Turned the key for the first time and the engine started up and went full open throttle and wouldn't shut off. It was very scary. Good thing the battery connection was loose. I pulled off the negative cable and it shut it off. Not sure about this one any suggestions on what might have caused this.

 

As I recall you are using an SN95 harness (Ford). The throttle is not electronic so there is really very little that could cause this other than the the throttle plate being stuck open. If the throttle plate is closing normally look for a very large vacuum leak. There are a number of vacuum ports on the underside of the upper manifold, some large enough to cause the idle to rise significantly if they are not used or plugged.

Hope that helps,
-Jason

 

I'm really sorry to hear what should have been a thrilling moment turn into a nightmare for you. I think Jason is spot on. The computer is seeing air getting in somewhere and just dumping fuel to make the mix right. It doesn’t know or care where the air is coming from, all it knows is it is supposed to keep the mix at 14.7 to 1 so it turns on the gas to do that. If your throttle plate is closed there must be a leak somewhere. Keep in mind with no load on the engine it doesn’t take a very big leak to tack it up to 5 grand. A hose off or gap in the plenum gasket would do it.

The good news is this is probably something simple and a basic inspection will likely reveal it.

 

Initially I thought it to be electrical. The throttle body is operating properly. It must be sucking air from somewhere. I will look for a vacuum leak and report back. At least I had spark and fuel!

 

I am pleased to report the problem has been solved. There were two issues. One, there was a vacuum leak (hose off under intake plenumn) and Two, the idle stop arm on the throttle was a little bent and binding up on the throttle body. Wheww! Simple fixes, The motor runs Great! Thanks for the help.

 

Hey that's gret news!! May all your troubles be so easy!

 

So you figured out why you couldn't shut it off as well?

-Jason

 

I'm still working on that. I most likely will need a relay controlled by the keyed hot to shut down the EEC ignition circuit and O2 Sensors.

 

The harness should have an EEC relay that you should be triggering via the Miata keyed hot wires (usually white with red).

-Jason

 

From the Miata small yellow plug. I connected the blue with red to # 1 on Ford brain for the permanent hot and white with red to # 57 on the Ford brain for the keyed hot. On the 95sn there isn't a fuel pump relay on plug # 27 (which you know already) so I connected the Red with green (ignition) and gray with yellow (HEGO) to the keyed hot too. Plus the jumper wire on the Miata fuel pump circut. I am planning to switch over the fuel pump to the ccrm like you suggested. The motor started and ran fine but when I turned the key off it wouldn't shut off. That is why I am thinking I need a relay on the ignition and HEGO circut.

 

I eliminated all of the Mazda wiring for the drivetrain (except the ignition switch) & wired it as a Mustang. This included all relays as well as the inertia switch. This makes it much easier to diag. a problem if one should arise because you can follow the flow charts in the Ford shop manual or use the Ford EVTM.

 

That seems to be a cleaner way to approach the wiring. I'm thinking of going that route too.

 

That is exactly my plan too. I figure the computer and wiring could care less what chassis it is in so I may as well leave it completely intact from the donor car. I'm even going to try and use the Camaro instrument cluster and cruise control system since it all runs off the engine computer. Key word there is try...

 

The EEC relay is part of the CCRM. Find the ignition wire that would have run to it and connect your miata white/red to it and the HEGO heaters.

-Jason