Federal 2WD Models
On 1.8L engine, fresh air is supplied to the exhaust ports of both cylinder heads through 2 ASV-I with cut-off valves. Both ASV-I units on No. 1/No. 3 and No. 2/No. 4 cylinders operate simultaneously. See Fig 1 .
On 1.6L engine, fresh air is supplied to the exhaust ports of No. 2/No. 4 cylinder sides by 1 ASV-I. An air suction valve (ASV-II) without cut-off valve is installed on the exhaust pipe and supplies fresh air to the exhaust port near the up stream portion of the oxidation catalyst.
The ASV-II without cut-off valve always operates, regardless of coolant temperature and electronic control module signal.
The ASV-I with cut-off valve is controlled by coolant temperature sensed by the thermosensor and time governed by the ECM. When coolant temperature is less than 95° (35°C), the ECM signals the solenoid valve to allow manifold vacuum to open the cut-off valve. This enables the air suction valve to operate.
The solenoid valve I remains open for a period of 123 seconds. During this time, if low vacuum condition should exist, check valve II is used to maintain vacuum at the solenoid and cut-off valves.
At the end of the 123 second period, the control module turns off the solenoid valve II signal. Vacuum is no longer supplied to the cut-off valve and air injection is terminated.