2001 blazer s10 with 4.3 and 151,000 miles, code p0 300 ...changed plugs ,wires, rotor cap , took plenum off noticed fuel in back , replaced fuel regulator , runs and idle's like new. Also cleaned EGR and Idle control valve. Reset computer after 48 miles SES light , checked and got p0171 and p0174 lean both bank 1 and 2 checked @ advanced auto, said 02 sensors and i have 4 . OK , so got under car took off sensors sprayed with carb cleaner to see if it would work , but no dice. Here's the thing I only found 3....
drivers side 1
passenger side 1
and 1 just before the muffler
any idea's ?
BTW, car runs like new and starts on a dime
also a vacuum hose that runs from radiator area to back and into pcv connection was cracked @ connection so I cut and reconnected.
Thanks in advance