Where would we be without wires? Automobiles wouldn't work would they? About ten years ago the term drive by wire came up with reference to the accelerator pedal and the connection to the engine. Instead of mechanical linkage sensors and motors started being substituted so as you pressed on the pedal an onboard computer would see the movement and track/move the throttle plate accordingly.Thus the term drive by wire. But today I am also talking about a different scenario. When you come right down to it all cars today and yesterday are drive by wire. Let me prove it.
A 1996 Chevrolet Suburban came into the R\A Automotive this week. Misfire codes, dead cylinders and an extreme power loss complaint. Service engine light or the MIL (Malfunction Indicator Lamp) was stuck on, blazing away, screaming "I'm broken, help!" A small pile of parts had been previously installed in an attempt to cure the problem so we had our work cut out for us. After the usual diagnosis; scan codes, scope ignition, mechanical cranking and running compression tests we turned our attention to the fuel injector. This vehicle has a CPI or central injection unit sometimes referred to as a spider assembly. Looks like a spider too, see.
After removing the upper intake plenum we inspected the previously installed new spider and tested each injector for volume and pressure drop. 2 cylinders; the 2 we saw the power loss on tested out of range by about 8% when compared to the rest of the unit. But it was still not enough to cause a completely dead cylinder and extreme loss of power. Our problem was elsewhere. After reassembly we went back over our notes and thoughts. There is where the A-Ha moment came. Why was the wiring harness laying across the top of the engine looking like it was partially rubbed through? On raising the harness you could see copper bits and specks. Opening up the loom we found this.
Besides the broken wire (which had been hanging on by 3 strands until we started annoying it) , 2 others were melted together. When we sorted them out the broken wire fed the injector for #6 cylinder; the other wires for injectors on that bank. After repairing the harness and broken wires the truck ran as it was supposed to.
Drive by wire...we would be lost without it.
See you on radio
Ron Ananian
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