Diagnosing Codes

[S Marks]

This morning, my '99 DII starting to idle very rough and stumble upon initial acceleration. On the way home, it was consistently getting worse and the SES light appeared. The codes it is throwing are as follows:

P1300--Ignition System or Misfire
P0304--Cylinder 4 Misfire
P0307--Cylinder 7 Misfire
P0300--Multiple Cylinder Misfires

Of course, my warranty just expired. It has 62K miles. The heads were just replaced. Wires and plugs replaced about 4-5K miles ago. MAF was replaced several months ago. Since the archives haven't been transferred over, search does not turn up much.

Thanks in advance,
Spencer

 

[andrewv]

What plugs did you use?

 

[S Marks]

Just the recommended Champion plugs according to the manual...don't recall the exact model.

 

[Joey]

Could be a bad coil pack?

The electronic ignition system uses four double ended coils. They are mounted on a bracket fitted to the rear of the engine. The circuit to each coil is completed by switching within the ECM, allowing each coil to charge up and fire. Sparks are produced in two cylinders simultaneously, one on compression stroke, the other on exhaust stroke. Note that coil 1 feeds cylinders 1 and 6, coil 2 feeds cylinders 5 and 8, coil 3 feeds cylinders 4 and 7, and coil 4 feeds cylinders 2 and 3. Due to the ease of combustion in the cylinder on the compression stroke, more energy is dissipated in that cylinder. Coil failure will result in a lack of sparks and misfire in the affected cylinders. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.

 

[S Marks]

Good info Joey

Is the coil pack one unit or four? I guess the intake plenum must come off to access and change it out?

TIA,
Spencer