I was driving my parent's 1998 Plymouth Grand Voyager when it started bucking and the check engine light came on. I pulled into an Autozone and had them scan the Van and found a P1391 code. I did some research and found it means "Intermittent Loss of CMP or CKP" or intermittent loss of crank sensor or cam sensor signal. My dad and I inspected the wiring and sensors and found nothing wrong. I also looked at the signals with an oscilloscope. The signal does not appear to be bad or cutting in and out on either sensor. We replaced the crank sensor because that is what Autozone had it stock and it DID NOT DO THE TRICK. Any other suggestions? The van idles fine but will start missing minutes after running when throttle is pressed. We are planning to replace the CAM sensor too. I am just afraid that will not fix it. I have seen this question posted before, but there are no solutions. PLEASE HELP!

 

I think I found the problem. It looks like the timing chain was bad. 1" to 1-1/2" slop. The manual show there should be a tensioner, but there was not one when I took it apart. Should there be a CAM chain tensioner on a 98 3.3L engine?

 

the CAM sensor will fix this.. same thing happened to my old stratus.. same engine.. cam sensor went out.. not too long after that i replaced timing belt.. they are linked prolly from the bucking and kickin... who knows.. but yea...