Earlier this year, I purchased a used 2005 Toyota Corolla sport model. The car initially seemed flawless and had undergone thorough inspection by mechanics, as my knowledge about cars is limited. However, about a week or two after adding a catalytic converter to enhance emission reduction and fuel efficiency, I began encountering issues with the vehicle.

Initially, I noticed excessive smoke emanating from the exhaust, which was attributed to the O2 sensor. I replaced the sensor, but the problem recurred within a couple of days of light usage. Returning to the mechanic, another O2 sensor replacement was undertaken in the hope of resolving the issue.

Unfortunately, the problems persisted. I observed diminished power during acceleration, frequent misfires, and consulted my mechanic about these concerns. Their response was that I should adjust my expectations, as Corollas are not known for being overly powerful.

Adding to the turmoil, the car's timing went awry just two days after the sensor replacement. This led to a series of repairs, spanning from timing adjustments to addressing issues with the oil pump, cylinder head, and timing chain slack. Eventually, these repairs seemed to restore the car to working condition.

However, the vehicle's problems persisted. It continued emitting black smoke, burning through O2 sensors, exhibiting vibrations when the AC was turned on, and consuming an excessive amount of fuel. All of these issues emerged within a mere three months since I acquired the car, leaving me deeply frustrated.

I sought advice from various sources, including a reputable mechanic who suggested that the issue might lie in the car's brainbox (ECU). Nonetheless, conflicting opinions have arisen, with some arguing against this diagnosis.

The accumulated stress from spending a significant amount of money on repairs without lasting solutions has left me weary and unsure of what steps to take next. At this point, I'm desperate for an accurate diagnosis that will guide me toward the right repair path. I had initially intended to use this car for my business, but I haven't even been able to rely on it for everyday use, let alone launching my business endeavors. Any assistance you can offer would be greatly appreciated.

Kazeem done put hand for the car.

After you install the catalyst was there any improvement with your fuel?

If the answer is no. You might want to remove it.

Sometimes when mechanic tempered with engine it don’t always remain the same again.

Your exhaust flow might be too restricted.

Op for the black smoke and vibration when ac was turned on. check all your nozzles, coil and plugs.

You already have an answer to your car’s problem. Take out the Chinese knock off catalytic converters you installed in there first

After all the English, have you scanned this car?

Your plugs are bad..some wires might be sparking against the chassis. Bad maf air flow meter....Black smoke....poor gas mileage. Are u sure they put catalyst inside it or its just mere iron mesh disguised as catalyst.....lastly if u want to buy 02 sensor.pls and pls buy brand new from aliexpress. Don't buy tokunbo. 02 sensors are like plugs ,dia life and death is based on mileage. Car wohala no be here esp when u got quacks handling it. Buy obd2 scanner wired.30k and scan.. also service your nozzles and plugs and check your fuel pump too. Those 3 if they are not in order.na black smoke.hope car not burning oil

Lets see how we can fix, message me on WhatsApp 0809275743eight