Re: [doc] Erratic

[Martin Gutkowski <webmaster@xxxx>]

Hi Nick - I have a few comments below

Nick Tomlinson wrote:

> Here goes - Unplug the oxygen and sensor but still leave the frequency valve connected. This should give the freq valve a fixed duty cycle.
When you unplug the oxygen sensor, the lambda computer thinks it has 
failed and puts the mixture into "limp home" mode which is over-rich.

> If the engine now idles OK, use an oscilloscope on the oxygen sensor and see if it switches OK (should be a square wave between 200mV and 800mV with frequency of approx 1Hz). 
Even when you've unplugged it? The oxygen sensor works like a tiny 
little battery and provides a voltage according to how much oxygen is in 
the exhaust - the more oxygen there is, the leaner the mixture. If 
you've unplugged the sensor, it'll stay constant at "too rich" - or am I 
missing something here?

> If you have a cat bypass you could leave the oxygen sensor unplugged and set the CO to 1.3-1.5% to run in open loop mode and reconnect the oxygen sensor. The CO should drop to less then 0.3%.
This is waaaaay to lean. The lambda system is designed to function at 
around 1.0%, however without a cat you can partially eradicate the 
effect of the lambda system by tuning the engine to 1.5%, which is how 
the B28E is set up. If you adjust the mixture so that when the lambda 
sensor is plugged in it reads 0.3%, it'll be a tough car to start on a 
cold morning, and you'll lose a lot of power.

Best WIshes

Martin