Tom:

Something wrong with the EHA current in startup state would indicate a bad computer, it's not getting any data (rpm, etc) from the engine. Unless a bad temp sensor or grounded or open wire can do this (stevebfl or someone else with far more expertise will have to tell you, I don't know), the ECU is sick. If it is, won't matter what else is going on, the mixture will wander around.

I assume that you have gotten the ignition system in tip-top shape as well -- misfire will cause black sparkplugs, too! Since you've been chasing an idle problem, I'd guess you've fixed this.

There have been several posts about curing rough idle problems with new injectors -- if they are not delivering the same amount of fuel each, the mixture will be off for at least one of them (some rich, some lean, etc) and you will get loping idle and constant EHA current variations as the ECU attempts to get the O2 correct -- since some cylinders are richer than others, too much O2 gets by on the lean ones, so the ECU richens up the mix to get rid of theO2, the rich cylinders get richer and the O2 drops too far, the ECU leans the mix back out, the lean cylinders go too lean and misfire, the O2 goes way up, and the cycle repeats. The missfire makes the engine run rough, and the rich cylinders end up with soot on the sparkplugs. the soot will burn off at highway speeds and re-appear at idle.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!