Q: I have a problem of petrol going through to the oil sump and the car backfire and some smoke coming out of exhaust.

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When I start the car it idles ok when cold and when getting warm it start to idles rough and smoke coming from exhaust,when I rev the car it backfires from exhaust,and I can smell petrol from the exhaust.After switching it of and checking the oil,the oil is full of petrol and oil is very light because of petrol mixing with it.i have changed injectors thinking that it inject too much petrol but nothing has changed.
My car has an automatic transmission.

Hello. If your oil is being mixed with fuel then you are either getting too much fuel into the engine or you have a serious internal engine issue. Most of the time this is caused by worn out piston rings. If the rings are worn out then the fuel will bypass the rings and enter the oiling system. I usually do a compression test to verify if this is possible. If the compression is fine then I suspect that the computer is commanding too much fuel into the engine which is usually caused by a failure in the computer or an issue with one of the sensors. I use a scan tool to check the sensors first and then test the computer from there if needs be. If you want to have this fuel in the oil checked, consider getting some help from YourMechanic, as a certified mechanic can come to your home or office to [diagnose why there is too much fuel entering the engine] https://www.yourmechanic.com/services/smoke-from-engine-or-exhaust-inspection

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