Low MPG

[ZerokoolRCZ]

OMG this engine, seems like every week I'm reporting something on here,
The other week I had come on here with engine light due to P0087 High Pressure fuel circuit pressure (pressure to low) was able to clear code with Carly, but has come back, now both fuel pumps got changed 2 years ago, so don't know if could be a fuel filter issue? but have seen that you have to drop fuel tank to get to it

Since this fault I have seen the MPG go down, even after deleting the code, I normally get around 40mpg on average going to work, now its down to 28mpg, any idea as to what could be the issue? I have read that a faulty MAF sensor can be a reason.

Any ideas?

Thanks

 

[EddieJ]

Only throwing a few thoughts out there.

OBD based,
Take a reading of your fuel pressure to know what it is actually at, if it’s stable, low or high etc. about 700+ psi is decent.
(nb: recon pumps have been mentioned on here as having 10-15k mile lifespans, don’t know if you went new or refurb).
Read the long term and short term fuel trims, and the stoichemetric value to see if the lambda sensors are working effectively and they near match each other. If all over the place as if they are trying to matching to something could be a sign of injector issue or incorrect fuelling ratios.

Visual and physical checks.
Check for vacuum leaks, vac solenoid is at the rear of the engine below the inlet manifold and follow the pipes as best as possible.
Also check for air intake air leaks, charge air cooler etc that may be getting in unmetered, the pipe as it meets the turbo from the air box has a tendency to split over time/age.