Haltech Wideband 02 Controller Manual - Manual (Page 13)

8. Tips, Tricks and Troubleshooting
8.1 General measurement requirements
The HWC measures the air-fuel-ratio by measuring the amount of oxygen in the exhaust (for lean
conditions) or the amount of unburned or partially burned fuel (for rich conditions). You should
correct for the following in order to get optimum results from the HWC
1) An exhaust leak will allow oxygen to enter the exhaust stream and therefore will
measure leaner than the engine is actually running. For correct measurement, air-
leaks in the exhaust MUST be prevented under all circumstances.
2) Missing ignitions (where the air-fuel mixture does not ignite) also pump unburned
oxygen into the exhaust and cause the HWC to measure lean.
3) The only circumstance where the HWC will measure richer than the engine is
running is if the pressure in the exhaust tract is excessive (and the engine is running
on the rich side to begin with).
8.2 Vehicles with ‘smog-pumps’
Older fuel injected vehicles with a ‘smog-pump’ actually inject air into the exhaust stream to aid
their catalytic converter in the burn-up of unburned or partially burned fuels. This additional air will
make the exhaust look leaner than the engine is running. For an accurate measure, install the
HWC sensor up-stream of the outputs of the smog-pump. If this is not possible, temporarily
disable the smog-pump by removing its drive belt.
8.3 Measuring at the tail-pipe
On non-catalytic converter equipped vehicles it is possible to measure the air-fuel-ratio at the tail-
pipe. Without it too much outside air may enter the exhaust, especially at idle, to prevent correct
measurements and leading to a lean measurement. Sticking the sensor itself into the exhaust
pipe can yield inconsistent results because the sensor will not have outside air available as a
reference gas and its reaction time becomes so slow that the HWC will report a sensor timing
error. The oxygen sensor needs to have the back part of the sensor (where the wires enter the
sensor) exposed to outside air.
8.4 Single Cylinder Engines
These kinds of engines are difficult to measure at the tail-pipe. The oscillations of the exhaust
gas are so large that a lot of outside air enters the exhaust and prevents correct measurement.
Sometimes it helps to just wrap a piece of heat resistant cloth around the exhaust clamp to
prevent outside air from entering the exhaust.
8.5 Diesel Engines
Diesel Engines and gas turbines run at wide open throttle at all times. They do not have a throttle
but regulate power by the amount of injected fuel. The HWC can still be used, but measurements
at idle will read as lean.
8.6 Reference cell or Pump cell circuit open or shorted errors
Under some rare circumstances it is possible that the heater calibration data in the HWC can
become partially destroyed. This can manifest in the above-mentioned errors. Follow the steps in
chapter 4 ‘First time use’ to reset the heater calibration data.
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