A while back this bus came in to the shop missing and spitting raw gas. The bus has 178000 miles on her with all original equipment like spark plugs. So we figured must be spark plugs and wires since they were original. Changed them out and showed number 8 had a really bad miss. Ran a compression check and it was below 100 psi. Thought was maybe bad injector washing the rings down with gas. Changed injector ran engine again. Still miss in number 8 but compression jumped to 125.Thought maybe bad coil. So we moved all the ignition parts to number 6 ( coil, spark plug and wire) to see if it followed. It did not. Could we have a bad injector again? Number 5 and 6 have a slight miss but aren't dead like number 8. What could I be missing? Thanks
swap the injector plug in to another injector and see if it follows, to eliminate injector or harness do these engines have cam issues , lifter issues the 4.8 vortex have knock sensor issues cause misfire codes vortex5300 has issues with cracked heads does it have the AFN lifter ( does it drop cylinders for fuel eco?)
OEM trained in wiring and all engine platforms for over 20 years
check the valve springs have had to replace a few valve srings on higher mileage buses they usually break u will notice it if u take valve cover off that could be the cause of your compression jumping aroung they are very simple to change in the bus
I am wondering about the valve spring. I took another look today. I took the plug wire off number 8 and ran the bus for a little bit. Got a really strong spark from the coil. Then removed the plug to see if the plug was wet with gas. Dry as a bone. So either the new injector is bad or nothing is turning the injector on?