Threw a CEL today need some advice
 

Today when I was driving all of a sudden my CEL came on. Went to Autozone and it came up first o2 sensor failure. Anyone else had this problem before? Just to let you guys know I did change to 93 octane like about a month or so ago, would that have anything to do with it?

nah. But - it is an emssions component - wouldn't it be warrantied to 100K miles (by law?)

Excellent point.

And, can you get the p-code for the O2 sensor fault? There is more than one code for emissions related problems that could trip a CEL, and knowing what the code is would help us root cause the issue for you.

I will try to do that

Ok the code that I got was P0171 System too lean (bank 1) what the heck does that mean. I had a CAI for a long time now more then 6 months and 5000 miles. The lastest thing that I did put in was a breather filter could that be whats causing it? Any help would be appreciated.

The O2 sensor is detecting that there is a lot of unburned gasoline in the exhaust. The O2 sensor is supposed to keep your car running at stoichiometric, by adjusting between lean and rich constantly. But your car seems to be stuck on rich... IMO, this is caused by a combustion failure or incomplete combustion. Sometimes the result of ignition system troubles, sometimes the result of there being insufficient air induction. Check the condition of your air filter. Is it dirty, clogged? Check your plugs. Is the gap too big, or do they appear fouled? Check your coils. Are the inputs wires cut or damaged? Does the coil boot or ignition cable make good contact with the plug terminal? Check your MAF. These get dirty. Also, check to make sure the harness to the MAF is in good shape (no cuts or abrasions).

I thought lean was not enough fuel too much air? But Im not sure.

probably a clogged injector on cylinder #1...the filter isnt the problem

Did you mean like an breather (oil) filter? That might be it. To much air maybe!

no thats not it..I have been running a breather filter for about 2 years, plus the crankcase doesnt take in air, it vents air out

IMO, it is going to be something that is somehow measured and evaluated by electronics. Think intake air, ignition, fuel system, etc.

:rolleyes:

p0171 code sounds like a maf problem do see alot of these at dealership, also is engine running smooth ?? . have seen intake gasket leaks which will set same code, alsocheck intake boot after maf for any leaks which will set this code, most of the time it is maf. make sure if you use oil type air filters to use very little oil as some is drawn in maf and can damage it , so give those a try