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Re: URQ sorting out....LONG REPLY

Excerpt from the Intro to Maint and Adjustments QUATTRO:

If duty cycle cannot be adjusted or if duty cycle does NOT Fluctuate
check the operation of the oxygen sensor. 

1. Check open loop signal:
trip full throttle switch (engine at idle so idle switch is closed).
Duty cycle reading 50% +/- 6%.

	No duty cycle reading   check test plug connections
	No duty cycle reading   check F/TCU electrical circuit
	Duty cycle incorrect	check F/tcu electrical circuit

2. Check full throttle enrichment:
Remove wire from idle switch,trip full throttle switch. 
Duty cycle should go to 70/77%,CO % should increase.

	a.Duty cycle incorrect    check F/TCU electrical circuit
	b.CO does not increase    check power to freq valve
	   but duty cycle ok

3. Cranking enrichment
Disconnect o2 sensor and coolant temp sensor,ground coil wire
Crank engine duty cycle reads 80%

	a.Duty cycle incorrect	  check F/TCU electrical circuit

4. Cold running enrichment
Start engine disconnect o2 sensor,disconnect coolant temp
sensor.Duty cycle goes to 95% for up to 30sec. then reads

	a.Duty cycle incorrect    check F/tcu electrical circuit

5. Open loop
Disconnect o2 sensor,disconnect and plug crankcase vent hose.
Disconnect evap emissions hose and plug intake air duct
adjust CO to 0.8 +/- 0.4%

	a.CO cannot be adjusted	   repair fuel system 
                      HC not ok    or engine defect.

	If the CO is OK with the o2 sensor disconnected
	yet duty cycle with sensor connected is incorrect

The o2 sensor output goes to the ECU which in turn tells the 
Freq Valve what to do. Any open,shorted,high resistance wires
or connections will create a problem obviously.

Pin 8 on ECU connector to freq valve (it also goes to 
	two pin test plug)
Pin 6 on ECU connector to center on o2 connector
    5 on ECU goes to o2 sensor shield
Pin 10   ECU goes to coolant temp sensor
Pin 15   ECU goes to Idle switch
Pin 21   ECU goes to Full throttle switch

There is a bit of a strain on the ECU connector wires so
it's not unusual to find a broken wire under the cover 
of the plug.

If everything checks out in tests 1 thru 4 then the 
Ecu needs to be checked out or swapped for a known
good one.

If there are any blatant errors in the above someone
will corect any errors I have made. I hope!!!