p0466
#2
11-27-2011 | 08:55 AM
April 2011 ROTM
Joined: Mar 2009
Posts: 21,770
From: Tokeland, Washington
ROTM Winner's Club
a good first move is a new gas cap. check along the underside for damage to any wiring or hoses. there is some info on evap system in the how to and faq sticky at the top of the 4th gen seciton
Last edited by craby; 11-27-2011 at 08:59 AM.
#3
11-27-2011 | 09:00 AM
April 2011 ROTM
Joined: Mar 2009
Posts: 21,770
From: Tokeland, Washington
ROTM Winner's Club
found this too
You either have a vacume leak or it could be the evaporative purge flow sensor. The PFS is a three-wire thermistor, with a battery voltage feed, a ground wire, and a signal wire going to the powertrain control module (PCM). The wire going to the PCM has 5 volts on it with the sensor disconnected, which is sent out by the PCM. The sensor then varies the resistance to ground based on the amount of flow through the sensor. As the airflow increases, the resistance increases proportionally, and the voltage increases as a result. The PFS is located between the engine and the canister purge solenoid. Depending on the vehicle, there will be either ported or manifold vacuum to the system.
When the PCM decides to test the system, it energizes the canister purge solenoid, and then monitors the voltage change on the PFS. A typical system starts out with the PFS voltage being somewhere between 0.7v and 1.7v. Once the canister purge solenoid has been energized and there is good airflow through the system, voltage should increase by approximately 1.5v.
The key is to make sure the airflow is good. One way to do this is to remove the hose from the charcoal canister so that it's open to atmosphere, and then manually ground the canister purge solenoid. The hose should then have good, strong vacuum from the engine. Obviously, if it's a ported vacuum system, it will be necessary to rev up the engine to create a vacuum on the system. If airflow through the system is good, and the voltage on the purge flow sensor does not change accordingly, verify that the power and ground feeds are OK. Then make sure there is 5v on the signal wire with the sensor disconnected to verify that the wire is not shorted to ground. If everything checks out OK, but the sensor voltage does not increase properly with increasing airflow, then you have a bad purge flow sensor. If the airflow is not good, check for a bad canister purge solenoid or blocked/collapsed hose.
You either have a vacume leak or it could be the evaporative purge flow sensor. The PFS is a three-wire thermistor, with a battery voltage feed, a ground wire, and a signal wire going to the powertrain control module (PCM). The wire going to the PCM has 5 volts on it with the sensor disconnected, which is sent out by the PCM. The sensor then varies the resistance to ground based on the amount of flow through the sensor. As the airflow increases, the resistance increases proportionally, and the voltage increases as a result. The PFS is located between the engine and the canister purge solenoid. Depending on the vehicle, there will be either ported or manifold vacuum to the system.
When the PCM decides to test the system, it energizes the canister purge solenoid, and then monitors the voltage change on the PFS. A typical system starts out with the PFS voltage being somewhere between 0.7v and 1.7v. Once the canister purge solenoid has been energized and there is good airflow through the system, voltage should increase by approximately 1.5v.
The key is to make sure the airflow is good. One way to do this is to remove the hose from the charcoal canister so that it's open to atmosphere, and then manually ground the canister purge solenoid. The hose should then have good, strong vacuum from the engine. Obviously, if it's a ported vacuum system, it will be necessary to rev up the engine to create a vacuum on the system. If airflow through the system is good, and the voltage on the purge flow sensor does not change accordingly, verify that the power and ground feeds are OK. Then make sure there is 5v on the signal wire with the sensor disconnected to verify that the wire is not shorted to ground. If everything checks out OK, but the sensor voltage does not increase properly with increasing airflow, then you have a bad purge flow sensor. If the airflow is not good, check for a bad canister purge solenoid or blocked/collapsed hose.
