Hello. I once made the mistake of installing a fuel saving device into the lighter socket of my mark x 300g (wanted to test out the results for use on my other vehicles). It actually messed up my car's fuel average. Threw it out after a few days but ever since, the fuel average of my car has gone down dramatically. It used to give me easily around 7.8kmpl to 8kmpl within city before testing out the fuel saving device...but after testing the device, now over the period of time it has gone down to around 6.3 to 6.5kmpl! Also, the display that shows the fuel average gives erratic readings when I fill my tank...right after the tanks is filled, the display sometimes gives readings of 10kmpl...then 8kmpl...then 11kmpl...then 6kmpl....and like that...and then after driving for a few kms it settles down around the 6kmpl mark.
Before I tested out the fuel saving device, none of the above used to happen. The average used to show a constant 7.5 to 8kmpl...and was not erratic.
I believe it to be some kind of an electrical fault...and I have been to many workshops but have been unable to diagnose it still. I think the fuel saving device actually messed up the car's ecu and somehow changed the fuel mapping values.
It's not a mechanical problem as throttle body is cleaned...cat converter is clean....manifold is serviced...spark plugs clean...fuel filter changed...I get this maintenance regularly but still the fuel average problem persists.
Please recommend me a good ecu electrician who could reset the ecu back to it's default values or give me the solution to this chronic problem.
