civic_rider
Junior Member
Dec 30 2003
quote:
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OK here's the status and what I've learned.
What I've learned;
1. With the EACV totally closed and the motor cold, the cold idle valve lets to much air through, the engine hunts for about 1 minute, until the valve starts to close, then it just runs fast (as it should). This is an easy fix, we just cut down on the amount of airflow through that valve, with a brass gasket, restricting the air flow.
2. The ECU outputs a ground signal to the EACV (steady ground, no pulsing) until well after the cold idle valve has closed. This means you have full bypass of the throttle, resulting in much more air than the engine needs. According to the Honda manual, during warm-up the ECU should be opening the valve to allow for faster cold idling. After the ECU shuts the EACV down, the engine drops to slow idle, (450 RPM). There is no further activation of the EACV. The ECU should (per the manual) actually operate the EACV enough to increase warm idle by 300 RPM, it isn't doing this
I monitored this with an oscilloscope, the control was definitely a hard ground with NO pulses. The valve was fully open, max air bypass, until well after the cold idle valve closed.
3. Using my pulse width modulator tester, that I just built, and driving the EACV, I can change the idle to what ever I want, by controlling the air through the EACV, from full open to full closed. This test indicates that the EACV is definitely operating. Also of note is the noise generated by this solenoid valve oscillating on and off, you can definitely hear the operational action.
4. Still getting the EACV fault code 14
5. The Engine still hunts at about 1500 RPM.
6. O2 sensor output;
a; rev engine to 2000RPM, then drop quickly to idle. O2 output goes from .9 volts to about .3 volts, then creeps back up to .9 volts. (O2 test from Honda manual)
b; at idle (approx 750 RPM), O2 output crosses .5 volt level about 7 times in 10 seconds. Engine does not hunt.
c; at approx 2500 RPM, O2 voltage crosses .5 volt level, over 20 times in 10 seconds. Engine does not hunt.
d; at approx 1500 RPM, engine is hunting, O2 output remains at about .3 volts. When RPM is increased, see "c" above.
7. Throttle position sensor varies between .5 volts and 4.5 volts (per service manual)
8. MAP sensor, Ignition ON, car not running, output is 2.9 volts. Engine running at idle, output is .98 volts (varies with engine RPM)
9. Coolant temperature sensor, hot engine, approx 250 ohms.
10. Dist sensors, TDC,Crank,and Cylinder pos. all have signal outputs, measured with an oscilloscope.
11. Vehicle NOT equipped with a ELD (Electric Load Detector), well at least there is no GRN/RED wire on connector D10 of the ECU
12. Timing set per red mark on crank pulley
13. All sensor measurements take at the ECU.
14. Emptied another can of ether, don't seem to have any more vacuum leaks. In fact I can stall the engine by plugging the EACV port with my finger (hicky test) which also stops air flowing to the slow idle adjust screw.
A couple of times now, the engine has suddenly started working. Higher RPM, and engine didn't hunt, error 14, disappeared. Test drove car and no problem. Over night trouble reappeared.
On another occasion trouble went away, mid testing, the MAP sensor was disconnected, the engine was started, then stopped. When car was restarted, (MAP sensor reattached) the engine jumped to about 2000 RPM, twice over 30 seconds, then settled down to work fine, until after increasing the engine load, by turning the head lights on. The engine then went back to it's failed position.
Next thing to test would be the ECU, I give it a 25 % chance of being the fault. Already had the ECU on my workbench, definitely reset the memory.
Dismantled the ECU and traced out the EACV wiring. Nothing fancy, just a simple MOSFET (Transistor) controlled by a signal from the main CPU chip. Applies a ground to the EACV to energize the solenoid.
Question
Does the ECU (obd1) need to learn the "engine" as would an OBD2 ECU
Any suggestions?
quote:
--------------------------------------------------------------------------------
OK here's the status and what I've learned.
What I've learned;
1. With the EACV totally closed and the motor cold, the cold idle valve lets to much air through, the engine hunts for about 1 minute, until the valve starts to close, then it just runs fast (as it should). This is an easy fix, we just cut down on the amount of airflow through that valve, with a brass gasket, restricting the air flow.
2. The ECU outputs a ground signal to the EACV (steady ground, no pulsing) until well after the cold idle valve has closed. This means you have full bypass of the throttle, resulting in much more air than the engine needs. According to the Honda manual, during warm-up the ECU should be opening the valve to allow for faster cold idling. After the ECU shuts the EACV down, the engine drops to slow idle, (450 RPM). There is no further activation of the EACV. The ECU should (per the manual) actually operate the EACV enough to increase warm idle by 300 RPM, it isn't doing this
I monitored this with an oscilloscope, the control was definitely a hard ground with NO pulses. The valve was fully open, max air bypass, until well after the cold idle valve closed.
3. Using my pulse width modulator tester, that I just built, and driving the EACV, I can change the idle to what ever I want, by controlling the air through the EACV, from full open to full closed. This test indicates that the EACV is definitely operating. Also of note is the noise generated by this solenoid valve oscillating on and off, you can definitely hear the operational action.
4. Still getting the EACV fault code 14
5. The Engine still hunts at about 1500 RPM.
6. O2 sensor output;
a; rev engine to 2000RPM, then drop quickly to idle. O2 output goes from .9 volts to about .3 volts, then creeps back up to .9 volts. (O2 test from Honda manual)
b; at idle (approx 750 RPM), O2 output crosses .5 volt level about 7 times in 10 seconds. Engine does not hunt.
c; at approx 2500 RPM, O2 voltage crosses .5 volt level, over 20 times in 10 seconds. Engine does not hunt.
d; at approx 1500 RPM, engine is hunting, O2 output remains at about .3 volts. When RPM is increased, see "c" above.
7. Throttle position sensor varies between .5 volts and 4.5 volts (per service manual)
8. MAP sensor, Ignition ON, car not running, output is 2.9 volts. Engine running at idle, output is .98 volts (varies with engine RPM)
9. Coolant temperature sensor, hot engine, approx 250 ohms.
10. Dist sensors, TDC,Crank,and Cylinder pos. all have signal outputs, measured with an oscilloscope.
11. Vehicle NOT equipped with a ELD (Electric Load Detector), well at least there is no GRN/RED wire on connector D10 of the ECU
12. Timing set per red mark on crank pulley
13. All sensor measurements take at the ECU.
14. Emptied another can of ether, don't seem to have any more vacuum leaks. In fact I can stall the engine by plugging the EACV port with my finger (hicky test) which also stops air flowing to the slow idle adjust screw.
A couple of times now, the engine has suddenly started working. Higher RPM, and engine didn't hunt, error 14, disappeared. Test drove car and no problem. Over night trouble reappeared.
On another occasion trouble went away, mid testing, the MAP sensor was disconnected, the engine was started, then stopped. When car was restarted, (MAP sensor reattached) the engine jumped to about 2000 RPM, twice over 30 seconds, then settled down to work fine, until after increasing the engine load, by turning the head lights on. The engine then went back to it's failed position.
Next thing to test would be the ECU, I give it a 25 % chance of being the fault. Already had the ECU on my workbench, definitely reset the memory.
Dismantled the ECU and traced out the EACV wiring. Nothing fancy, just a simple MOSFET (Transistor) controlled by a signal from the main CPU chip. Applies a ground to the EACV to energize the solenoid.
Question
Does the ECU (obd1) need to learn the "engine" as would an OBD2 ECU
Any suggestions?
it revs from 700-1100 rpm, back and forth like its 'searching' for the correct idel.
