Would a failing maf cause motor to run rich? Or just poorly? I did the timing belt on my kids 3.0 vue and started motor with maf unplugged. Got a smoke screen initially. Plugged it in and it runs fine. Looking at 2nd indenticL vue but owner says it smokes slightly and seems to have a rich/gassy exhaust. I think the fpr is odd on this motor. It’s not the Honda motor. It’s the 3.0 opal motor.
When it detects the maf isn’t working, the engine computer probably estimates the intake air flow based on the throttle position sensor, and other sensor readings. So as not to leave the owner stranded. Once the O2 sensor warms it, then it will add that to the mix to adjust the fuel injection rate. But it won’t be as accurate as if the maf was working correctly, so it could cause a rich or lean condition, especially during engine load changes.
An engine can have all the sensors functioning but still run rich, for example if the injectors weren’t balanced properly. Or unmetered air was entering the engine or exhaust system.
+1 to George’s post.
"Or unmetered air was entering the engine or exhaust system"
by this comment I believe George is referring to an air leak in the induction system after the MAF sensor or in the exhaust system before the upstream oxygen sensor.
When considering an aging vehicle you must see the vehicle in person. What the seller claims is a bit of smoke is probably oil burning smoke, rich burning smoke is less likely.
Owner added that the exhaust flange is broke so engine is loud. Hmm, need to look at y-pipe setup on this v-6. Sometimes they are complicated. He lowered price to $475