Stuttering PS3 Locomotive

I'm going by memory but I agree that at first the wiring didn't make sense. You would expect the incoming hot and ground to go through the polarity switch.

 I traced the wires a couple of times and although they're not as I expected, they do go thru the switch and do the job. Unfortunately I didn't make notes and don't remember exactly how they are. Most wires go to two wire nuts for quick connecting and a junction point. You'll need to look at one with the shell off to compare. The wiring does make sense once you see how they did it.

The locomotive continues to intermitantly accelerate as if it is losing its DCS signal

That's incorrect.

First, note that the DCS signal isn't actually present except when a command is issued or the watch dog signal is sent.

Further, lack of a DCS signal does not cause any change in an engine's operation. A DCS engine that does not have access to the DCS signal simply continues to do whatever it was doing, i.e., following the last DCS command that it received. It just can't accept any new DCS commands.

Regardless, your engine's stuttering problem has nothing to do with DCS itself, or a defect in the TIU or the remote.

Could it me poor grounding from outside rails?  G

 I seriously doubt that this is a grounding problem because the stuttering persists even when the engine is pulling a long consist of cars that would provide additional grounding to the engine through other track sections.  Also, when I push a lighted passenger car through the "problem" track section, there is steady light illumination.  The only other thing that I know of that would cause stuttering is a problem with the tach reader.  However, if the tach reader was defective, the stuttering would not occur on a specific track section when the engine is in a specific orientation.  I am now wondering if the electrical environment of the locomotive could affect the PS3 electronics.  LMS

 I've heard all kinds of pondering about the PS3 in the engines. So far, my PS3 has not given me any problems and shows excellent signal response in a consist with PS2 engines.

 I have seen many engines that are picky when it comes to problem areas in a layout. Some will find them much quicker than others! I just bet there's a problem there.

This engine has a 2R-3R switch so the engine could be missing good conductivity, especially since you had a wire off.  Why just this section of track is still the mystery. G

 maybe lay the engine on it's side and test the different points for conductivity?

 I've had a few that wouldn't pickup power on one truck correctly. Usually just a bad wire or connection.

Thanks GGG and Enginear-Joe for your comments.

I have checked the engine trucks for conductivity.  There is conductivity at different points except that I noticed sliding the axles side to side does affect this.  There are some axle positions where it is more difficult to detect conductivity between opposite wheels or different truck assemblies.  I doubt that this would account for the track-specific nature of the stuttering problem.  I am thinking about replacing and rewiring the affected track section.  LMS   

If moving the axles changes the resistance reading, I'd consider trying something like DeoxIT D5 on the axle to see if better conductivity will help.

I sprayed the axles with deoxIT D5.  No improvement in performance.  Next step is to pull up the track section.  LMS

I have finally figured out what was causing the stuttering locomotive.  When I was initially troubleshooting the problem, I pulled the shell off the locomotive and found a detached ground wire in one of the wiring harnesses.  After reattaching the wire, I tested the engine on the layout with the shell off and was surprised to see that I still had a stuttering problem.  However, the stuttering was different in that it occurred on a specific section of track and was dependent on the orientation (direction) of the engine on the track.  I immediately assumed an electrical grounding problem but testing with a multimeter did not confirm this.  Yesterday, I was running the shell-less engine on the layout and there was no stuttering.  One thing that was different about this running session compared to previous running sessions was that the overhead lights in the room were turned off.  When I turned the lights on, the stuttering problem reappeared.  It became apparent at this point that the stuttering problem was caused by the overhead lights interfering with tach reader.  The area of stuttering was also an area where several of the halogen spotlights were directed.  I report this because I have not seen this (i.e. light interference of tach reader) discussed on the forum.  Thus, I fixed one problem (reattached ground wire) but artificially created a new problem during the testing process.

LMS 

LMS,

Very interesting find.  Thanks for the follow up.

Interesting, so it works fine with shell on correct?  G

Yup!   LMS