If have a 1992 Audi 80 2.0 with a Single Point Injection unit. It recently develeped a problem starting. There is a blue cable on the right hand side of the engine, above what I believe is the exhaust manifold, that plugs into something (not idea what it is). If this is unplugged it starts without any problems. With it plugged in the problem returns. Can someone tell me what this is and is it easy to replace?