Questioning the reliability of the 996 (starting problems) + Fuel Vent System(PICS)
07-20-2010, 04:58 PM
#151
Rennlist Member
07-20-2010, 06:25 PM
#152
07-20-2010, 06:55 PM
#154
Rennlist Member
Cool....that valve if clogged or partially clogged will give an insufficient pressure reading and wont open/close properly when it supposed to. If that doesnt work, try the MAF. I understand people are strapped for "play" money, so lets start with the cheapest part first and work our way to the MAF.
07-20-2010, 07:18 PM
#155
Cool....that valve if clogged or partially clogged will give an insufficient pressure reading and wont open/close properly when it supposed to. If that doesnt work, try the MAF. I understand people are strapped for "play" money, so lets start with the cheapest part first and work our way to the MAF.
07-20-2010, 11:12 PM
#158
07-21-2010, 12:20 AM
#159
Some basics of the system ....
2000 Porsche 911 Carrera Cabriolet (996) F6-3.4L
Vehicle Level Powertrain Management Emission Control Systems Evaporative Emissions System Testing and Inspection Evaporative System Monitoring
Evaporative System Monitoring
Evaporative System Monitoring
General Description
The fuel evaporative system monitoring permits detection of leaks with a diameter of 1-mm or larger in the fuel evaporative emission control system. Additionally, the monitoring system can detect a malfunction of the fuel tank pressure sensor (DST), canister close valve (AAV), or purge control valve (TEV).
The system monitoring is performed by observing the fuel tank. A canister close valve (AAV) and a purge control valve (TEV) are used to open and close the system.
Monitoring Conditions
The leak test will be conducted when the vehicle is at an idle condition with zero vehicle speed.
Plausibility Check DST
The TEV is closed by a continuous reduction of its duty cycle. Afterwards the pressure is observed. If the pressure falls short of a threshold (vacuum) for a given period, an AAV malfunction is detected (AAV blocked) and monitoring is stopped. If the pressure is not steady, a DST malfunction is detected and monitoring is stopped.
Measuring of Compensation Gradient
If the pressure is steady and the AAV closed, the pressure increase caused by fuel evaporation is measured and stored after a certain period. If the pressure reaches a specific threshold, monitoring is stopped, because the fuel evaporation is excessive. If the pressure reaches a specific threshold (vacuum), a TEV malfunction is detected (TEV stuck open) and monitoring is stopped.
AAV-Check
The AAV is opened and TEV are opened by a constant increase in their duty cycle. If the pressure reaches a specific threshold (vacuum), an AAV malfunction is detected (AAV blocked) and monitoring is stopped. If the pressure does not reach this specific threshold and the TEV has reached a certain duty cycle, the AAV is closed after a time delay.
Large Leak Detection
If a large lean correction of the lambda controller is detected, monitoring is stopped. If monitoring were to be continued, idle instability will occur because of the high canister load. If the negative pressure build-up gradient is below a certain threshold, a large leak is detected and the diagnosis is complete. If the pressure reaches a certain threshold (ex. -8 hPa), the TEV is closed. If the pressure reaches a specific threshold (ex. -15hPa), a TEV malfunction is detected (TEV stuck open) and monitoring is stopped.
Small Leak Detection -1.0mm
The system is now considered sealed. The gradient of the negative pressure decay is converted into a volume flow (air streaming in through a leak). Afterwards a volume flow balance is realized. The leak volume flow is derived from the volume flow balance. If the leak volume flow reaches a certain threshold, a small leak is detected and the diagnosis is complete.
Very Small Leak Detection (0.8mm)
When the Small Leak Detection is finished the same procedure is repeated in a following idle period but with a different level of vacuum and a different (more stringent) threshold. A leak of app. 0.8mm can be detected.
2000 Porsche 911 Carrera Cabriolet (996) F6-3.4L
Vehicle Level Powertrain Management Emission Control Systems Evaporative Emissions System Testing and Inspection Evaporative System Monitoring
Evaporative System Monitoring
Evaporative System Monitoring
General Description
The fuel evaporative system monitoring permits detection of leaks with a diameter of 1-mm or larger in the fuel evaporative emission control system. Additionally, the monitoring system can detect a malfunction of the fuel tank pressure sensor (DST), canister close valve (AAV), or purge control valve (TEV).
The system monitoring is performed by observing the fuel tank. A canister close valve (AAV) and a purge control valve (TEV) are used to open and close the system.
Monitoring Conditions
The leak test will be conducted when the vehicle is at an idle condition with zero vehicle speed.
Plausibility Check DST
The TEV is closed by a continuous reduction of its duty cycle. Afterwards the pressure is observed. If the pressure falls short of a threshold (vacuum) for a given period, an AAV malfunction is detected (AAV blocked) and monitoring is stopped. If the pressure is not steady, a DST malfunction is detected and monitoring is stopped.
Measuring of Compensation Gradient
If the pressure is steady and the AAV closed, the pressure increase caused by fuel evaporation is measured and stored after a certain period. If the pressure reaches a specific threshold, monitoring is stopped, because the fuel evaporation is excessive. If the pressure reaches a specific threshold (vacuum), a TEV malfunction is detected (TEV stuck open) and monitoring is stopped.
AAV-Check
The AAV is opened and TEV are opened by a constant increase in their duty cycle. If the pressure reaches a specific threshold (vacuum), an AAV malfunction is detected (AAV blocked) and monitoring is stopped. If the pressure does not reach this specific threshold and the TEV has reached a certain duty cycle, the AAV is closed after a time delay.
Large Leak Detection
If a large lean correction of the lambda controller is detected, monitoring is stopped. If monitoring were to be continued, idle instability will occur because of the high canister load. If the negative pressure build-up gradient is below a certain threshold, a large leak is detected and the diagnosis is complete. If the pressure reaches a certain threshold (ex. -8 hPa), the TEV is closed. If the pressure reaches a specific threshold (ex. -15hPa), a TEV malfunction is detected (TEV stuck open) and monitoring is stopped.
Small Leak Detection -1.0mm
The system is now considered sealed. The gradient of the negative pressure decay is converted into a volume flow (air streaming in through a leak). Afterwards a volume flow balance is realized. The leak volume flow is derived from the volume flow balance. If the leak volume flow reaches a certain threshold, a small leak is detected and the diagnosis is complete.
Very Small Leak Detection (0.8mm)
When the Small Leak Detection is finished the same procedure is repeated in a following idle period but with a different level of vacuum and a different (more stringent) threshold. A leak of app. 0.8mm can be detected.
07-21-2010, 12:34 AM
#163
Thats not the voltages,sorry but I don't have a 2000 996 in the shop at the moment to measure, but it should be enough for you to confirm if it's bad or not.
Although with the noise you are having and the problem, it's a pretty good guess. As said by others it's fairly common to see it go bad, and the usual complaint is of the noise.
Although with the noise you are having and the problem, it's a pretty good guess. As said by others it's fairly common to see it go bad, and the usual complaint is of the noise.
07-21-2010, 11:23 AM
#164
Thats not the voltages,sorry but I don't have a 2000 996 in the shop at the moment to measure, but it should be enough for you to confirm if it's bad or not.
Although with the noise you are having and the problem, it's a pretty good guess. As said by others it's fairly common to see it go bad, and the usual complaint is of the noise.
Although with the noise you are having and the problem, it's a pretty good guess. As said by others it's fairly common to see it go bad, and the usual complaint is of the noise.
It seems to me that the TEV is also known as the regeneration valve.
