Jeep 4.0l starting issues

jrmiller

jrmiller

Well-Known Member
Joined
Sep 11, 2011
Location
Lincolnton
I've got a 2000 Jeep Wrangler with a 4.0l inline 6 and on my last wheeling trip to the gulches the Jeep started not wanting to idle right and when it would die it was difficult to get it started back. Later in the day I had a wire for my electric fan get pinched and arc off my fenders and the vehicle died. I got it started back and finished off the day wheeling. And I haven't been able to get the Jeep to run right since. After the Jeep has been sitting for a little while (days) I can usually get it to crank and idle first try but it almost seems like something is putting a big strain on the battery. After the first time I start it up it will crank but never actually fire unless I give it throttle and then it will run and only shut off when I let off the throttle.

Now for the list of things I've tried..

New idle air control
New throttle position sensor
New map sensor
Battery load tested and charged
Alternator tested
New crank position sensor
Did a compression test
Fuel pressure test
Drained gas and re filled with new gas

Just curious if anyone on here had any more ideas before I have a bonfire and throw the POS in it.

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Fuel pressure was fine and the spark plugs and coil rail are fairly new. It runs fine as long as I apply any throttle at all. No misses or hesitation when I apply more throttle. It really has me baffled. I'm no mechanic but I can usually figure something out but not this time lol

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The TP sensor has 3 wires. One is 5 volts, one is ground and one is the signal wire to PCM
Key on, engine off- what is the voltage of the signal wire with the throttle closed? Now sweep it fully open, slowly, and report back.

Check for chaffing on the engine harness where it wraps around the driver's rear of the valve cover too
 
Jody Treadway said:
The TP sensor has 3 wires. One is 5 volts, one is ground and one is the signal wire to PCM
Key on, engine off- what is the voltage of the signal wire with the throttle closed? Now sweep it fully open, slowly, and report back.

Check for chaffing on the engine harness where it wraps around the driver's rear of the valve cover too
Click to expand...

What I assume to be the signal wire was .95 volts with the throttle closed and open it was 3.9 volts and the wire behind the valve cover appears to be in decent shape it has loom over it still and doesn't look damaged.

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a_kelley said:
My Inquiring mind wants to know what that would have to do with it?
Click to expand...

The 5v reference goes through the clockspring via some wiring voodoo.
p0123 and/or P0121 can be caused by a bad clockspring. When the CS is corrupted, you get funky TP voltage values that cause erratic idle and hard starting.
 
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I just tried unplugging the clock spring with no change to the behavior. It started one with no issues before I unplugged the clockspring and then wouldn't start so I unplugged it and nothing changed. I don't have any check engine codes which is surprising to me

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