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Unread 10-22-2012, 03:56 PM   #1
ngib159
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Crankshaft Position Sensor Problems

I recently self-diagnosed my '98 4.0L 5 speed TJ as having a bad crankshaft positioning sensor. It takes a bit to crank up and idles down to 300 rpm or so if i drop it into neutral to brake among a few other problems. I bought a new sensor but can't seem to find the part on my transmission bellhousing to replace it. Any advice would help.

In an unrelated matter, I was trying to relocate my mirrors so I could take off the doors and the painted torx bolts where the relocation brackets should go stripped out. Any advice for dealing with that would be helpful as well.

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Unread 10-23-2012, 11:30 AM   #2
CjinPA
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If you lay under the drivers side of the jeep, and looking from rear towards the front of the Jeep, the crank position sensor is at the 11 o'clock position on the bellhousing. It is held in with two small bolts. If I recall correct you need a 10mm socket for them.

As for the torx bolts you will probably need to drill them out and rethread the holes.


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Unread 10-23-2012, 11:45 AM   #3
Jerry Bransford
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Your symptoms don't make me think of the crankshaft position sensor.

The extra time the engine takes to start if the Jeep has been sitting for a while makes me think the Fuel Pressure Regulator is leaking and not keeping fuel present in the fuel rail next to the fuel injectors for a fast start. The extra time it is taking to start is probably just due to the time it takes the fuel pump to get the fuel back up to the fuel rail.

The low idle RPM makes me think more of a dirty IAC (idle air controller) which is screwed to the valve-cover side of the throttle body. The IAC is what provides all of the engine's air at idle and when it is dirty, the engine won't get enough air to idle properly.
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Unread 10-23-2012, 01:36 PM   #4
tjsean0308
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Quote:
Originally Posted by Jerry Bransford
Your symptoms don't make me think of the crankshaft position sensor.

The extra time the engine takes to start if the Jeep has been sitting for a while makes me think the Fuel Pressure Regulator is leaking and not keeping fuel present in the fuel rail next to the fuel injectors for a fast start. The extra time it is taking to start is probably just due to the time it takes the fuel pump to get the fuel back up to the fuel rail.

The low idle RPM makes me think more of a dirty IAC (idle air controller) which is screwed to the valve-cover side of the throttle body. The IAC is what provides all of the engine's air at idle and when it is dirty, the engine won't get enough air to idle properly.
This.
Generally bad CPS will result in a crank no start. Have you tried starting it after cycling the key on and off a few times to prime the pump before starting?

The torx screws on the windshield are a real pain. There are many methods to try and extract them. I like an impact screwdriver not pneumatic the kind you hit with a hammer and a top quality torx bit that won't shear as easily. I have also welded nuts onto the torx head when surrounding paint was not a concern. With yours all stripped and mangled the drill or the welder would be my next tool.
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Unread 10-23-2012, 01:58 PM   #5
BigRodney
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Cjin is correct, I’d add that if you have an automatic there is only one bolt, same location as described though. You should be able to see it on the drivers side down through the top of the engine compartment. When you change it be careful not to let the wire lay on the exhaust manifold like I did, zip tie it back to the cable coming through the firewall in that area.
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Unread 10-24-2012, 03:42 PM   #6
ngib159
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I should've specified more on the low idle/dying. It only does it from time to time, typically when its cold or raining and will sometimes idle down to turning itself off. I'll try cleaning/replacing the IAC in response to your suggestion. As for the cranking problem, sometimes it takes a tap of the gas to get it to turn over so you might be correct on that one too. Either way, I already bought a new crank positioning sensor so I might just go ahead and replace it anyway. Thanks everyone
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