CAT C15 /6NZ trouble continues

The speed sensor cant cause a misfire/ stumble. The most it can do is if you have no speed signal the engine will run at the setting for max rpm with no speed signal. If you are worried about it pull the speed signal pins out of the ecm and drive it off your phone gps. Probably will drive the exact same. Toggling the splitter when stopped is a coincidence the shudder stops. Nothing connects the two.

 

I was thinking about your speedo jumping while in neutral, range switch toggled, and sitting still... I know I have seen this before. In times of trying to find those hard to pin point vibrations, I have put trucks up on jackstands and ran it up to the vibtation speed and observed. Seems like when a truck is in this condition, totally free with no brakes set and not pushing a load or a load pushing it, if you are sitting still and toggle the range selector the speedo while jump. My theory is that is just the quick movement of tailshaft when it makes the range shift. If you ever have had a transmission on a bench and range shift it, you have seen how much the tailshaft rotates and it does it quick. This is my guess on why your speedo jumps sitting still. Now going down the road, this would not apply. No range shift would take place until detent for slave valve kicks as you pass thru neutral. My only theory is when you are flipping range selector going down road, you slightly let out of foot pedal and change the pulse width to the injectors and your miss disappears... If ECM was seeing this speed rapid increase, it would de-fuel when it hit whatever limit your foot pedal is governed at. Just disconnect the speed sensor and see if "pop" goes away. Easy way to tell if they are related.

 

Talk about gremlins. On the ecm I would ask around and consider quality rebuilt or maybe even used. I would try Mr. Haney. Your splitter situation is way over my head but the speed pick up sensor is is that equation. I would remove it, clean off the tip, and be sure to reset it at the proper depth. Try a new sensor. Does this happen both with your ecm and your man's temporary ecm?

Not to scare you but just a story on new. I had a 95 Pete with a 5EK. It was during the time when 5EKs would get weaker and weaker over time after about 100,000 miles. With the cruise set, then turn it off for whatever reason, press the accelerator and I would get a bang as the ecm put fuel back to the engine. Every time. I took the truck in for a reprogram by Cat to restore the power. Yup. Bang was gone. Go figure.

 

I have had 4 trucks that do that. Totally normal to peg the Speedo when toggling high/low sitting still in neutral. The tailshaft sends off some wierd vibe when you do that and the sensor picks up on it..
Heck 2 my trucks will actually log a code if you keep doing it..
This is not a problem nor is it anything to do with your problem..

 

I've never seen. I am glad that you know it can be a normal event. I'm done learning something new for the day.

 

Well it is nothing out of the ordinary for me.. I have a few other buddy's that there truck will do that too! Lol
So it' not just me..

Really tho, how many people sit at a red light with foot on clutch toggling high/low back and forth like a mad man.
Probley none.

 

A guy that is peed off and has been fighting a misfiring engine for 18 months!

 

Well I can't argue that. !!!!

So true , so true.
Yeah he has had a bad go of it there, I hope he gets it figured out .

 

That was my exact thought but I kept it to myself. Or the nervous fidgety type. Got to always be moving something.