I run my car in normal use in highway and no traffic I spend $20 full tank 90 miles I replace my tires,spark plugs Oem ,Transmission fluid with filter,Engine oil with filter,Thermostat,antifreeze,Air filter,replace the Ignition Coils and no codes are present I just need some good person out there that can give a good advise on this issue what will be the next procedure to correct this dilemma for this issue started a month ago and Thanks.

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Feb 5, 2018 at 15:37
  • Have you had the vehicle checked for fuel leaks? Do you ever smell gas when you get out after driving it? Commented Feb 5, 2018 at 21:25
  • No fuel leaks so far and I already check the front lines to the injectors and from the gas tank too.
    – Kiro
    Commented Feb 6, 2018 at 0:10
  • no gas smell at all? Commented Feb 6, 2018 at 19:04
  • Please provide fuel economy numbers before and after. Knowing the difference will assist with narrowing down what it could be.
    – user36139
    Commented Mar 14, 2018 at 11:56

2 Answers 2


Have you checked your intake valves? its a longshot but maybe

  • My car have 127,000 miles on it and I always use Shell gas 91 octane and I don't think my intake valves are bad and thanks for the thought
    – Kiro
    Commented Feb 7, 2018 at 14:12

Compression test the engine - if you have low compression, you will have poor fuel economy - (this is how you test for the intake valve concern the other poster metioned)

Use the OBD scan tool to check the fuel trims to see if you are running rich (excessive fuel)

A fuel injector could be leaking - causing your car to run rich - the fuel would still go into one of the cylinders, thus it would get burned. A a bad oxygen sensor could also be causing the car to run rich - does the exhaust of the vehicle smell odd.

I would take the car to a mechanic if you cannot figure it out yourself soon, because running rich will damage your catalytic converter - and that will be expensive.

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