# O2 Sensor Failure Symptoms?



## blankster83 (Jul 25, 2004)

I'm not too good in explaining what it is exactly that my car is doing but I'm expecting that it's the O2 sensor going out. In a nut shell, the engine just doesn't seem to rev up as smoothly when I accelerate. When I start up the engine cold, that when I can notice it the most. If I pump the throttle, the engine doesn't respond like it used to. I'm not sure if this could be an early indication that my MAF is going out or what.. I've got a P-flow intake on it so I imagine that affects the lifespan of the MAF sensor. Anyway, what are the symptoms that you will notice when your O2 sensor is going out? There are no codes being thrown right now and the CEL has never gone on... but it's getting worse to the point to where I want just want it to get fixed. Plus, I'm only 1k away from 50k so I want to make sure that any fixes are covered under warranty. Any help will be appreciated!


----------



## PhReE (Sep 16, 2004)

*Re: O2 Sensor Failure Symptoms? (blankster83)*

So, why do you think its the O2 sensor, and then when you started thinking about it you suggested the MAF but went back to O2 sensor? If the O2 was bad I would bet there'd be a CEL. Sounds like you just need to clean your MAF and change your plugs. Have you changed the plugs yet?


----------



## blankster83 (Jul 25, 2004)

*Re: O2 Sensor Failure Symptoms? (PhReE)*

i've actually already cleaned the MAF and changed the spark plugs. The only thing that makes me think that it's the O2 sensor is because it is far worse when the engine is cold. I'm not a mechanic so I could be totally off... but I've read other posts that lead me to believe that this was a possibility. Any more ideas?


----------



## ELPAISAC (Dec 4, 2003)

*Re: O2 Sensor Failure Symptoms? (blankster83)*

Make sure the coils are properly connected and the gap on the plugs is se right. I've heard of that happening.


----------



## MD-82 (Aug 22, 2002)

This is exactly the same problem I have. Been doing it for more than a year now. I fear the O2 sensors too because I've done just about everything else. Water temp sensor, new MAF, new coils TP readjustment. Still does it. Plus I don't think the ECU is going throw a code that quick. I think a limit needs to be exceeded. Thing is that an O2 is expensive and I have 4 of them under my VR6 so it's twice the cost. If you happen to change yours let us know if it fixed your problem.
Xander


----------



## magman (Jun 22, 2001)

*Re: (MD-82)*

You guys need to find a friend with a vag-com setup then do some live data collecting of the O2 output voltages.
You will soon see if they are on the way out.
IIRC any fault with the O2 sensor will throw a cel.


----------



## PhReE (Sep 16, 2004)

*Re: (magman)*

I have vag com, what kind of ranges should they be? What is the number of the channel to monitor for o2? I can monitor mine and get some base logs I guess, my car seems to run fine. (32k Mi)


----------



## Banditt007 (Oct 23, 2002)

*Re: (PhReE)*

correct me if i'm wrong here (i am basing this off of how digi 2 works) but the 02 sensor needs to get heated up before it works right, even the ones that 'self heat' and do not rely on exhaust gas temperature to get up to operating temp, still take alittle while to work.
The o2 sensor should not even be in the picture before the car is fully warmed up (i'm guessing 5 minutes after she registers 190 on the not-accurate-at-all-and-misleading-temperature gauge)
vagcom would prob tell u fo' sizzle.


----------



## PhReE (Sep 16, 2004)

*Re: (Banditt007)*

Well does vag com at least have a readout on one of the channels for the o2 sensor reading? Or no? I would guess yes but not sure.
But yeah I would guess the ecu wouldnt use the o2 sensor in warmup mode, ... isnt that right? I seem to remember warmup mode is based just off maps pretty much.


----------



## Banditt007 (Oct 23, 2002)

*Re: (PhReE)*

from what i know about my digi 2, and most if not all cars for that matter is the very intital start up is based off of maps in the ECU after a few seconds it uses the maps in the ECU and the coolant temp sensor....then once fully warmed up the coolant temp sensor and the 02 sensor, as long as you arent in WOT


----------



## TexasCorrado (Apr 24, 2005)

*Re: (Banditt007)*

Check all your grounds. Make sure they are good to go. Whenever you find the problem, please post what is was. Thanks


----------

