2001 yukon 5.3

[husky]

2001 yukon 5.3 is running rough when the engine is cold. My code reader shows 2 codes. Bank 1 is lean and bank 2 is lean. After the engine temp comes up it runs fine. Fuel and air filter are new. Anyone have any ideas? 93000 kms.

[RyanZ71]

I'm wondering if the 02 sensors are bad. The 02 sensors in front of the CAT (closest to the engine) should be heated 02 sensors, those heaters will wear out as will the 02 sensor it self. The ones behind the cat should be ok, the only purpose they serve is to ensure the cat converter is doing it's job. On average the front 02 sensors should be changed out every 100,000 miles, some folks say to just wait till the Check Engine light comes on but with my expierence in the emissions testing field, I saw many 02 sensors which had to be replaced but never set a check engine light.

[Bish]

My o2's went bad at about 80K but the only symptom was drop in gas mileage. I would also think you would get a sensor code instead of lean condition but it is certaily possible they are causing the problem. Granted, when mine failed, I got no code.

 

I would also check the IAC (Idle Air Control). It is part of the throttle body and mine gets filthy dirty in about 40K. You can clean it on vehicle or take it off. I just sprayed the sh!t out of it with Throttle Body cleaner (make sure it is TB safe or it will eat the coating off).

 

Do you run injector cleaner ever? Change fuel filter? Could be plugged injector. Run a couple tankfulls of double dose of Techron and see if that helps. I love Chevron Techron for cleaning fuel delivery.