Replaced my MAF Sensor a couple of days ago and all was well. Today the CEL came on so I pulled a code P2098 for the downstream O2 too lean. Maybe not the smartest thing to do but I have been using 89 octane ($4.69 gal) with no problems. I don't remember if it had ethenol in it or not. So my plan is to run the fuel down to 1/4 tank and fill with 93 octane premium fuel ($5.15 gal) and see what happens. Guess it could be other things as well like an exhaust leak or a bad O2 Sensor.

Update: I do have to say that the CEL has always gone on and off the whole 2-1/2 years I've owned the car but didn't own a code scanner till very recently. I also, until last month or two, have been using 91 octane gas.

As I sit here typing I just heard on the local news, Tampa FL, that if people filled up this past weekend we may have contaminated gas. Which i filled up all my vehicles!!!

 

If the fuel is contaminated, and certainly with water (which can mean extra O2 in the exhaust), all you can do is wait for a new fuel fill. REMEMBER: at the extreme temperatures in the combustion chamber, elements can separate and combine that won't do so at room temperature and pressure. In fact, that is the reason we have EGR systems and cats. Read about why you have an EGR system and you will get the idea. SO I'd relax and burn off that gas and see how things go next time.

Running 89 octane is like running 20W50 conventional motor oil or paper oil filters, do whatever you want to, it's your car.

 

They say the contaminant is diesel.

 

I didn't know that! Thanks

 

Update: I do have to say that the CEL has always gone on and off the whole 2-1/2 years I've owned the car but didn't own a code scanner till very recently. I also, until last month or two, have been using 91 octane gas.

 

I do not believe using mid grade fuel in your XF would hurt your motor.


.

 

CEL light has been off today. Don't know why because I've not done anything. Just waiting for the next time it comes on. I'll pull codes in the morning to see if anything else shows even though CEL is off.

 

The CEL is still off and this is 14 Sept. "Could" CEL be associated with me not driving at hi-way speeds very often? I am just putting around town at usually about 35 mph. Might try and get risky and find a place to drive her up to 50mph. LoL