jealous of your engine bays
#21
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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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#30
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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?
#31
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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.
#32
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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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#37
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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.
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#38
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So what would keep the idle up when the a/c is on? I thought it was the IAC.
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#39
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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.
#40
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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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