Sam when I removed mine I cut a piece of paper gasket to cover the holes completely and then bolted on the block off plate I made. I saw no change in idle after.
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Jason C, if you're reading this, post a photo of your engine bay and put Joe to shame.

 

Damn, that first bay looks like crap.

 

Heres mine. I think its pretty good, still missing IC pipes. Technically I have the pipes, but my couplers are locked up in a Jewish organization thats closed on Saturdays.

 

Here's my cluttered-but-clean engine bay...

 

Your parent's garage?

 

heres my dirty engine bay, dont worry Ill have a turbo in there soon enough.

 

shaped groove is only on the valve itself, block is flat iirc. i used silicone to seal it.

 

^Gotcha... like some black RTV silicone like I use on the valve cover humps.

 

But what about AC? My air valve has been replaced with a block off plate as well. It idles OK, but it dies when I switch on the AC. What would normally bump up the idle to compensate for the compressor? For those with MS (or other EMS), what do you do to keep the car from stalling while idling with the AC on?

 

i have no issues idling with a/c. its the CLT temp that dictates whether or not the valve is open, that's it. otherwise the stock ecu controls the idle valve itself, which should compensate for the extra load by the a/c...any chance you severed the small wire into the a/c compressor? this lets the ecu know the a/c is on.

 

Hey Scott, Any chance you have a pic of said wire? On my compressor I see a wire that goes to the fans and another that goes to the compressor clutch.
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What type of injector inlet/manifold is that ?
I hate the standard 'curved' one as it's always a strain to get a coupler onto it. Has a habit of popping off to.

 

you mean the elbow coming off the throttle body? It's a FM piece.

 

standard 2001 manifold and throttle body.


hooray for scott and his camera!

 

I'm dumb, im thinking of the P/S wire. either way, when the a/c relay is triggered the ecu should know and adjust the idle accordingly.

 

Eh?

In all the Miata wiring diagrams I've looked at, the one wire going between the A/C compressor and the ECU isn't a sense line telling the ECU that the A/C is on, it's a control line going from the ECU to cause the A/C clutch to engage.

All Miatas from the 1.6 to the NB are pretty much the same. The "safety" switches (refrig pressure and temp, etc) very from year to year and the NBs have an outboard "AC Amplifier" but logically here's how they work:

1- The user pushes the A/C button on the dash. Assuming the interior fan is on, this sends a closure to ground to the ECU, telling it that the user requests A/C.

2- The ECU then puts out closures to ground on a couple of lines, which cause the A/C Clucth relay and the fan relay(s) to engage, thus turning on the A/C.

So, the ECU doesn't need feedback to tell it the A/C is on, as it's the one that commanded it to turn on in the first place. In fact, when I had the stock ECU and EMU in my car, even after the entire A/C system was ripped out, pushing the A/C button still caused fastidle.

Perhaps you are thinking of the power steering pump? There is indeed a pressure switch on it which tells the ECU whether the PS pump is placing a load on the engine. (eg: turning the wheel while stopped).


Edit: Beat me to it while I was researching wiring diagrams.

 

So what would keep the idle up when the a/c is on? I thought it was the IAC.
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Yes, it's the electrical IAC, which is separate from the thermo-valve that's being discussed here.

With a stock ECU, it senses the A/C being turned on and raises the idle setpoint. With an MS, it reacts to the dip in idle, and tries to compensate for it by scaling up the IAC.

Either way will work without the thermovalve. It's only in the picture when the coolant is stone-cold. The problem you may face with removing it is that your idle and starting may suck slightly more when it's really cold outside.

 

Ok, so if my idle dosent correct with the a/c on is it safe to assume my IAC is no good? I have unplugged it with the car running and nothing changes. Is there anything else that could be bad? I ask because I have tried 3 different IAC's and still have the same problem.

If anyone prefer I start a new thread just say so.
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