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Intermittent no-start, P1391

billy120480

NAXJA Forum User
Location
IN
Hoping someone could share some thoughts on this...

I have a 2000 XJ with around 140k on it. Around 125k I put in a new 4.6 stroker. Until now everything has ran great with no problems.

About a week ago out of nowhere, I start it up and drive off and feel some hesitation and the check engine light is on. I go to the store and when I come out it will not start, it just cranks. I try several times and on the 5th or so I starts up and runs like nothing was ever wrong with it.

So I go to the part store and have them scan my engine code. P1391 - Camshaft sensor or Crankshaft sensor signal intermittent. So I order both sensors.

In the mean time, when I go to start it its about 50/50 wether it starts or just cranks. Turning the key all the way off and retrying seems to usually solve it. Occasionally it will start but runs very poor and usually dies, like as if only half the cylinders are firing.

So, I get the new sensors in and change both of them out and unhook the battery to reset it. It starts right up but I get a check engine light. I turn it on and off trying to repeat the no start but so far it has started fine everytime.

I go back to the parts store and they say its the same code so I have them erase it. All was fine for a day. Then last night I start it up and the light comes on, but still no troubles with it running. It still runs great like it did 2 weeks ago.

Today I start it up, engine light still on, and I am going down the road and the engine loses power and it dies goign about 45. I throw it in neutral and start it and it fires back up and runs like nothing was ever wrong. Same code though

Im not sure what to think really? The sensors are fine, but its getting intermittent codes I guess..but it goes away when I turn it off and back on, eventually at least.

Any thoughts?
 
did u check for broken wires??mayb when the motor moves a certain way while driving, a wire will touch causing ur code/loss of power...i would check continuity from the crank sensor connector to the pcm, as u wiggle the harness around...hopefully that helps
 
well i lightly examined it, but i didnt go as far as tearing open the loom. i have a dmm, but how do i go about checking it, the two ends are kinda far away from each other to reach both. i initially thought that may be it, but just the fact turning the key on and off fixes it for a while throws me off
 
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