2000 corolla

[Natedawg]

hi 2000 corolla.. made in canada. code p0505.. two trip DTC... well car has an idle of 1800 rpm.. only time it reads normal is when the car is in gear such as reverse and drive.. i swapped known good parts.. MAF, THROTTLE BODY, IAC VALVE, FEW ECM THAT WAS FOUND AT JUNYARD STILL NOTHING.. if i unplug the IAC VALVE, IDLE IS STILL HIGH..i dont know what to do im really stuck.. i have power and ground. so i dont know what it could be.. dont think its a vacuum leak.. i sprayed carb cleaner..

[visch1]

I'm almost positive it has to do with the computer control. My manual transmission won't go below about 1400 to about 700RPM until it's water temp is around 180 degrees. Perhaps your thermo is not the right one.

[Natedawg]

Originally Posted by visch1

I'm almost positive it has to do with the computer control. My manual transmission won't go below about 1400 to about 700RPM until it's water temp is around 180 degrees. Perhaps your thermo is not the right one.

your saying the thermostat is bad??? it blows warm air with no problem when warmed up???

[Highway_maniac]

Originally Posted by visch1

I'm almost positive it has to do with the computer control. My manual transmission won't go below about 1400 to about 700RPM until it's water temp is around 180 degrees. Perhaps your thermo is not the right one.

Don't think it's the thermostat. When an engine is cold, the idle will be higher (or the engine will stall). 1400 cold sounds about right, 700 when the engine is hot is dead on.

There is a small valve (IAC valve) on the throttle body that regulates this higher idle speed, it opens up more when cold, allowing more air to the engine. The ECU (that also regulates the valve) orders the injectors to inject more fuel. Result - engine rpm go up. If this would not happen, your engine will stall.

Topic starter mentions that the blower blows hot air, thus I don't think that will be the problem. He also mentions that the problem only goes away when the car is in gear (drive/reverse), he does not mention that the problem goes away when the car is hot.

I don't have a automatic transmission, and don't know how this is linked up with the throttle or ECU so can't help the topic starter. First thing i would do if this happens to a car, is to disconnect the battery for a few minutes. This resets the ECU, whereafter it has to relearn itself. If you have electrical stuff you don't want to disconnect (radio with presets ect.) pull the ECU fuse, replace after few minutes, same effect.

[Natedawg]

Originally Posted by Highway_maniac

Don't think it's the thermostat. When an engine is cold, the idle will be higher (or the engine will stall). 1400 cold sounds about right, 700 when the engine is hot is dead on.

There is a small valve (IAC valve) on the throttle body that regulates this higher idle speed, it opens up more when cold, allowing more air to the engine. The ECU (that also regulates the valve) orders the injectors to inject more fuel. Result - engine rpm go up. If this would not happen, your engine will stall.

Topic starter mentions that the blower blows hot air, thus I don't think that will be the problem. He also mentions that the problem only goes away when the car is in gear (drive/reverse), he does not mention that the problem goes away when the car is hot.

I don't have a automatic transmission, and don't know how this is linked up with the throttle or ECU so can't help the topic starter. First thing i would do if this happens to a car, is to disconnect the battery for a few minutes. This resets the ECU, whereafter it has to relearn itself. If you have electrical stuff you don't want to disconnect (radio with presets ect.) pull the ECU fuse, replace after few minutes, same effect.

yes im clueless.

[leakyseals]

I would suspect an intake manifold gasket, throttle body gasket, some leak along the intake. Try spraying around the intake and TB with TB cleaner, see if you can stall it.

[visch1]

"your saying the thermostat is bad???"
No but it's possible, and might be the wrong one for the engine.

"it blows warm air with no problem when warmed up???"

I think the correct thermostat is set for 180-200 degrees which is much higher than the warm quoted. At idle the radiator fans on my '98 come on at 200. This is measured with a Scan Gauge, not by feel.