hey guys...So my moms winter beater needs some love. I need to get it through emissions (they just read codes in CT now)..anyways, I have po172, po175 that came back. Now it has a fresh tune up (did it beginning of December, also has new O2 (all 4). new IAC (start/stall issue)...I was a Ford tech, but right now, all my diag tools are not near where I am. I'm kinda thinking MAF, or fuel pressure...anyone have similar issues?It runs great with the tune up, etc...just won't pass with the light on.
oh, and its a 99 exploder, eddie bauer edition with a 5.0
could be MAF sensor needs cleaned, or could be vacuum leak causing the "rich fuel" code. i would look for vacuum leaks on small hoses and PVC valve first- thats the easy thing. pull each hose off the tubes and see if any are cracked, hard, or loose on the tubes.
Lets think about this. "Bank 1 & 2 RICH".... How is a vacuum leak going to set this code. Rich= too much fuel. The system is seeing more fuel in the exhaust then it wants. So in other words your fuel trims are below -10 or so. You need to be looking at either high fuel pressure, intake restriction(i.e..air filter plugged), or possible incomplete combustion. Could be a stuck open injector, but if your not having any misfire problems or codes, chances are thats not your issue. You might also want to see what your MAF is reading. PCM might think it's getting more air then it actually is and lengthening your injector pulses causing a rich fuel mixture. Vacuum leaks are going to cause LEAN codes because of the extra unmetered air being sucked into the cylinders.
I can't remember the years, but some of the explorers also had issues with hanging injectors during cold starts. They would free themselves as the engine warmed up. But being both banks are rich, chances are this is not your issue.