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Engine runs surges and stalls, unplugging cam sensor makes no difference

laxmax44

NAXJA Forum User
Location
philadelphia
well ive been trying to hunt down the cause of my surging and stalling. its only throwing one code, p1391, intermittent loss of cam or crank signal. both of which have been replaced, to no help. ive noticed something weird though. if the crank sensor is unplugged, engine will just crank and not run at all, as expected. but with the cam sensor unplugged, it makes zero differnece. engine runs equally shitty either way. and with a brand new sensor, id think it were bad wiring. but when it is disconnected you get a new code. cam sensor circuit malfunction. so it does realize when you unplug it. but it runs no different. can anyone make any sense of this? thanks

edit: its a 98 cherokee 4.0
 
You can insert the cam sensor oriented in the wrong direction on the older models. Not sure if the 1998's are the same or not though.
 
well after no luck with anything else im still thinking its the crank sensor. could there be something wrong with the flywheel? what does it actually read on there. i wouldnt be surprised if it was pretty dirty, the engine does appear to have had a pretty bad oil leak which could have gotten all over it.
 
Is it still throwing the same code?
 
yup, that intermittent loss of cam or crank signal. pops up immediately after starting.

Try starting it with the cam sensor disconnected!
 
i have, it runs the same. only it throws another code, something like cam sensor circuit malfunction.

Does it also still throw the original code, if so you just proved it is not the Cam sensor causing your problem.

Could be just about anything (fuel, spark, vacuum, O2 sensor, TPS, low compression on cylinder, etc , but the lack of other codes for your year jeep makes it sound like the CPS sensor or its wiring. Check the wiring to see if got burned getting to close the exhaust manifold.
 
no, the p1391(intermitten loss of signal) is always there, it just throws an additional one when the cam sensor is unplugged. and from what i understand, the cam sensor usually wont even make the engine run this bad. so i believe it is the crank sensor also. i have already inspected the wiring that is exposed, i guess now im going to break open all the wiring looms that it runs through. first im replacing the cps again, this time with a dealer part, i think the autozone one i have may be faulty. it shows a resistance between the two terminals.
 
no, the p1391(intermitten loss of signal) is always there, it just throws an additional one when the cam sensor is unplugged. and from what i understand, the cam sensor usually wont even make the engine run this bad. so i believe it is the crank sensor also. i have already inspected the wiring that is exposed, i guess now im going to break open all the wiring looms that it runs through. first im replacing the cps again, this time with a dealer part, i think the autozone one i have may be faulty. it shows a resistance between the two terminals.

I am not a CPS expert, and all my stuff is 85-90 era, but I have read posts about a dealer kit and TSB on a fix for a CPS problem, and something about a spacer, in this forum a while back. Might be worth searching here, but ask the dealer to do a TSB search when you buy the dealer part. Also check the fly wheel to make sure it is not missing a tooth (though that would cause starter problems). The CPS is a magnetic coil that pushes a small voltage out as the flywheel tooth passes close by.
 
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