1999 Mazda 626

Engine Performance problem
1999 Mazda 626 4 cyl Automatic 105000 miles

Engine light is on for sometime, and when the car fully stop in front of red traffic light, feel the idle speed has a sudden drop down then come back up, and the car has vibration during the drop, it happen from time to time if keep stopping. In the extreme case, the car stalled for two times in front of traffic light.

I check the error codes, one is P0455, the other is P1451.

For 0455, definition is " EVAP large leak detected", The EMC has detected a large leak in the EVAP system during a system montor test", and probale causes: 1: defective, loose, or missing fuel cap; 2: EVAP canister broke, hose cracked or not connected; 3: purge or vent solenoid defective; 4: vacuum leak at engine; cause 1 definitely not a concern.

For code 1451, definition is "EVAP system canister vent solenoid circuit malfunction", means that "ECM detected the canister vent solenoid signal moved outside the calibrated parmeters at a specific duty cycle", and probable causes: 1: failed canister vent solenoid; 2: open or shorted circuit condition.

The Car garage want me to change the solenoid first but do not guanrantee solving the problem, is that correct? Wouldn't the frist step is checking the hose or leak? What's your suggestion? In the worst case, how much may be the fixing cost?

Thanks.