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ECU is a suspect? 200 1989

Mike,

I believe there is one for sale in the Brickboard classifieds.

Ted has a point about the intake manifold. A chunk can fall out of it causing sudden uneven vacuum. I've seen it. And without extensive troubleshooting, I tend to lean toward more simple explanations like a vacuum leak or leaky FPR.



However, the theory about the cause of the pink label syndrome is not age, but externally caused. The theory has it the signal and power grounds, separately made at the fuel rail mounting screws develop voltage drop in corrosion, and if not there, at the splices just beyond the vinyl sheathing in the engine harness where those two ring terminals lead.



The hybrid circuit inside the ECU was vulnerable to a voltage difference between those two circuit grounds until the hybrid was revised more robust by Bosch and incorporated into the white label -561 and, of course, all the -9xx series then in production.

Those grounds might have a tie-in to your contradiction between ECT code and resistance measurements. You could repeat the check, but use a voltage measurement instead of resistance measurement to verify what the ECU sees from the ECT in operation. Here's a chart relating that voltage to the temperature.




--
Art Benstein near Baltimore

If you tell the truth, you don't have to remember anything.






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