The saga continues... A8 still won't run
02-06-2006, 11:06 PM
#11
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Check that out as mine was sticking open and allowing the fumes to be fed into the manifold
under conditions that it shouldnt.
My tech told me that it only should open under vacum conditions ie strong backing off etc.
There is an output test with vag to check operation but if you clamp off the hose and all runs ok then there is your answer.
Simple test
The evap system is required for emmisions in your country but my tech suggested that I could remove valve and permanently clamp hose thus correcting the issue.
But under warranty I opted to replace.
They treated it as the same claim as the fuel pump as one may have caused the other.Very cool
My tech told me that it only should open under vacum conditions ie strong backing off etc.
There is an output test with vag to check operation but if you clamp off the hose and all runs ok then there is your answer.
Simple test
The evap system is required for emmisions in your country but my tech suggested that I could remove valve and permanently clamp hose thus correcting the issue.
But under warranty I opted to replace.
They treated it as the same claim as the fuel pump as one may have caused the other.Very cool
02-06-2006, 11:12 PM
#13
All right, let's say it doesn't start because rich running fouls the plugs
The throttle position sensor may not have made any difference, just the fresh spark plugs.
Off the top of my head, the things to check would include fuel pressure (maybe a blocked return line to the tank -- it gets removed during pump replacement -- or a bad regulator), coolant temp sensor on the back of the passenger side cylinder head (VAG-COM the engine controller display group 3 field 3; intake air temp is in field 4), and probably not a MAF sensor (but display group 7 field 2 should show 3.9 to 6.5 g/s at warm idle).
The transmission controller, whose 00012 coding you asked about, is not the same box as the engine controller.
A VW dealer would likely have the electronic diagnostic equipment but not the service manuals for your car, and maybe not Audi-specific cartridges for the diagnostic tool (not sure how that works).
Tom
(The TPS may or may not have been bad. Hopefully the shop used something like VAG-COM to read the measuring blocks. I don't particularly trust service manual resistance tests for unplugged potentiometer sensors like the TPS -- they can show extra resistance in the potentiometer wiper contact which the computer can ignore when the sensor is plugged in and operating as a voltage divider. I unnecessarily bought an L-Jetronic airflow meter for my '87 CX because of this phenomenon.)
Off the top of my head, the things to check would include fuel pressure (maybe a blocked return line to the tank -- it gets removed during pump replacement -- or a bad regulator), coolant temp sensor on the back of the passenger side cylinder head (VAG-COM the engine controller display group 3 field 3; intake air temp is in field 4), and probably not a MAF sensor (but display group 7 field 2 should show 3.9 to 6.5 g/s at warm idle).
The transmission controller, whose 00012 coding you asked about, is not the same box as the engine controller.
A VW dealer would likely have the electronic diagnostic equipment but not the service manuals for your car, and maybe not Audi-specific cartridges for the diagnostic tool (not sure how that works).
Tom
(The TPS may or may not have been bad. Hopefully the shop used something like VAG-COM to read the measuring blocks. I don't particularly trust service manual resistance tests for unplugged potentiometer sensors like the TPS -- they can show extra resistance in the potentiometer wiper contact which the computer can ignore when the sensor is plugged in and operating as a voltage divider. I unnecessarily bought an L-Jetronic airflow meter for my '87 CX because of this phenomenon.)
02-06-2006, 11:16 PM
#14
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not unless it is really extreme
I had no purge valve codes even but that was the problem.
I found that group 11 in vag was running at -25 [really rich ] when car was running like a dog and when not 02 was all good
the difference was the valve stuck open.
it is supposed to open and shut rapidly and only when needed
I found that group 11 in vag was running at -25 [really rich ] when car was running like a dog and when not 02 was all good
the difference was the valve stuck open.
it is supposed to open and shut rapidly and only when needed
02-07-2006, 12:32 AM
#17
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its under this cover.
<center><img src="http://pictureposter.audiworld.com/96745/engine_pic_evap_valve.jpg"></center><p>clamp the engine side pipline and run car.
If it runs ok then that is the problem
If it runs ok then that is the problem
02-07-2006, 04:20 AM
#19
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Shouldn't be that hard to get running
It's either fuel or spark that is missing, plus you need compression. Let's assume you have compression.
As Tom mentioned, crack the high pressure fuel line after trying to start it and see if it leaks fuel all over, if so, you have fuel pressure. If not sure, test the fuel pressure and flow rate per the Bently.
VAG-COM it and it will tell you if the cam position sensor is working or not.
Another thing to do is to unplug the MAF, and the ECU will go into a default programing looking at engine RPM and throttle position and guess A/F mixture, it might run better then.
If your mechanic does not have the Bently, VAG-COM and experience with Audi's, bring it to somebody who does.
And I do have a spare ECU if you need it to test.
As Tom mentioned, crack the high pressure fuel line after trying to start it and see if it leaks fuel all over, if so, you have fuel pressure. If not sure, test the fuel pressure and flow rate per the Bently.
VAG-COM it and it will tell you if the cam position sensor is working or not.
Another thing to do is to unplug the MAF, and the ECU will go into a default programing looking at engine RPM and throttle position and guess A/F mixture, it might run better then.
If your mechanic does not have the Bently, VAG-COM and experience with Audi's, bring it to somebody who does.
And I do have a spare ECU if you need it to test.
