Car was idling a bit rough (also missed sometimes) after warm-up and it was suggested to me that adjusting the lambda control might eliminate it.

I measured the lambda statically with ignition on and engine off and got the following readings. I used the sears dvm set on %.

30% ignition on, engine not running
80% with throttle opened completely
90% with air flow sensor deflected


After delecting the air flow sensor, the duty cycle changes from 30% to 60% and returns to 30% if I turn the ignition off and then on. Almost like something is being reset.

When I start the car and warm it up, the duty cycle reads at idle in the 38%-43% range (rich) and 41%-49% when I race the engine. The plug on the adjustment screw has been removed so someone has messed with this before. When I push down on the screw with a 3mm allen engine speed changes (runs better), but returns to rough idle when I remove the pressure on the screw.

How do I interpret these readings?

Thanks,

Steve