Very odd ignition problem

[Dale C]

I am chasing a very odd ignition problem. We have a rough idle and miss. After a lot of diag we placed a scope on the plug wires. The left bank 1, 3, 5 all were erratic and dropped out completely at about 2500 rpm. If you switch wires at the coil, flip wires on shared coil (should not matter on wasted spark) the drop out then goes to the right bank. We have swapped coil and module assemblies with the same results. The car drives ok but does seem to be down on power.

Thanks for any help,

 

[WSLN 6]

If you have swapped both with the same problems, I would look into grounding of the module and power feed under load.

 

[2 SLOW]

Try putting on some new spark plug wires.

 

[Dale C]

thanks guys, The power and ground are good, the wires are new Delcos and when switched from bank to bank the problem does not follow the wires

 

[Roger]

Caspers has a coil & ignition tester.

 

[Dale C]

thanks i should have said we alredy tested the module and coils even though i dont have a lot of faith in that type of test on a solid state component. i just cant get my mind around why 2 modules and coilpacks would have the same odd symptom. i am also a little confused as to why the module would drop the trigger on every other pulse it seems that it would be more hit and miss.

 

[RmvBfrFlght]

thanks i should have said we alredy tested the module and coils even though i dont have a lot of faith in that type of test on a solid state component. i just cant get my mind around why 2 modules and coilpacks would have the same odd symptom. i am also a little confused as to why the module would drop the trigger on every other pulse it seems that it would be more hit and miss.

Check the crank sensor and shutter wheel. Also crankshaft end play.

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