Studders at random speeds Coded p1391changed Cam sensor ran better one day now worse

Question

Sometimes it won't start at all.

Answer 1

P1391 Intermittent loss of CKP and CMP

If you have a loss of CMP (cam position ) sensor the engine will still start,will not run right  . It is the loss of the CKP , the voltage refference to the CKP is from the ECM, You can put a new CKP and try it, If this code occurs you need a ECM.