Changed plugs, wires, cap, rotor, and coil, also treated fuel tank and changed fuel filter 3 times to eliminate contamination but the vehicle is still running poorly.
My car has a manual transmission.
Hey there. You should take a fuel sample in a clear glass container, and then if you put the container in a freezer, it will separate the water from the fuel and you will see if you have a lot of water in the fuel.
If there is water present, then you will need to remove the fuel water contamination. If there is no water and gas is not contaminated with anything then you will need to have the engine computer tested for running codes to see if the EGR valve is stuck open causing the rough running engine.
If the EGR is stuck open, it will cause a rough idle to mid throttle but run good at higher RPM's. If the EGR is not stuck, then the fuel injectors would need to be checked for flow causing one or more cylinders to run too lean from previous fuel contamination. If this is the case, then you may need to remove and have the injectors cleaned or replace them with new ones. For a precise diagnosis, consider YourMechanic, as a certified technician can come to your home or office to inspect the rough running problem and follow through with repairs.
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