Hi All,
I am a newbie, I have now had my 1996 NA SW20 here in Perth for just over a week, & driving to & from work each day.
I have a couple of things with which I am not happy & need to get fixed. Will put them on separate posts.
First one is fast idle speed, around 1500 rpm. My initial thought was induction, so last Sunday pulled out air filter to look at that. Has standard system. First thing was that it has a Splitfire oiled filter that looked nice & clean.
However one of the clips on the Air filter enclosure is broken, allowing air to bypass the filter element. I made up an arrangement to hold the two halves together, to prevent the bypass.
Also observed an un-filled approx 12 mm hole in the upper half, (clean side), of the air filter enclosure. After reading some posts on this forum, I reckon that the hole is for an Inlet Air Temperature Sensor. I don't appear to have one. It doesn't appear to be hanging around loose on wires.
I plugged the hole with a black plastic retic hose plug. When I stated the engine, after it warmed up a little, idle speed dropped back to about 800 rpm. I thought that I had aced it, & went for a little drive.
When I started the engine Monday morning to go to work, idle speed was back up at 1500 rpm, & hasn't dropped back again. I have looked at my fixing of the two halves of the air filter enclosure, & that still looks o.k.
Another thing that I reckon may be having effect is that water temp stays quite low, unless I am stopped in traffic idling. Sort of looks like the effect I would expect if thermostat was jammed open.
I am having a mechanic look the car over on Friday, but any comments or thoughts would be appreciated.

Car is still running in cold start, due to low water temp.  Replace the thermostat and you'll be good :)

yeah fix the cooling system, they are very tempermental on these cars and takes a bit to get right.make sure whoever does the coolant knows how to bleed the cooling system of an mr2 if they havent done it before walk away, its not anything like a normal car.
 
i would also get that temp sensor fixed, its the same as the one in the engine lid, so you can pull it off there and use it in the airbox and see if that fixes the problem, if it does then just buy a used one from here and replace.
the airfilter being exposed isnt what is causing the high idling, most likely its the temp of the coolant
 
if your anywhere near the WTF auto then tristan is the best MR2 mechanic to go to. im not sure where he is located one of the perth boys can help you out with that.
 

WTF is a little north of Armadale in an industrial park sort of thing from memory. I got a little lost on my way but it's pretty easy to find. 

Yep, completely agree. Get the thermostat replaced. The needle on the gauge should be almost horizontal after 15mins of driving (Full temp), otherwise the thermostat is staying open. I would imagine this will also sort out the high idle issues. The temp sensor on the air box, well I don't think anyone has identified it as actually doing anything, you may be fine to run without out, check this after the thermostat is resolved.
 
Regarding the coolant system. It takes a bit of time to bleed properly. If you go to someone without any experience, at least get a copy of the BGB and provide this to them. It goes over exactly how to bleed they system correctly. Otherwise they'll do it all wrong and you could possibly cook the engine.

Hi All,
Thanks a lot for your comments & assistance.
I was looking at posts concerning draining & re-filling the cooling system, & was aware that there were challenges.
I was going to do it myself on the weekend. Has got green coolant in it, so will get some Nulon that other posts recommend.
In one of the cooling system posts, there is mention of a procedure or sequence for draining & re-filling that appears to include measuring the quantity of stuff removed & re-filling with a similar amount. I have downloaded a copy of BGB which shows locations of drain & bleed points. Can anyone provide a copy of a procedure, which should be followed. My thought is that draining is to open all vents, red cap, etc, before opening drain point. Refilling should be the reverse, closing drain & checking vent points until coolant flows from the vents, leaving highest, probably at the heater until last. I reckon that I probably need to flush out green stuff, but don't really want to put Perth water into it at all. May think about doing a preliminary fill with distilled water, & then drop it again. Question is, how difficult is the fill procedure, is it just slow & painstaking, & PITA.
Thanks again.

I agree that the fast idle would not be caused by that sensor being missing.
BTW it should mount in the hole with a rubber grommet and it needs to be replaced.  You should find the connecting wire hanging there somewhere too.
 
The IAT sensor does have a function, especially for fuel economy.
Check out: http://www.freeengineinfo.com/air-temp-sensor.htm

Peter, I have just sent you a PM.

yes, the ecu uses the IAT sensor and the sensor in the manifold (MAT) to adjust fuel trim for better economy/power etc
atleast in the speed density  version of the turbo it does, id assume the n/a is similar
toyota wouldnt have put it there otherwise.
in regards to coolant use the toyota red coolant they are about the same price and is a genuine product.
 
cheers

+1 to using toyota red coolant (Standard, not long life)
 
To drain the system, open the radiator cap. Put heater to full ON, if its auto controlled put the keys to ign to ensure this happens. Take keys our of IGN. Open all the drain points on the car, this includes: bottom of front radiator, engine block plug near intake manifold side of block + 2 plugs in the stainless steel lines that run under the fuel tank. Once drained plug all of these again. Next, open the bleed taps on the top of the radiator and the heater system. Put Pre-mix of coolant (use your own mixing method with distilled water - 50/50??) into car via radiator cap. Have someone watch the bleed valves at the front of the car. When fluid starts to come out, wait until a solid stream of fluid comes from the tap, then close them both off one by one. When the system is full, start the car with the radiator cap off and continue to fill until the thermostat has cracked open and the system will not take any more. stop engine + put radiator cap back on, put remaining coolant in overflow bottle. 
 
Have fun. its also easier to bleed with 2 people around.