zumer715

I've been trying to chase down an issue for about four months now and it's driving me crazy. I've even had it in to Jeep and they say it's a harness issue. Anyways here we go....
Symptoms
-rough running
-speedometer needle jumps all over the place when running (started after taking it to Jeep)
-very difficult to start
-seems to be misfiring intermittently
-sometimes stalls
-IMPORTANT (I think)
It keeps blowing this fuse when it quits running and I do not know why. Using an advanced electrical testing probe I've found that both of the terminals for this fuse are grounded and nothing changes with the ignition on... I am not sure if this is significant but that's what I've found.

Parts replaced
-coil packs
-injectors
-ECU
-cam position sensor (and re-indexed)
-crank position sensor
-engine temp sensor
-TPS
-IAC

Any help is greatly appreciated. Thanks guys

zumer715

Here's a video of what it does, it normally runs tougher than that and the exhaust is loud cause I disconnected it before the cat to eliminate a clogged cat as the problem

mikesignal

you might want to try and re-post this in the OEM section.

as far as the fuse blowing-my best guess-I would think you have a ground, or short causing this. Might be a frayed wire that is not making a good connection, causing the rough idle; and then occasionally the open wire is touching something metal causing it to ground out and blow the fuse. Since the fuse says ign-rail coil-fuel injectors, I suspect it's in a wiring harness associated with the fuse (obviously) which is? fuel rail? ignition coil rail? Disclaimer is I am just guessing. sorry I couldn't be more help.

zumer715

all good! Thanks for the reply.

97grand4.0

If not getting voltage on one side of that fuse, means an open, or break, in the circuit, not a short. Consider bad connection, or get the right schematic diagram somewhere and trace it out. Seems with the key on that fuse should have +12 on one side of it, unless, maybe it's being shut down by some safety system such as a rollover switch or fuel pressure relay related thing..it would be good to back probe the fuse with your meter to ground and see what the voltage looks like while running, do you see it drop out intermittently? That would tend to suggest a bad connection...hope any of this helps

zumer715

I just started opening the harness and found a spot where the wire from that fuse had melted through the insulation into two ground wires and was grounding out the circuit intermittently. I repaired the wires, plugged everything back in and she fired right up!