Missing CAM or Crank sensor signal P1391

plymouth
voyager

#1

My parents have a 98 Plymouth Grand Voyager Van 3.3L Flex Fuel engine. The van is in really good shape and has around 80,00 miles on it. We were driving the van on the freeway and it started to have a slight misfire. The next day I was driving it on the freeway again and it really started to misfire. The check engine light came on and a P1391 code came up. We have replaced both the CAM and Crank sensors now. I cannot see any problems with the wires or connections. I have looked at the signals on an oscilloscope and they look fine. Now the van misfires so bad it cannot be driven . I need some help! I have done some reading and have seen a comment that the CAM chain may have jumped a tooth. Is there anything else that could be wrong. Do you need a special scan tool to time the engine to new sensors? Thanks for your help.


#2

Click on this Auto Zone web page, and click on Fig. 6 http://www.autozone.com/az/cds/en_us/0900823d/80/1a/46/ba/0900823d801a46ba/repairInfoPages.htm. Using a digital multimeter, ignition key in RUN, check the wiring, power and signal, from the cam and crank position sensors to the power supply wire, and to the engine computer. Check the voltage while shaking the wires (A thin back-probe can slide under the Weather Pack and touch the metal part of the terminal). Turn the ignition key OFF. Disconnect the battery. Disconnect the connectors from the engine computer AND the cam and crank sensors. Connect the multimeter to each end (at the computer, and at the component) of each wire, and watch the ohms reading while shaking the wire. If the ohms vary, the wire needs closer checking./// Yes, if timing has gone out of whack, an engine can misfire, and backfire, badly. You’ll need to see the position of the camshafts, and the crankshaft, to determine if timing has jumped. To do this, you need a repair manual.