My 94 Corvette has developed an issue which leaves me scratching my head. When you first start it, before the O2 sensors kick in, everything appears normal. As soon as it goes into closed loop, it begins to add in fuel the longer it runs, until the BLMs max out at 160 after a cell has had enough hits. You can tell it is pig rich by the way it runs and the smell of the exhaust, even though the ECM still thinks it is lean. Now....if I unplug the MAF and put it into speed density mode it does not do this. It runs as normal. The BLMs stay where they should. I have replaced the MAF, as the old one had some corrosion on it, however it has made no difference. . I have searched for vacuum leaks and found none. Suggestions?
Thanks,
Roy