And yet another posting about the oxygen sensors
Thread Starter
Audiworld Junior Member
Joined: Mar 2005
Posts: 55
Likes: 0
And yet another posting about the oxygen sensors
Hi Audi experts,
My 99' 2.8 A6Q hit the 100K miles and is still running like a champ
I have done the usual stuff (timing belt, cv boots, tune ups, etc) and the car has never failed me...until a couple of weeks ago 
It has been really hot around here and I have had a hard time starting the car a couple times. The starter cranks very well, but the engine just won't fire up until about 10 seconds of cranking. This behavior is erratic as it will start fine 99% of the times.
Last week the check engine light went off once but then it went away the next time I turned the engine on. The last time I took the car to the dealer (2 months ago for the CV boots) he mentioned I was getting an oxygen sensor error. So, it kind of makes sense I start by changing the 02 sensors and see if that fixes the problem.
My question is: does anybody have a link/pics on how to change the oxygen sensors in the A6? I searched in the forum and stoney's links but I couldn't find a DIY kind of guide.
I did read about using a spliced VW sensor here https://forums.audiworld.com/a6/msgs/355780.phtml Any opinions about that? Is it safe to do this?
Thanks a bunch guys!
G
PS: I don't have Vag-com
My 99' 2.8 A6Q hit the 100K miles and is still running like a champ
I have done the usual stuff (timing belt, cv boots, tune ups, etc) and the car has never failed me...until a couple of weeks ago It has been really hot around here and I have had a hard time starting the car a couple times. The starter cranks very well, but the engine just won't fire up until about 10 seconds of cranking. This behavior is erratic as it will start fine 99% of the times.
Last week the check engine light went off once but then it went away the next time I turned the engine on. The last time I took the car to the dealer (2 months ago for the CV boots) he mentioned I was getting an oxygen sensor error. So, it kind of makes sense I start by changing the 02 sensors and see if that fixes the problem.
My question is: does anybody have a link/pics on how to change the oxygen sensors in the A6? I searched in the forum and stoney's links but I couldn't find a DIY kind of guide.
I did read about using a spliced VW sensor here https://forums.audiworld.com/a6/msgs/355780.phtml Any opinions about that? Is it safe to do this?
Thanks a bunch guys!
G
PS: I don't have Vag-com
Tech Guru
Joined: Oct 2002
Posts: 34,430
Likes: 130
Oxygen sensors have nothing to do with cold start.
Sounds more like a problem with the coolant temp sensor to me.
Regardless, I would just randomly replace your O2 sensors. An O2 sensor code can mean any number of things. Even if there is a bad sensor that needs replacement there is little sense in changing all four if the other three are functioning.
I replaced one O2 sensor in my wife's car at 190k
My A4 is still on all four originals at 143k.
Regardless, I would just randomly replace your O2 sensors. An O2 sensor code can mean any number of things. Even if there is a bad sensor that needs replacement there is little sense in changing all four if the other three are functioning.
I replaced one O2 sensor in my wife's car at 190k
My A4 is still on all four originals at 143k.
Thread Starter
Audiworld Junior Member
Joined: Mar 2005
Posts: 55
Likes: 0
Re: Oxygen sensors have nothing to do with cold start.
thanks 4driver4. Well, the problem has also occurred in the nights with cool weather. Would that still had to do with the coolant temp sensor? By the way, the dealer flushed and replaced the coolant 2 months ago.
I thought if the 02 sensor is not working correctly the mix could be too rich and that could lead to flood the car and difficult starts? That is what the dealer told me anyway
Thanks again
G
I thought if the 02 sensor is not working correctly the mix could be too rich and that could lead to flood the car and difficult starts? That is what the dealer told me anyway
Thanks again
G
Tech Guru
Joined: Oct 2002
Posts: 34,430
Likes: 130
The oxygen sensors do not come into play until the system goes into closed loop...
...which is well after starting. If you are having more trouble on cool nights, my guess would be that the coolant temp sensor is not registering that the temp is low and the ECU is not providing extra enrichment for the cool start. The coolant flush should not be a factor.
Thread Starter
Audiworld Junior Member
Joined: Mar 2005
Posts: 55
Likes: 0
Re: Fuel pump failing?
Thanks. How can I know if the pump is failing? I did remove a fuel line in the engine compartment and cranked the car and the gas was coming out with a lot of pressure (I tried to block the flow with my thumb).
This has happen only a couple times, but after it started the car runs as good as usual so I wonder if the fuel pump has much to do with this? Then again, I don't know much about Audi mechanics!
By the way, I replaced the fuel filter about 5K miles ago, and I only use 91 gas from Shell.
Thanks again!
G
This has happen only a couple times, but after it started the car runs as good as usual so I wonder if the fuel pump has much to do with this? Then again, I don't know much about Audi mechanics!
By the way, I replaced the fuel filter about 5K miles ago, and I only use 91 gas from Shell.
Thanks again!
G
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Thread Starter
Audiworld Junior Member
Joined: Mar 2005
Posts: 55
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Re: The oxygen sensors do not come into play until the system goes into closed loop...
Thanks again 4Driver4. That's valuable info.
This hasn't happened more often in cool nights. The problem has happened during cool nights as well as in the middle of the day with 100 degrees!
Speaking about temp, my engine temp gauge (not the oil temp), is usually at the minimum even when I am going up the mountains. I heard that happens to a lot of Audis (the temp gauge, not driving up the mountains ;-) ).
It has been the same way in the last 3 years though. Would that have anything to do with this?
G
This hasn't happened more often in cool nights. The problem has happened during cool nights as well as in the middle of the day with 100 degrees!
Speaking about temp, my engine temp gauge (not the oil temp), is usually at the minimum even when I am going up the mountains. I heard that happens to a lot of Audis (the temp gauge, not driving up the mountains ;-) ).
It has been the same way in the last 3 years though. Would that have anything to do with this?
G
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From: New York Metro
Some observations:
1- VAG COM is your friend - you really need to get the right error codes to see what is what.
2- My gut feeling is there is a problem with your fuel pump/vacuum lines as I recently had the same problem.
3- The fuel filter job that you recently did may be related to this problem as well.
But I would start by VAG COM. Good luck.
2- My gut feeling is there is a problem with your fuel pump/vacuum lines as I recently had the same problem.
3- The fuel filter job that you recently did may be related to this problem as well.
But I would start by VAG COM. Good luck.
Thread Starter
Audiworld Junior Member
Joined: Mar 2005
Posts: 55
Likes: 0
Re: Some observations:
Thanks Nebalt,
I actually changed the filter about a 8 months ago and the problem just started recently. (yeah, it takes me a while to put 5K in that car!)
Was your problem very erratic or constant. Mine is pretty erratic.
Unfortunately I don't have Vag. I will post in my local forum to see if somebody can help me with that. By the way, my check engine light is not on. Would I get any error codes if the light is not on anyway?
Thanks again guys!!
G
I actually changed the filter about a 8 months ago and the problem just started recently. (yeah, it takes me a while to put 5K in that car!)
Was your problem very erratic or constant. Mine is pretty erratic.
Unfortunately I don't have Vag. I will post in my local forum to see if somebody can help me with that. By the way, my check engine light is not on. Would I get any error codes if the light is not on anyway?
Thanks again guys!!
G