Ok , so Ill start this off by stating that I did search, but didn't really find what I was looking for. Basically a couple weeks ago the car was running perfectly fine, no problems what so ever. I had to drive my car from wyoming to ohio (1,400 miles). about 900 miles in i noticed that my car was going really lean at idle 18 + . Under cruise and wot I have no issues at all and my afr's are normal. On cold starts it seems normal as well for the most part. This problem only seems to arise after the car is warm and I come to a stop sign or what have you. It seems to go all the way lean and want to stay there to ten or so seconds then swing back and forth before settling in at normal afrs. Its very inconsistant, but does go lean just about every time I come to a stop. Idle also seems to be very rough from time to time, but my rpms aren't really all that different.

Is this something that I should worry about? Should I stop driving the car? Initially I was thinking plugs, but now I'm not sure. Any advice would be helpful.

Sorry for the jumbled post but I'm typing from my phone. Thanks in advance.

Edit: I forgot to add that at really low rpms while driving the car seems to hesitate and not act normal. Doesnt do this all the time, but is noticable. In boost though it seems completely fine. I'm lost...

 

What wideband are you using? If aem check the sensor. I was having same problem and it turns out my sensor is done. It wouldn move when the sensor was covered with a rag of gasoline it just stayed on full lean, however with the car warmed up and driving it read normal but at idle went full lean.

 

Ya its aem. Ill have to test it later today, but I dont think thats the problem being that my idle itself feels rough as well. Thanks for the input though Ill check that for sure.

 

bump for a little more help

 

it could be the sensor for the WB or it could be o2 sensor. Do you have a CEL?

 

Ya I have a cel, but I had one to begin the drive. It may have thrown another. I will have to go pull it and figure out if I have another.

 

Found some more in depth info for you. Hope it helps a little.

The codes that may give you more problems are PO171-P0175 generic (or similar manufacturer specific) codes. These codes tell you that despite the computers attempts to correct fuel trim (the amount of time the injectors stay on, delivering more or less fuel as needed); it can not obtain the correct air/fuel ratio. These are known as rich and lean codes ... the more oxygen in the exhaust (lean condition) the lower the voltage from the O2 sensor and the more fuel the computer calls for.

The most common issues for lean codes are:

1. Vacuum leaks - check for failed or loose vacuum lines, leaking intake gaskets, intake air tubes loose or any other source of un-metered air leaks (leaks after the Mass Air Flow Sensor)

2. Restricted fuel filter or bent/pinched fuel system lines

3. Incorrect input from other sensors, such as the Mass Air Flow Sensor, which may not always drop a separate code

4. Engine misfire. Yes I know this one may seem weird. You might think that if there is a misfire then you will have all that unburned fuel and it should read rich; right? Well the O2 sensors read only oxygen content in the exhaust, so if you have all that unburned fuel from incomplete combustion then, you guessed it, you also have all that unburned oxygen. High O2 content in exhaust equals a lean reading

 

aem uego's are known for showing lean when the sensor itself is going out i forget the part number but most local parts stores sells them.

had it happen on a friends evo new sensor and everything was fine

 

I think you are more than likely right about this. Check this out...

http://www.youtube.com/watch?v=1mb4VmDd0ao

 

Did you find the problem for this, im getting similar symtoms, thanks

 

9yrs later...

 

Necro bump. It was probably either an exhaust leak somewhere before the wideband O2 sensor or just a failing sensor.