Hi lamont58,
The idling speed dropping could be due to a fault with the idling system.
DTC P1456 & P1457: EVAP SYSTEM LEAK DETECTED
NOTE:
DTC P1456 indicates Evaporative Emission (EVAP) control system leak detected in fuel tank system. DTC P1457 indicates EVAP control system leak detected in canister system.
NOTE:
Components and/or systems listed in the following steps do not apply to all vehicles, refer to vehicle underhood EMISSION GROUP IDENTIFICATION label for confirmation.
1. If either DTC P1456 or DTC P1457 sets check for:
"Â A faulty fuel filler cap.
"Â Proper vacuum connections.
"Â Fuel tank leak.
"Â EVAP control canister vent shut valve malfunction.
"Â EVAP control canister vent shut valve circuit malfunction.
"Â EVAP purge control solenoid valve malfunction.
"Â EVAP purge control solenoid valve circuit malfunction.
"Â EVAP by-pass solenoid valve malfunction.
"Â EVAP by-pass solenoid valve circuit malfunction.
"Â Fuel tank pressure sensor malfunction.
"Â Fuel tank pressure sensor circuit malfunction.
"Â EVAP control canister malfunction.
When was the last time the engine was tuned?
When the CEL is showing, the PCM could work in backup mode for some sensors and that can cause increase in fuel consumption.
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Sunday, May 16th, 2010 AT 8:43 AM