Need help with O2 sensor
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New Member
Joined: Mar 2008
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Need help with O2 sensor
This is my first time on here, so please forgive if I'm noob at this. I have a 01 A4 1.8T quattro. I have a bit of a problem, and I think that I've isolated it down to it being an O2 sensor issue, basically my CEL came on, and it would lag quite a bit when you're trying to accelerate, so I took it into dealership and get fixed. They replaced injectors on cylinder 3 and 4, the lagging is still there sometimes (very intermittent), but they can't figure out what's going on with it. Today, I tried to go get emission test and I failed with high NOx readings, which points me to O2 sensor. Now I'm wondering how many O2 sensors are on my model and if there's a way to test them before I blindly go and replace them all. Please help!!
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Joined: Feb 2008
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you have two 02 sensors
they are located pre/post catalytic convertor.
If you go to the passenger side of your engine bay and look between the heat sheild and the motor, one will be facing you, further down the exhaust... there is another one. Usually you need to only replace the first one because it is the wideband on our cars. You can order them from avalonmotorsports.com or call 1.303.400.3001... you want the PRE (thanks north) cat 02 sensor.
they are fairly easy to change, just soak the area in pb blaster first. Autozone/canadian tire (depending on location) can loan you an 02 removal set. It makes it alot easier to remove the 02 sensor, however a wrench can work just as well...
the wire is plugged in just behind your coolant tank
hope that helps
If you go to the passenger side of your engine bay and look between the heat sheild and the motor, one will be facing you, further down the exhaust... there is another one. Usually you need to only replace the first one because it is the wideband on our cars. You can order them from avalonmotorsports.com or call 1.303.400.3001... you want the PRE (thanks north) cat 02 sensor.
they are fairly easy to change, just soak the area in pb blaster first. Autozone/canadian tire (depending on location) can loan you an 02 removal set. It makes it alot easier to remove the 02 sensor, however a wrench can work just as well...
the wire is plugged in just behind your coolant tank
hope that helps
Thread Starter
New Member
Joined: Mar 2008
Posts: 6
Likes: 0
Re: Go have the CEL read by a scanner tool and report back. Could be many things.
I believe that they said that it was misfires in cylinders 3 & 4, but now that the injectors have been replaced, it's still the same. Note that also, when the engine is cold, it's more likely to lag. It doesn't help that I'm in Colorado, but yeah, that's the dilemma I'm in. Is there a way to test them out to see if they're in working condition or not?
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