Hi Guys,

Just popped over from the D3 forum, hope you dont mind an interloper looking fro some advice as most of the D3 gurus run log burners.

Got a 4.4 V8 D3 running prins lpg conversion, had new heads a few thousand miles ago. Generally runs fine but slightly lumpy idle, can’t get above 16-17mpg no matter how granny like I drive it. CEL is on, codes are P0420 Catalyst System Efficiency Below Threshold (Bank 1) and P0171 System Too Lean (Bank 1).

Freeze frame data:

Click image to enlarge

http://www.fullfatrr.com/forum/topic30850.html

does that help? There is nothing that can't be fixed with a hammer😜😜
FFRR 4.4 SDV8 Autobiography Santorini Black.
KIA E-Niro 4+
2021 Discovery 5 D300 MHEV commercial

It's unlikely to be a cat issue if you are getting a lean code too.

Is it doing under LPG, petrol or both?

What are your Long term and Short term fuel trims now?
Looks like they are running rich in that freeze frame although not majorly so (it's adding fuel as it thinks it's running lean).
The lean code means it must be maxing out at some point though and the economy also suggests it's dumping in fuel.
The uneven idle also points to an induction/vacuum leak or it could be a separate issue (idle control/throttle).

I would go for an induction/vacuum leak somewhere especially if the heads have been off recently. There can be quite few places it can suck air in that aren't obvious.
A water spray can help as a basic and quick way of tracing unobvious leaks.
Also check the upstream O2 sensor signals are outputting decent info.

This video covers your problems:

Your fuel trims look OK to me....... Stolen / Gone: 2006MY Supercharged LPG Autobiography - Zambezi Silver with Sand/Jet/Jet Oxford Leather.....

Thanks.

Happening on both, currently running on petrol only to try and find the fault. ==================================
05 D3 HSE V8 4.4 LPG

CG-SC wrote:

Your fuel trims look OK to me.......