Just replaced the engine in my 98. Fire right up after a little work on the timing. But its rough at high idle around 2k. Comp is telling me code P1391 (intermittent loss of either camshaft or crankshaft position sensor.) Any idea on where to start with this issue. I fear I have damage the sensor when reinstall. Replace and go from there? Or is the timing a tooth off? Any help will go a long ways on what I do next. Thanks in advance Cherokee brothers.

 

What do you mean a little work on the timing, as base timing for the 4.0 is controlled by the computer?

P1391 can be crank or cam sensor issue, but the crank sensors fails way more often. I buy crank sensors directly from Jeep; no lack of threads with people having trouble with some (not all) aftermarket crank sensors.

Be sure all tuneup parts are fresh for starters in addressing the rough running issue. Plugs, wires, cap, rotor.

 

Timing issue was I had the dist 180 out from what needed to be. I got that fixed. Every thing is new dist, rotor, cap, wires, plugs. My fear is I put a new timing chain on I might have set it a tooth off. ....the sensor was working fine before the engine swap. But who knows I might have damaged it on the reinstall. I hoping it just the sensor. Ill be busting my hands up trying to replace that today.

 

Install new sensor with no luck

 

Which one, the crank? If so, the cam sensor is still suspect. I'd test it before replacing it though. Will need a manual and a meter and the ability to use both.