Q&A

My 3.8L V6 with 75K miles has for the last 4 years had a very intermitant DTC always P0171 usually correcting itself. After several trips to the shop (always at a very rep Cadillac dealer) and they cannot reproduce or find any problem. Now the problem is constant. I have torn the engine down to the heads. replaced intake manifold due to melting caused by the EGR stove pipe. replaced MAP, MAF and both O2 sensors. I have replaced fuel filter. I have had all the injectors cleaned and tested they are all flowing evenly and at the top of spec. range. I have tested for any vacuum leaks. The car runs like new, with no discernably hesitation or other drivability issues. Yet the DTC P0171 still resets, I cam clear the code and drive for a while then the code resets. There does not seem to be any difference how I drive, easy, hard, fast, slow, idle. the code just reappears. Any Ideas would be appreciated.