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modifying 740 cpu 700 1989

uid 27's pic
posted by  Art Benstein on  Mon Dec 31 05:57 CST 2001
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last visit: Fri Oct 17 20:10 CST 2014
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Spoofing the ECT? Me too, though on an LH-2.0 car that's my daily driver. The ECT is sourced by 5V through a resistor somewhere up in the 10K range ( I have the exact values at home as it has varied by build ) so the voltage into the A/D converter runs as high as 2.5 on a 17 degree morning like today and down to 100 mV after 5 minutes warm-up.

If you need to (practically) short it out with 400 ohms to start it on a cold day, you have the opposite trouble from mine. Your AMM voltage could be high, forcing it way richer than needed for cold start. I can't give you figures because your ECU/AMM is newer than the one I've looked at.

Talk about annoying -- until I figure out my lean trouble, I have a 10K pot that can be switched to substitute for the ECT which I adjust using a digital panel meter. Makes it difficult to loan the car to anyone.

Wonder what the output voltage is from you AMM? Assume you've checked your fuel pressure regulator -- they have a spring that rusts and breaks causing overpressure, or the diaphragm fails and you bathe your motor in fuel. And then there are reports of 561 ecu cpu chip troubles...
--
Art Benstein near Baltimore






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