Warning: Before you add MS to your 93 Miata...
 

Make sure you don't have a California 1993 car. It's easy enough to check and will save you lots of troubleshooting and irritation down the road. And it might save your engine.

A little background: I just determined that my 93 is a California car (see thread here) when I went to replace my stock AFM with the GM IAT. If you try to remove your stock AFM you will likely figure this out right away, but if you keep your stock AFM it may not be obvious. All the writeups I used for making my MS have the standard 90-93 wiring shown. As a result, I didn't wire up the extra two injector wires on the California cars. I have been running MS for months (with my stock AFM) with the MS controlling injectors 1 and 2 and the stock ECU controlling injectors 3 and 4. The dangerous part was that using my wideband readings and AFR tables, VEAnalyzer kept pulling fuel trying to lean out my base map, but it was only really pulling fuel from 1 and 2 running these cylinders very lean in order to lean out the AFR which is data from all 4 cylinders. It finally got to the point to where VEAnalyzer was outputting fuel maps so lean that they caused the car to buck (so I kept my last good map and ran with it). I can only imagine how lean 1 and 2 were running at this point. To give you an idea, once I wired the other two injectors to MS and drove the car with that same map, my wideband was showing 19:1 or so (with warmup enrichments). I immediately switched back to the base PNP map.

Just to reiterate, you can determine if you have a California 93 car by checking the ECU at pins 2Y and 2Z for a Green/White and Green wires, respectively. If you don't have your ECU handy (as I didn't), you can check the emissions sticker under the hood. Mine said something along the lines of "Legal for sale in California and all other states." Of course I'm guessing all 90-92 Miatas say this as well.

If you find you do have a California 93, just wire the injectors the same as the 94-95. Hope this helps someone.

Whoa, back it up, spanky. You seriously thought that was a good idea? And then people wonder why they blow up engines.

He didn't think it was a good idea. It was an accident. He didn't realize that his car (unlike most 1.6's) has four separate injector channels, so he wired it per the non-CA schematic.

It's fixed now.

Exactly what Joe said. I'm trying to help others not make the same mistake I made. All of the writeups for 90-93 Miata wiring do not take into account the exception for California 93's. I just wanted to help make folks aware that following the writeups to the letter on a California 93 will result in MS only controlling 2/4 injectors.

MSPNP (I believe) is wired to work correctly for Ca and Non-Ca 93's so this only applies to those making their own harness.

Yes, all the current production ones have it. A couple early ones were not set up on sequential cars but I believe all the ones from that run that found their way onto '93 CA cars have had this fixed.

I was one of those people who had a 93 miata in california...when i got the mspnp...it was acting all funny..so i took it to a shop near by and lost $ 95 bucks to find out what the problem was...send it back and got it fix....

So this is only year-specific to the 93 Miata?

'93 California cars only.

The Megasquirt has two injector drivers.

All '90-'92 Miatas, and non-CA '93 Miatas were also originally wired for two injector channels, with injectors 1 & 3 paired together on channel A, and injector 2 & 4 paired on channel B. They're wired in parallel, so only two injector wires go to the ECU.

The '93 CA-spec cars were four-channel from the factory. Each injector had a separate wire to the ECU. This makes '93 CA cars unique among the 1.6s, which are otherwise identical from an ECU standpoint.

In '94, all Miatas got the four channel injector config.

To wire a '93 CA or a '94+ to a Megasquirt, you just pair the injectors together like they are on the earlier cars.


So to answer your question, no, it's not year-specific to the '93 per se. The problem is that while "everyone" knows that the '94 and later cars had four channel injector wiring from the factory, "nobody" realized that the '93 CA cars did too until after a lot of documentation had been generated for wiring 1.6 cars in regular two-channel mode. So the first time somebody tried wiring a '93 CA car as per the then-standard documentation, it ran on two cylinders.

This was my exact issue as well. It will run and drive on two cylinders. The initial diagnosis is floating around here somewhere...

Hey, I know this is an old thread, but I just installed a used MSPnP on my '93 CA and it's running pretty weird. I'm wondering if I might have one of the earlier units that's not wired correctly for the '93 CA cars. Anybody know how I can check?

have a multimeter?

Give DIY a call? They put stickers on the various boxes to designate the changes they made along the way.

Bah. Forgot to set the fixed timing back to the map after calibration. Dumb newbie. All good now.

Right, if it's revision B or later it will definitely work for a California car.