Do not do any mote to the plugs etc. Your Problem and it's solution lie elsewhere. The clue for me was your bad fuel consumption and running rough. Your engine is running too rich all the time which means the ECU is unable to balance the fuel air ratio. You do not state what year or model your car is so my answer is a bit generic but should help point you in the right direction. Also have any diagnostic codes read out at the dealer or Autozone. 1) Coolant temperature sensor - if this is faulty the ECU will assume that the engine is permanently cold (as in start up mode) and set long injection cycles. The engine will permanently run rich under these conditions. Check out the coolant sensor wiring, it's connections and the sensor itself. 2) MAF mass air flow sensor - on most cars this sits on collar immediately after the air cleaner/filter on the air ducting. If this dirty or faulty the ECU may assume that more air is entering the vehicle than there actually is and tries to compensate by injecting more fuel. 3) IAT inlet air temperature sensor - located with the MAF. If this faulty the ECU may cause the engine to run rich. 4) Oxygen sensor(s) - these are located on the exhaust manifold. When an engine reaches normal running temperatures it enters 'closed cycle' operation in which the ECU sets the fuel air mix by the signals it receives about the exhaust composition from the oxygen sensors. If the sensors say there is too much oxygen in the exhaust, due to a fault the ECU assumes that the engine is ruining lean and compensates by injecting more fuel. Note that when an engine is warming up the engine is said to be in 'open cycle' and the coolant sensor signal has priorty over that of that of the oxygen sensor.
Testimonial: "great info and thanks it puts me on a different course but i think i will get it fixed really easy now and thanks again"
Thanks for the comment and vote. Just another thought and perhaps so simple I over looked this. If you have an vacuum leak (a leak in any of the tubes that connect with the inlet manifold and plenum) this can allow more unmeasured air into the system and the ECU compensates during 'closed cycle' by injecting more fuel. So just one more check is to look at the vacuum lines to the inlet plenum for leaks. These include:
Possible leaks before the throttle plate:
Air ducting connections
Positive crankcase ventilation valve/crank case breather pipe/Cam cover vent
EVAP Fuel vapour evaporation control system exits at the throttle body either at, or close to, the throttle plate
Possible leaks in the inlet manifold (after the throttle plate):
Fuel pressure regulator valve
Auto transmission in-gear hold
Brake servo pipe
Manifold absolute pressure sensor connection (if your car has a MAF you may not have this)
Exhaust gas recirculation valve
Ancillary vacuum line controlled systems
Good luck
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