When I have car on P I hear RPM going up and down up and down. When I am driving it like hesitates. It like goes out of power for 4 seconds. Other day I was trying to make a left and I was like without power almost got into a car accidet. I was lucky it regained power 4 seconds later. I changed Engine Hardness, and MAF. The mechanic said it needs a tune up. I changed Spark Plug wires, and Spark plugs. I still get the same thing. Can it be coil?