MR2 Newbie Questions

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.

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.
 

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.

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

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

DONT MIX THE COOLANTS.
 
mixed coolants can solidify and clog pipes and channels....
 
also make sure you read the instructions on bleeding and flushing the system... no shortcuts.

Hi All,
Thanks for all of the responses & information.
Have done the job, replaced the Thermostat. Old Thermostat had movement just flopping around loose.
Internals all looked nice & clean.
Filled & flushed with distilled water twice to remove as much green coolant as possible.
Followed the procedure. Had no real difficulty, just a little awkward doing it on stands in the garage.
Idling o.k. now. Will keep a close eye on coolant level for the next week or so.
Thanks again.