curly

iTrader: (25)

Or a 5th option, you could buy the water proof pro and wiring harness here:

https://www.diyautotune.com/product/...iring-harness/

Then rewire the entire engine, eliminating any dash harness that may be causing you issues.

As far as I know, the stock engine harness relys on every harness, dash, chassis, battery, and obviously engine harness to run. Without any one of these, it has issues. Now the dash harness might only have to do with tach and immobilizer for the stock ecu, but with the above DIY wired pro, you'd only be relying on the rest of the car for power.

NBoost

I understand the push for a new, better EMS. But have we even confirmed that the 420c is malfunctioning? The original post sounds like a complete master-f*ck of wiring, and with no "conclusion" that you have traced every wire and verified continuity from ECU to sensor on every input/output, its hard to say 1100 bucks on an MS is going to help your intermittent problems. While it may give you a way to "test" those input/outputs, I would still verify they are correct without the MS, then proceed with MS things.

Leafy

iTrader: (1)

That was going to be my suggestion. IMO its easier to just rewire the engine for a standalone harness than trying to go wire for wire in the stock harness. I'm not sure how many people have had a stock miata harness apart but I swear it was designed by either 4 people who hated each other or one criminally insane person.

mr_hyde

iTrader: (4)

The 420c might not be the problem but it is so married to the existing harness that they are a matched pair. I would never try to integrate a different ECU into this harness and I would never cut up a new harness to pair with the 420c. The adapter harness is suspect already and is a third variable. Regarding the OEM engine harness (for the NBB and Mazdaspeed at least), connector X-04 is where it integrates into the 'Front' harness and branches all over the place from there. The factory wiring diagram doesn't identify the pins on X-04 so I took an hour today and made a table of what they do compiled from 8 pages elsewhere in the wiring diagram wire by wire, color by color.

I identified about a dozen of the roughly 42 wires at the plug that need to be connected to the car in some way. Four of those insert power into the engine harness that originate at various gauged fuses in the OEM configuration to power injectors, coils, etc. Some are inputs not related to the engine harness bundle like the clutch and neutral switch - not critical for spark and fuel but necessary for proper function. There are a few that go out to the OEM dash I won't bother with (need to figure out where things like the tach will trigger for example). A bunch of the wires will be unused for my purposes like the alternator control (NA8 alternator) and the narrowband O2 sensor circuits. There are a couple of grounding wires and a few I just need to look at more to determine exactly what I'm doing with them.

I thought about reaching out to Brain on building something custom but I'm sure he has a backlog this time of year and I want to get things moving. At this point, removing the existing hacked up harness and laying an unmolested harness in that only has modifications to the needed wires at the X-04 plug is probably my best shot at removing variables. This will also allow me to re-do some other things that were not done correctly the first time and may have contributed to damaging components inside the 420c. This is a necessary first step no matter what ECU gets plugged into the harness IMO. Once I get the car running stably, I'm sure I'll get the bug to f*ck it all up by removing 'unnecessary' wires again. Been there, done that.

This is a very basic table of the wires on the X-04 connector in 'book' order (left to right, top to bottom). I haven't double checked any work and it may not be complete.

Arca_ex

iTrader: (2)

So I guess I'll make a post to subscribe.

After reading through this I feel like all of the issues could just be from a wiring clusterfuck like NBoost thought as well. I mean the 420c is a very capable budget unit, but then again most people would probably put me into the "Adaptronic Fanboy" camp. I have an e440 Select PNP that I run in my 1994 track car and have not had a single issue with it and does everything that I want it to.

That being said I have a completely unmolested harness. Not a single wire cut. Every person that I've seen locally that has tried to remove wiring for the sake of weight savings, has ended up with electrical gremlins and issues. Then again I still have to add ballast to my car to make minimum weight so cutting up the harness for the sake of weight savings is a moot point for me.

My best suggestion is a new, known working, unmodified wiring harness. Other than that I don't have much to add but I'll be following along since I'm interested in what comes of this.

mr_hyde

iTrader: (4)

Yeah, I don't have any axe to grind with Adaptronic. It has been fine for years. I feel like most of these issues are self induced when I tried to clean up the NA6 harness sections that were not needed and do most everything custom. I did remove 14 pounds of wires from the car. 13 pounds, 12 ounces would have been the perfect amount - the trick is finding which 4oz should have been left!

mr_hyde

iTrader: (4)

I was just wrapping the saga up on the MSM site and figured I'd man-up an confess the clusterfook that got me here. In short, I reversed the intake/exhaust cam gear and while the mechanical timing was fine, the CAS didn't have a trigger. What I'll never understand it how the car turned 9 laps at the Ridge the end of September 2015 before crapping out loading the trailer later that week. The long version is in the thread in my signature if anyone cares. The short version is that the car is happy, a new Adaptronic Select ECU is in right now and a 2.7 Hydra is on the shelf ready to install over the winter so I can put the Select in the street car like I always intended. I'll be at MRLS in the A group, driving a car that looks like it belongs and hopefully has enough WHP to stay out of the truly fast guy's ways...