we have a optima infinity 2012 automatic model. It’s got quite a bit of miles on but for the past year the car cuts out, especially while driving long distance. Sometimes it just slacks back. Like air is coming through the gas pipe. For a split second the check engine light comes on, and then the engine cuts out. The radio still plays, aircon still running (but no cold air). We have to stop, put the car in park, switch off and start again. We have tried everything. Service, major service, we have taken it to a mechanic that put it on a computer, but he can’t pick up anything. Changed the spark plugs, cleaned all filters. Any advice? Is anyone else experiencing the same? We are trying to sell the car but want this issue sorted out first.