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Old 12-14-2018, 06:05 PM   #13
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Join Date: Apr 2010
Location: NC

Originally Posted by cleanflametrap View Post
Yes, you should see the voltage on the black wire kick back and forth between about 0.2 and about 0.8V, switching between lean and rich respectively. The wire needs to be connected. That's how the O2 sensor keeps the average mixture correct.

When it switches below about 0.5V, the ECU is programmed to push more fuel, by lengthening the time the injector valve is open until the O2 reports above about 0.5V, when it will cut back that injector's open time. Like the thermostat in your home. Feedback.

So, if it reports a constant rich signal, something else is not allowing the system to shut down the fuel. The fuel pressure regulator could be faulty, allowing fuel to bypass it through a leak in its diaphragm, or rarely, if it is stuck shut. The air mass meter could be falsely reporting more air than is actually flowing through it, or poor corroded connections might corrupt its message to the ECU. The coolant temperature sensor could be trying to tell the ECU it is minus 40 in the head, or its signal is not being faithfully delivered to the computer.

After some time the ECU has given up trying to get a reaction from the oxygen sensor, and has simply forced a rich mixture to protect the motor, and set the 113 code. Then you'll see it stuck at 0.9V or thereabouts.
Thanks for the info!

I was wondering how one would run rich, i thought the injectors pulsed on at a certain speed and maybe were firing too fast but you helped explain it happens from the injector valve being opened longer. cool now I know.

I have already replaced the coolant temp sensor and I tested the one that came out, I dont believe there was anything wrong with it either.

I removed the fuel rail, swapped in cleaned injectors with new seal and made sure the grounds were good. ive checked the engine bay grounds a few times. I removed the MAF sensor and cleaned it, i done believe theres any problems with the connector there or at the ECU, Ive had it off a couple of times trying to test ohms and continuity of different things.

When I removed the throttle body, i reset the switch but it doesnt make the "click" nearly as loud as the one on my 85 wagon. Could that be a symptom of anything? it clicks but its hard to hear in comparison to my other car....either way ill probably be trying a new (or good used)MAF sensor next. they fuel pressure seemed in spec with only the pumps running, the car running and with the car running and the vacuum hose disconnected. I was also able to blow through the return line to verify it wasnt clogged. It wasnt easy to do but i def heard the gurgling sound at the other end.
85 245 - ipd sport springs and sway bars yoshifab torque rods, kaplhenke bne strut mounts and TAB's. Poly bushings Bilstein tourings. B cam +4. 2.25 exhaust.

93 244 stockish.
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