My 2011 XJ 351 5.0 has the following issues. I got a misfire on bank 2,4,6,8 and replaced injectors on that side, spark plugs, and ignition coils. I also had a cat code on bank 2 beforehand. After clearing the codes and driving. The car would sound as if it wanted to take off fast but started to hesitate when putting a Lil foot on the pedal. Then BOOM! CEL came back on with the same codes. Would that mean my catalytic converter is bad? Also, I get poof fuel mileage like around 16 mpg.

Second issue!!! COOLANT SYSTEM!!! 😡🤬....I replaced my thermostat housing and I also bleed the cooling system. After doing so, I allowed my car to idle. It idle for about an hour. I can hear the fan running at normal speed with the heat turn on high. At that point I take her for a test drive. Temp hand is good until I stop. That hand creeps past normal running temp to about 3/4 of the way to the red line. I turn the heat on and rev the engine and start moving and the hand returns to normal. I get home and park and without turning the engine off, it sits at normal temp at idle. Also, my ac blows cool for a min then it’s room temp. Would that be an issue with my AC condenser or cooling fan or radiator? Top radiator hose gets hard.

 

I’m not sure whether I personally will be able to help you diagnose these issues, but some additional info will definitely help everyone in their efforts to help.

Could you please list the recurring codes again? I have forgotten what they were. Are the misfires still there? Is there a cat code?

For the coolant temperature, do you have a OBDII scanner that will tell you the live reading of the temps when it goes to 3/4 of the gauge? Have you performed a pressure test on the cooling system yet? Also when was the last time you changed your water pump? If you changed it recently, what part number is the pump, and did you also get the newly routed coolant piping. Do you see any leaking coolant around the water pump or under the supercharger.

With this info in hand, hopefully we will be able to better help.

All the best.

 

I had an overheating issue this summer as well. While I could hear the fan at first, it turns out it was only running intermittently and eventually died. The engine was getting enough air doing highway speeds and without a lot of start/stop, but in traffic it'd creep like you said and eventually overheat. This cost me about $1300 in repairs until I took the car back from the shop who had no idea what was going on and changed the fan myself ($600 on eBay for a new one, don't go used), cleared the ECU, and have been fine since.

While this was done I changed most of the cooling system sans waterpump, including the coolant temperature sensor, coolant res, and a lot of the plastic pipes that burst when the engine actually did overheat.

 

I use a private repair shop, and the bill is usually 1/2 the quoted dealer. All Coolant issues, Shock towers, A/C, Gas leak.
etc...

 

This is an old thread, but could you explain or send some pics of where the temp sensors are? Are there 2 of them?

 

I know for sure of one, and that was on the front of the engine about midway down. Wasn't difficult to change. I'll grab a picture tomorrow!

 

Sounds good, this is on a 2011 x351 5.0

 

Yup. 5.0 NA.