An idea for the irregular idle:
As the coolant reaches about 40*C the thermal contact will close at the front of the RH intake port.
As soon as the thermal contact closes the bimetallic throttle bypass valve (mounted to the RH intake
port too, under the intake manifold) will close in order to lower the idle RPM, and the ECU will start using
the lamda sensor's signal for the mixture formation. Considering the leak in the exhaust the lambda sensor
may sends inaccurate signal to the ECU, especially when the sensor is old. Try to disconnect the signal
wire of the sensor to see it makes any difference (on some model variations the lambda sensor is omitted.)
If the idle RPM is still low/irregular at operating temperature (with lambda sensor disconnected) there might
be a leak in the intake system, which could explain the screaming hamster. (as the throttle bypass valve
closes the depression between the the valve outlet and the intake will raise significantly that alters the suction
noise too)
As the coolant reaches about 40*C the thermal contact will close at the front of the RH intake port.
As soon as the thermal contact closes the bimetallic throttle bypass valve (mounted to the RH intake
port too, under the intake manifold) will close in order to lower the idle RPM, and the ECU will start using
the lamda sensor's signal for the mixture formation. Considering the leak in the exhaust the lambda sensor
may sends inaccurate signal to the ECU, especially when the sensor is old. Try to disconnect the signal
wire of the sensor to see it makes any difference (on some model variations the lambda sensor is omitted.)
If the idle RPM is still low/irregular at operating temperature (with lambda sensor disconnected) there might
be a leak in the intake system, which could explain the screaming hamster. (as the throttle bypass valve
closes the depression between the the valve outlet and the intake will raise significantly that alters the suction
noise too)
