Injector #4
 

I have a 1998 base with 2.2 misfiring because the #4 injector is on constant. I've tried changing computer, took pin out of harness and soldered a new wire on, changed the injector, and checked other wires. Nothing is working, anyone have any other ideas?

not sure what "checked over the wires" consists of so....
maybe the #4 injector return wiring is shorted to grd.
the pcm turns on the injector by providing grd.
key off- disconnect the injector connector
test for short to grd with an ohmeter....one probe on the battery negative the other on the injector blue/black wire. should be open...any ohm reading is short to grd

Checked over other wires meaning I took all the wires going to that harness out of plastic surround and seen if any others were broke since the blue wire #75 on computer which goes to #4 injector was broke. I replaced that whole wire from pin to injector. Getting a niod tester tomorrow to make sure it is still on constant tomorrow after I replaced wire today.

closer look at the diagram shows both number 1 and 4 injector controled by c2 pin 75 and injectors #3 &4 controlled by c2 pin 76. So if its only #4 injector is open all the time it can't be a grd control issue as it should effect both 1 & 4

Ok but #1 is fine. And I've replaced the injector itself and also the plug on it. I've never had such an issue with making engines run. It ran good before then just started it one day ended up with no power at all to #4 so replaced plug on injector, then injector itself, then found broke wire #75 put wire together got power but then constant. Then changed computer still no change, found wire was burnt and brittle all way back to pin so soldered a new one on today and put pin back in harness, still no change. And that's where I'm at

what if you disconnected the new wire you ran and jumpered the number 4 grd wire to the number 1 grd wire. the on all the time started after this new wire was run? are you sure the new wire is in the correct connector and pin location?