Hello guys,

I have a strange problem with the V6 3.1 engine in my Firebird. We have replaced two injectors 'cause the resistance was bad, should be somewhere between 11-12 Ohm.
One was 7 and the other round about 10 Ohm.

The car runs so far, but when its warm enough the idle run turns to crap. We have logged the O2 sensor data to see what happens there (attachment).

My question is, shouldn't the o2 sensor run up and down on the graphic continously? On idle it seems to be lean all the time, then when I hit the gas pedal its rich.

99.000 mls on the car. I don't know if the o2 sensor has been replaced in the past.

Could this also be caused by a faulty injector? Or is it definitely the o2 sensor? vacuum lines look good. The car has no catalytic converter, could this also raise problems?

Ignition timing is set (with EST wire disconnected) to 10° before. When EST is connected I can see using the timing light that the ignition timing changes to round about 20° before. Is this normal?
ICM has been replaced. New distributor cap and rotor. New spark plugs. New spark plug wires. two injectors are new too.

thanks.