I took my car in and I have already had a refurb engine, and I took it back in for a really rough idle and for the RPM to go from 1000 to 500. I already had the the MSP 16 done and I took them the paper work to see if the engine lack of power was causing my rough idle and engine light to always go on and off.

The dealer said that there is a wire that is loose that is probably making my engine light go on and off and that the wire is also probably causing my engine to drop RPM and causing the car to vibrate really bad when it dips to 500rpm when stopped. Does that sound right. It was fine after the MSP 16 was done then a month later it got like this and it is worse than ever. Is it possible that some wire being loose could cause it? I dont know for sure if it is a CEL wire or not, but he said it was the one that kept causing the engine light to come on, and also a Cat error and they are replacing the cat on the car as well.