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I have a 1999 Miata with a 1997 engine (purchased as is). The engine wiring (1997 sensors) does not mate with the stock ECU wiring and as such the car will not pass emissions. Anyone know the best way to correct this? Some of the issues are that the O2 sensor is not attached, the AC is not wired correctly and the tach does not work. Please reply to the post if you can help or you can give me a call. Thanks.
Barry, 972-775-2929
That's strange. '99 head and IM flows way better than the '97. Is this somebody elses project that you bought? Assume you're running the '99 OEM ECU with bandaids for the turbo? Maybe that's why the car has a '97 engine (the '99 engine was blown)?
My recommendations:
1. '99 head, intake manifold and sensors so that the '99 wiring harness works. Plus, you'll have more power. Note that the exhaust side is the same for both engines, so you won't have to modify turbo manifold/downpipe.
2. Standalone ECU so that your engine has a prayer of lasting more than 2 months.
3. Join miataturbo.net.
I would either get the necessary parts to make the 97 motor work with your 99 harness, or get a standalone ecu and figure out how you will make emissions. Honestly, I'd pull the turbo parts, make it work on the OEM harness, then sell the car and find a 94-95 to put the parts onto. There is a killer deal on a 94 M right now on CL.
I think part of the problem is that the '99 has a lot more of the electronic controls mounted to the engine rather than the chassis. For example, '99 has VICS. The solenoids for EGR on the '99 mount to the intake manifold instead of the passenger-side fender area. Etc. Could be really confusing for a newb or someone without documentation or reference vehicles to look at.
Barry, I'm working on a '95 with a '99 engine at the moment. Opposite from your situation, but if you want to come out to Granbury and take some reference photos, your welcome to. Also, I'll bet any shop that specializes in Miatas might let you take some pictures.
There is a Haltech that was installed to handle the turbo (car has lasted a lot longer than 2 months). Alamo said that the Haltech is normally added to the car to handle the modifications but mine is a butchered system and he doesn't want to take on the job of straightening it out. Maybe the head/intake and sensors from a 99 would be the best bet.
Yes, this was someone elses project. Not sure why he used the 97 engine.
How are you planning to hook up the 99 engine? Are you installing a 99 harness and ECU? If next weekend is nice I would like to come out and take a look at your car.
The '95 coils and CAS were installed on the '99 head. Everything swapped over OK. I have a Megasquirt and will run the VICS from one of its digital outputs. That will be separate wiring since a '95 didn't have VICS. I'm thinking you can do the same with your Haltech -- that's a decent ECU.