I have a 1994 xjs witg a 4L engine that is showing a code ff26. Could this be because of an exhaust leak from the engine area? I smell fuel vapor through the passenger side window opening as I drive the car.

 

Fr. Rick,

It could be an oxygen sensor fault, however as with all XJS faults, I would suggest that you start by clearing the fault code and see if it returns.

Good luck

Paul

 

I have done that and the code reappears, sometimes after a day or two.

 

Fr. Rick,

As you probably know, an FF26 is a fault code that indicates the car is running too lean.

However, many XJSs with FF26 are actually running too rich. this is because the FF26 is thrown by the ECM from feedback from the oxygen sensor. So if the oxygen sensor is reading correctly, the car us running tto lean which could be a number of things, including intake leak or exhaust leak. However, if teh car is running normally but the oxygen sensor is at afult and thinks its running too lean, the ecu will try and compensate, and potentially overfuel the car and it actually runs too rich.

So see if you can work out from the spark plugs, exhaust outlet, smell etc if the car is running lean or rich. If lean, look for intake leaks at the manifold or post-MAF intake. Also remover the manifold cover and look for a tiny crack in the exhaust manifolds (look very closely and also look for a soot stain on the underside of the cover). If it's running rich but still throwing FF26, consider testing / changing the oxygen sensor.

Paul

 

Thank you for the advice. I will check the items etc. you suggest. Also, about the fuel smell, I mentioned in my first post could this be a result of an exhaust gas leak? Also, the XJS has a rough idle and only smoothes out above 1000 rpm.

 

How old is the oxygen sensor. I’m always bewildered at peoples hesitation to replace this wear and tear part. It’s supposed to give you 50,000 miles. Often times it will last longer.

if you have fueling issues and don’t know when it was last replaced, I’d start there.

 

Will that cause the rough idle and the exhaust/fuel order?

 

Sure can!

 

Thank all of you for your advice. I now have a good idea as to what may be the culpert.