1992 400E-101,000 odd miles I am getting codes 2,7, and 17. I have changed out spark plug wires(Beru), spark plugs(Bosch Super), ignition cap, rotor, and o2 sensor already. I have a miss during idle cold and hot. I have quadrupled checked over everyting I repaired .I also checed for leaks in vacuum hose connections. I have some black residue around the mass air flow but, if it was leaking. I think a code would pop up showing this is the problem. When, I checked the harnees now, I get more codes. So, I suspect it is the wiring harness.

Has anyone does this as a DIY? Do you have to disconnect the battery? I opened up the sleeving and sure enough the insulation is flaking like the pictures that are shown on this website.