Intermittent engine (motor) symbol on dash

[cedarwoodron]

I have a 2007 Mercury Mountaineer 6 cyl AWD Premium SUV.

I have been getting a periodic engine light on my dash. It come3s on for a day or two (steady light, not flashing), then goes away for a few days, then returns/
I went to AutoZone and they ran a computer diagnostic, which came up with four possibilities:
- fuel pressure low, meaning the fuel pump is defective
- fuel pressure regulator defective
- replace fuel filter
- replace fuel rail pressure sensor

I have had no fuel flow issues- hesitations, non-starts, or any other indicators of poor fuel line flow to the engine.

What is the most likely cause of this on again/off again engine light?

Cedarwoodron

 

[Bobmbx]

Start with changing the fuel filter. It probably needs to be replaced anyway. The fuel pressure low code is telling you that your fuel pressure is below specs, but not necessarily below the point of poor performance. The intermittent nature is another clue. It sounds like you're bouncing back and forth between satisfactory and unsatisfactory pressure.

Just curious, what code numbers did they find?

 

[Flag Gibby]

On these vehicles Ford calls for a new fuel filter every 30k miles so if it has not been done then that should take care of the issue. If you hook up a good code reader to the vehicle you should be able to see what the fuel pressure is at. I actually went only 45k miles on a fuel filter once (and towed a moderately heavy load 400 miles just before I was forced to change it due to the engine running rough) and ended up burning up two of the spark plugs from the cylinders running too lean and got no fuel pressure DTC.