For the last few months I’ve had both codes, so the time has come to resolve it, so far no joy, what have I done so far, the car also has a poor idle and has got worse from year one. No other error codes. Jaguar looked at the car 3 times over the years to find the poor idea and failed. It’s now at the point it needs fixing.

changed the maf
checked for vacuum leak, used smoke and pressure No leaks detacted
striped the manifold off and replaces the O rings around the pvc vacuum pipes
all cleaned and reassembled
cleared faults, disconnected he battery, after five mins both codes back

the car runs on LPG and petrol, I get the fault on both fuels, it runs 5% petrol while on gas.

Smoke tested again, nothing,

ok, main fold off again and bit the bullet and removed the Lower manifold as well, it’s very messy, but the seals are good.

All ideas welcome, still in a thousand pieces, so anything else to check.

Thankyou for looking.

Geoff

smoke pot worked well..

Smoke can

 

I have used throttle body cleaned and with the engine running spray around the manifold and all vacuum hoses until the engine starts to stumble. It is a little time consuming but effective. On the 3.0 several people had problems with the “O” rings on the manifold using this method should help. Be sure to get a few cans you may need them.

 

Here is a video of the odb readings , it’s long but riveting not

You Tube

 

A P0171 & P0174 can be caused by many things mainly related to the mix of fuel and air. If you are without any vacuum leaks that you can find I would be looking at your injectors. If you can use petrel then add a fuel additive or pull the fuel injectors and have them tested and cleaned. I use BG44K the best I found on the market.

 

The leak can also be on the exhaust side, any air escaping between the exhaust valve and O2 sensor.

 

Thanks litteredwithfaults I’ve just disconnected the secondary air pipe from the blower and blocked it, STFTs are now much more stable and the idle is so much better. Ecu reset next, , so secondary air valve is now a possibly, more testing to follow

thanks

 

I have the same error codes P0174 and P0171 on my 2010 XF. Not sure what it is exactly but I did notice a crack in my air intake tube. Would this be the culprit?

 

Probably. The whole air intake set of parts must be 100% sealed vacuum tight.