On the 2.1, the oxygen sensor grounds via pin 19 of the ECU. From this pin, a brown wire runs through the main wiring harness and emerges from the same bundle as the distributor wiring. It normally connects to the left head but often has been moved in older vanagons. Many a vanagon owner has swapped in parts trying to diagnose poor performance when the cause was a loose or missing pin 19 ground. If you have a digitool, try disconnecting this wire and watch the oxygen sensor readings (and performance) go haywire. I don't believe a rusty exhaust system will affect the system at all. Another point to be aware of is that the big green wire that carries the oxygen sensor current between the sensor and the ECU is coaxial. It is a central wire, a layer of insulation, a grounded sheath, then another layer of insulation. If the central wire ever makes contact with the grounded sheath, the circuit is grounded out and the van will run rich forever till the problem is corrected. Often a mechanic crimps a new connector onto the end of this wire, gets the grounded sheath under the connector and then spends hours trying to figure out why the engine won't run. Hope this info helps someone. I learned some of it the hard way. Bill St. Louis www.geocities.com/wdummitt |
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