Chasing random miss in an 06

I've been chasing a random miss in my 2006 for quite some time now and I'm at a dead end for where to look next. Every once in a while it'll have a light hiccup I guess you can call it in gear at idle but most of the time it happens on the freeway cruising. It could be that I just notice it more often when cruising the freeway since the engine sits at a constant rpm and any change or variation is easy to detect. No large puff of smoke that I can tell and it's never constant or grows better or worse with temp. I'm convinced it's electrical.

It has a set of brand new exergy injectors in it along with new crossover tubes (torqued to cummins spec) that only have 8k miles on them by now and were always filtered with 2 micron filters. Valve lash was reset when injectors were installed. I ohm'd out injector solenoids and everything checked fine, tested the solenoid harness and one wire seemed to take a while to find zero so I replaced it for peace of mind. Checked all connections going down to the ecm and cleaned them along with adding dielectric grease. I also checked and cleaned all the ground cables. I've tried running on my stock tune along with all other tunes from my tuner (efi live) and it still persists.

I'm at a loss for where to look next. I used to daily drive the truck but now it just sits and I'm tired of not being able to drive it. Thanks for your help in advance.

Jared

Had a buddy with a similar problem his would just miss at random times. We tried data logging it an when we would catch the problem on the log it showed his rail pressure dropped to zero. So we started into the fuel changed rail sensor/fca/tuning nothing helped. One day his alternator took a dump put a new one on an the ramdom miss left with it. Not saying that's your problem but maybe its something you can look into. To this day have no idea why in his log it was only showing rail pressure drop for a split second but sometimes things just cant be answered.

Any codes? I had an issue like what you described, had data link lost communication and fan hub codes. Wound up being a loose terminal in the fan hub connector.

I second the fan clutch issue, I’ve seen it here at the dealer once. Once. Something about the 5volt sensor reference shorting out intermitantly and pulling down that 5volts across the board for all sensors causing a hiccup.

I'm going to look into the fan hub clutch. Was there just a loose connection or a damaged wire in those cases?

The truck is currently not throwing any codes that would make me suspect anything. Grid heater was removed and that's causing a low circuit voltage code for the grid heater. I'm also getting a water in fuel code because the sensor is out and it's been raining here the last few days. Ever since I installed the dual cp3's I've gotten a rail pressure sensor circuit performance code but I've never had issues with rail pressure dropping or being sporadic so I've left it alone.

I drove the truck for a half hour last night and took it to work this morning and it hasn't had any hiccups but I know that could all change on the way home.

Had a buddy with the same problem, first he found 2 wires in the injection harness that had rubbed through, second he was also running a BD boost fooler and as soon as he took that out the miss went away.

My 08 had a quick glitch at idle and you could feel it if running 55mph in a tall gear. Ran that way for about 3 months then the alternator went out. Changed alt and hasn't done it sense.

can you take a video to share? does the RPM or gauge cluster do anything funky when it hesitates?

WUnderwood said:

can you take a video to share? does the RPM or gauge cluster do anything funky when it hesitates?

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I will if I can catch it missing a few times. It's been raining here though so if I take a video you may not even be able to hear it. I'll see what I can do. I haven't noticed the gauge cluster do anything odd but I'll keep an eye on that.

My coworker had shorted wires at the external injector harness connector. Also check the fan wiring for shorts. You can also grab harnesses and shake them to try and duplicate the miss

Sent from my XT1575 using Tapatalk

Also check the wiring down by the AC compressor. That has been known to short out the 5v ref.

Just drove it home and it missed terribly for a section on the freeway. Every time it missed it would puff out a black puff of smoke, I had never noticed before but my brother was driving home right behind me and saw it. Gauges weren't doing anything odd, no codes, the rail pressure dropped about 2k when it popped then would pick right back up but I'm guessing that's because the engine stumble or miss. I'm going to take another look at wiring tonight.

Last night I inspected the AC compressor wiring and wiring around it. The wires to one plug had the coating chewed up so I peeled it all back and checked the wires, everything was okay, and re-wrapped them. As far as the fan hub wiring I found the plug down by the crank sensor and unplugged it, checked all the pins and cleaned them and made sure it was plugged in tight. Is there somewhere else it plugs into up by the actual fan clutch? I also let the truck idle as I wiggled around the injector wiring harness and couldn't get it to hiccup any. If I knew replacing the alternator would fix it I'd do it in a heartbeat. As for right now though I'm still scratching my head.

I took a video yesterday when the truck was missing on the way home from work but conveniently all you can hear in the video is road noise...you can't even see the tach jump around or anything.

You can leave the fan unplugged and see if it still bucks too.

On mine if you stared at the voltage gauge you could just barely see it flinch just a very slight amount right after the engine would miss or glitch. Almost so slight it was hard to see but would just drop like half the width of the needle.

Most parts places will test a generator for free.

Are these truck really that sensitive to voltage drop outs/spikes? I'd be doing a loaded voltage drop on all my battery cables, 200mv is the threshold for GM, I'd assume very close to that for Ram.

Make sure all your grounds are clean and tight!

59turbo said:

You can leave the fan unplugged and see if it still bucks too.

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I will give that a try tonight and that way I can eliminate it being the fan clutch wiring, up to the plug of course.

jasonc said:

On mine if you stared at the voltage gauge you could just barely see it flinch just a very slight amount right after the engine would miss or glitch. Almost so slight it was hard to see but would just drop like half the width of the needle.

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I didn't pay too close of attention to the volt gauge but even so since I watch it on my edge cts2 maybe it happens so fast that the sampling rate of the edge isn't fast enough to show it. I'm about to throw a new alternator on it to eliminate that as well even though I don't like potentially wasting money.

To update this,
I took the truck out early this week and really watched what it was doing. The miss was worse and more often than it had been and it allowed me to really watch the gauges. I found that my rail pressure is dropping sporadically causing the miss. I'm assuming this is a bad rail pressure sensor but I will be redoing and checking a few things on the fuel system to make sure it gets fixed.