So the trailing coil back on my friends car only half of it is firing. So Is it not grounded right or is possible for just half to work?

 

Yes it is possible for only one of the two trailing coils to be working.

And grounding the frame is not needed for the coil to fire. The ECU sends ground to the ignitor and that fires the coil.

 

thank you so much. ill replace the coil.

 

so heis been driving the car for a while like this. So how baldy did he mess the engine up?

 

It's the ignitor assy that HAS to be bolted to the frame for either coil to work. At least one of the two inboard nuts/studs has to be installed. The outboard stud/nut that matters not since its a rubber insulator.
IF one coils fires then the ignitor assy is grounded to the frame.

 

Almost forgot. The Select signal from the ECU going from 0 to 5vdc causes one of the trail coils to fire and the select signal going from 5vdc to 0 causes the other coil to fire. The ignitor supplys the gnd to the coil.

 

thxs for the help

 

My Trailing coil went bad in exactly the same Fashion,Half Firing.So Yes,it is Possible for One side to go bad and the other side be good.
I tested it by Pulling the Spark plug wires at the coil.Only one showed Spark.The other one,showed absolutely Nothing.