I have a 90 n/a z32. It wouldnt want to start so I had a friend pull the codes for me. The Crankangle sensor circuit, key cycle failure, system 55 ok was what came up. So i clean the crank angle sensor plug and the car started. The thing is it won't idle, I can drive it around but if i come to a stop without feathering the gas it will stall. Any ideas on where to start looking? Is this a common problem?