would point to a faulty coilpack on No. 4 cylinder. Change the coilpack with one from another cylinder and see if the fault code changes to confirm. Inspect the air induction path carefully for any signs of an airleak caused by a split in the airbox, inlet manifold etc. they are all plastic.

Regards Geoff Peace.

[hairyspiderbaby]

Thanks Geoff your solution was spot on,it was indeed a faulty coil pack and breaks only when the coil gets hot!!

New coil pack and the car is running fine!