Ok so I am new here sorry if this sounds confusing, I just bought a 2004 S4 Quattro 6spd in Phoenix. I drove it home to Prescott (over a mile high) and the malfunction light came on. Took it to a place to check the code. It said System to lean. I had them clear it. It came on again the next evening. I have never owned an Audi before but I have had a car before that did the same thing but once i cleared it up here it never came back on. We don't have emissions here but should i replace the o2 sensor anyways?? or just give it a couple tanks of gas to maybe go away??

Thanks in advance for any help.

 

If your O2 sensors were going out a scan would indicate that. Your problem is most likely due to the fact that the ECU has not yet learned to compensate for the "thinner" air at your current altitude. I think your first step should be to perform a "throttle body adaptation".

There are a couple different procedures for doing it. Try this one first:

1. Get in your car
2. turn key to on position (do not start)
3. push the gas pedal to the floor and hold it there for a GOOD five seconds
4. turn the key to off and release the gas pedal (DO NOT REMOVE THE KEY FROM THE IGNITION)
5. Wait 2-5 minutes (key in the ignition). you may hear some faint clicks and whirrs from under the hood (very faint)


Another procedure: If you have your radio code, disconnect your battery for about 10 minutes. reconnect. get in the car and turn the key to the "on" postition (no start). wait a minute or two, then start the car.

Or, as you already asked, you can just wait a while and see if it goes away on its own. the ECU should be constantly adapting to changing conditions. it may just take yours a little extra time to get the idea that the air is thin.

finally, a good MAF cleaning may help.

 

Well I tried the first suggestion three times on different days. Should i have it cleared again and see if it comes back on? I havent even ran through one tank of gas yet. I dont think i have the radio code and I dont know what MAF is....but thanks for the ideas.

 

^ Mass Air Flow, its what meters the air thats going into your engine. I also have to suggest following what 02A6Beau has to saying cause they know what they're talking about (not being an *** just hard to find people that know what they're talking about) and if the problem still continues I'd say find a good machanic to look at it. You might save yourself from alot headache that way, I've run into many of them when from the backyard machanics and do-it-yourselfers :P