89' Lesabre- "Lean exhaust" trouble...plz read

I just cannot get rid of this problem, I have had the same problem with the car for over a month now. Only occurs when the vehicle has been running for 30+ mins straight, and it runs excellent before that. The car seems as though it is being flooded, and vast amounts of smoke pour out of the tail pipe when i step on the gas. The accelerator hesitates alot, and is nearly impossible to drive with it studdering out. It will not give a diagnostic code until this problem occurs; which I dont understand..but anyway I ran it today and did diagnostics, what came up was "4-4" or "Oxygen Sensor or circuit - lean exhaust detected". When the problem first occured I suspected right away the problem to be the O2 sensor without even doing diag. so I changed it. As the problem continued I had little to no idea what could have been causing it. I will check the connection with the O2 sensor, but am really out of ideas. I have checked the EGR valve, Air Mass, Coolent Temp sensor...Ur thoughts are greatly appreciated, thank you for your time.

Adam

I just cannot get rid of this problem, I have had the same problem with the car for over a month now. Only occurs when the vehicle has been running for 30+ mins straight, and it runs excellent before that. The car seems as though it is being flooded, and vast amounts of smoke pour out of the tail pipe when i step on the gas. The accelerator hesitates alot, and is nearly impossible to drive with it studdering out. It will not give a diagnostic code until this problem occurs; which I dont understand..but anyway I ran it today and did diagnostics, what came up was "4-4" or "Oxygen Sensor or circuit - lean exhaust detected". When the problem first occured I suspected right away the problem to be the O2 sensor without even doing diag. so I changed it. As the problem continued I had little to no idea what could have been causing it. I will check the connection with the O2 sensor, but am really out of ideas. I have checked the EGR valve, Air Mass, Coolent Temp sensor...Ur thoughts are greatly appreciated, thank you for your time.

Adam

Possible causes could be a exhaust leak upstream from the O2 sensor, vacuum leaks, fuel pressure/volume too low (possible causes...fuel filter, fuel pump, fuel regulator), MAF sensor reading lower amount of air flow than actual or partially clogged injectors.

Since you're not getting a code 33 (MAF sensor air flow low), I would assume this device would be working correctly. Therefore, I would focus on vacuum leaks and/or the fuel system. Hope this helps!

A coolant sensor could do thiis. Usually when they fail they fail to -40 degrees and it would run fine cold. Ones it warms up it would flood out.

coolant sensors have nothing to do with the engine being flooded. i would focus on a fuel pressure/pump problem. if not take a look at the coil packs. when they heat up they short out.

coolant sensors have nothing to do with the engine being flooded. i would focus on a fuel pressure/pump problem. if not take a look at the coil packs. when they heat up they short out.
I beg to differ with you. Your ect tells your ecm what temperture the engine is to act like a choke in an old crabed car. The ect richens the mixture up to it does not stumble cold. If stuck at -40 degrees the ecm thinks it is that cold and dumps the fuel to it. GMs are known for this problem. Saturns are even worse. Check out the saturn forums. they go bad all the time. I am not saying that is what his problem is but it could cause it amoung other things and some times does. Thanks