Hey, guys. New to posting on the forum, but have read many posts.

I have a 2003 4.0L 4x4 that has 140k-ish miles. Recent tune up with new coil pack, plugs, wires and fuel filter. New battery and battery cable ends. New crankshaft sensor and the inertia switch is bypassed (wires cut and spliced together, solid clean connection).

My truck is stalling when I am driving down the road. It isnt all the time, but is very intermittent as to when it will happen. I've rechecked all the new work to see if anything is done wrong (loose wires, etc) and no luck. Fuses and relays are fine. When the engine dies, sometimes the theft, check engine and check fuel cap lights will all flicker. No rhyme or reason to what will make it crank again, sometimes it is time and other times it'll just start right up.

I have done some of the suggestions here, like checking the inertia switch and cranksensor, but those are a non-issue. Any other suggestions would be great.

 

Fuel pressure check? Check for any codes that bring on the check engine light? Sounds like something electrical.

 

So, I am assuming its not fuel. I hear the pump priming with the key turned. That doesnt mean that it isnt weak, i havent gotten a pressure gauge on it yet.

Got a code reader hooked up and nothing. no codes.

New development is that it doesn't ever crank. It just sitting flashing the check engine light, check fuel cap and theft light. The idle air control valve is clicking for some reason and when unplugged i assume it is its relay that I hear clicking still. Can't find where its coming from. The fuel pump is running the entire time this is going on. I'm kind of unsure where to head next.

 

Started messing with all the connectors again, even unplugged and plugged the EEC-V. This of course reset it and I could drive for a few miles. I had a cheap code reader hooked up and I was watching every I/M readiness system go from incomplete to OK. Not 60 seconds from completion of everything the truck stalls. Still no codes. Get it back home and now get the intermittent flickering dash lights again with intermittent starts.

 

Welcome to FTE.

Did the problem come about slowly over time, or suddenly after some event?

Since it seems to be an intermittent electrical feed problem & no trouble codes, begin with the basics.

Turn off all electrical loads & check the no load battery voltage across the battery Posts & put up the Number. This will provide an indication of the battery state of charge.

Then turn on some heavy electrical loads, like the head & fog lights, blower motor on High speed, push the cigar lighter in/on when your ready to make a reading with your multi-meter across the battery posts. Post up this reading. This will indicate if the battery can output under load without voltage drop.

Then measure under load voltage drop across the battery Cable Clamps at the posts. This will indicate how good their connections are/if there is unseen sulfation between the post & cable clamps, or the clamps are loose, causing a poor connection & under load voltage drop.

If all that checks ok, go to the under hood power distribution box & check for under load voltage drop there. This will test the B+ cable run from the battery to the distribution box & the cable run connections on both ends.

If that checks ok, try a wiggle test on the ECM power relay in the distribution box. If it wakes up, remove the relay & check for corrosion, or loose connections to the power relay blades.

If the relay connections & wiggle test is ok, try Thumping the relay to see if it'll wake up. If so, swap it for a like known good power relay not needed to run the engine & let us know how it goes.

More trouble shooting thoughts for consideration.