mwoodland

Greetings folks.
Further down the road on the 'Huge Flat Spot' Thread.
Data to date:
Huge midrange bog.
Air Flow Sensor pulled, cleaned w/ alcohol, wiper tension slightly increased.
Air Flow Sensor adjusted to a minimum of 0.9 volts.. would not dial down to 0.6-0.7 range.
Duty Cycle Cold = 50% exactly
Duty Cycle Hot = 8-10%. Once warm, Pin 3 voltage ramps up from 6.6 VDC to 12.3 like it was on rails.
Duty Cycle is non-responsive to unplugging/plugging O2 sensor.
Duty Cycle is unresponsive to mixture adjustment via adjuster 'screw' (allen).
O2 Sensor putting out 0.95 VDC, measured at sensor plug.
Exhaust system has continuity to engine block & to B- on battery.
O2 signal is (apparently) not making it to the control unit (will be checking tonight or tomorrow).
Car is now drivable, now that I've unplugged the EHA connector.
The bog was due to running waaay rich in the midrange. There is still some (barely perceptable) over-rich condition at midrange, i.e. on acceleration from midrange, engine picks up speed slowly, then faster if I back off the gas.

Question 1: Will the engine fire and run with the controller unplugged, so I can verify that the .95 VDC signal is making it to the plug, or should I keep the engine off and just check for continuity, and that the signal is not being shorted to ground, or to the shield.
Question 2: Has anyone encountered broken wires / solder joints, or other 'loss of O2 Signal' situations.
Any BTDTs would be appreciated.
Thanks in advance,
Mark

mleskovar

1. Start the engine and bring it to normal operating temperature, then run the engine above 1200 rpm for two minutes.



2. Backprobe with a high impedance averaging voltmeter multimeter, set to the DC voltage scale, between the oxygen sensor (02S) and battery ground.

3. Verify that the 02S voltage fluctuates rapidly between 0.40-0.60 Volts.

4. If the 02S voltage is stabilized at the middle of the specified range (approximately 0.45-0.55 volts) or if the 02S voltage fluctuates very slowly between the specified range (02S signal crosses 0.5 volts less than 5 times in ten seconds), the 02S may be faulty.

5. If the 02S voltage stabilizes at either end of the special fied range, the ECU is probably not able to compensate for a mechanical problem such as a vacuum leak, faulty pressure regulator or high float level. These types of mechanicalproblems will cause the 02S to sense a constant lean or constant rich mixture. The mechanical problem will first have to be repaired then the 02S test repeated.

6. Pull a vacuum hose located after the throttle plate. Voltage should drop to approximately 0.12 volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a lean mixture condition. Reattach the vacuum hose.

7. Richen the mixture using a propane enrichment tools. Voltage should rise to approximately 0.90 Volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a rech mixture condition.

8. Off the 02S voltage is above or below the specified range, the 02S and/or tho 02S wiring may bo faulty Check the wiring for any breaks, repair as necessary and repeat the test.