Hello. I have a 2005 x type 3.o awd. It has an engine light on and misfire codes on 1,3,5 cylinders. It will hard misfire at 3000 rpm under load and buck and jerk. NOW, here is the odd thing. When the fuel level range is at 40 miles or lower, the engine misfire stops. The engine light won't flash, but the car feels like it surges down the road. I have been a mechanic for around 27 years and never came across this problem.

 

Welcome to the forum,
I've moved your post to the X Type tech section.
Don't forget to post an intro in the new members section.

 

First easy point to check is that there is no split in the PCV hose - the 1 inch or so dia hose that runs from the front cambox cover to inlet manifold. It's notorious for wearing through where it passes over a thin plastic support point.

Other air leakage possibilities are splits in the main air inlet trunk between the MAF and the throttle body or broken vacuum lines to the brake servo or purge valve on the firewall.

 

wtfdidido: Check for engine oil in the common spark plug well for cylinders 1, 3 & 5 (the firewall side). This is a common problem on our high mileage X-types. If you find oil around the spark plugs, remove the valve cover and replace the inner gasket. Clean residual oil from the coil boots using a little IPA, or replace coils with boots damaged by the oil or arcing.

Damage to the catalytic converter can result if the misfiring isn't fixed.

 

Thank you all for the advice. Any ideas on why the misfire clears up with low fuel level? Thanks!