AE100 5A-FE cold idle problem

pavithra.kulasekara (Pavithra) 2020-01-01 07:19:40 +0500 #1

Hi
Corolla AE100 5A-FE engine. 246000Km Odometer.
when cold start (around 27 degrees C) car start fine and idle around 900-1000rpm. if I turn on AC, engine suddenly become slow and AC clutch disengage to prevent engine stall. sometimes engine stall. when I drive, car feel lack of power.

this car idle 800-900rpm when warm. turning on ac, slight increase rpm and runs fine. no idle drop.

this happen only when engine cold.
I checked coolant temp sensor, IAC valve, throttle body, TPS. all within specs. what could be the problem? low compression?

I heard this engine should run 1300-1400 rpm as soon as cold start. but mine never run at this speed when cold.

omersiddiqui5482 (omersiddiqui5482) 2020-01-01 09:06:59 +0500 #2

Your Car most probably has a Vacuum Leak

pavithra.kulasekara (Pavithra) 2020-01-01 10:39:02 +0500 #3

Thanks for response. there is no noticeable leak. resealed throttle body with sealant, I checked to close vacuum hoses. but no difference.

Anyway, If it have a vacuum leak, engine should idle faster.. isn't it? in my case engine cold idle around 1000rpm.

anon36782927 2020-01-01 10:45:43 +0500 #4

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pavithra.kulasekara (Pavithra) 2020-01-01 11:11:08 +0500 #5

IACV is working. I tested it and following ways:
connect +12V to middle pin of IACV, connect other pin to ground close the valve (engine stall) and other one open the valve (rpm increase) and warm engine, disconnect IACV connector -> rpm increase. so valve is functioning, receive signals from ECU.
But when Engine cold, (+28C) should IACV open more than 50% ? in my case, upon a cold start, disconnect IACV connector not change rpm.

IACV stay at 50% middle position when disconnect. it adjust and close by steps as engine warms up. does anyone know when it open more than 50% ? at what temperature?

AC idle up VSV is working. disconnecting it immediately stall engine (cold engine, AC on)

anon36782927 2020-01-01 11:23:27 +0500 #6

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pavithra.kulasekara (Pavithra) 2020-01-01 11:31:22 +0500 #7

Currently I do same method.
Anyway, I want to know cause for this
I suspect that engine has low compression when cold. because this AC problem and I feel lack of power.

pavithra.kulasekara (Pavithra) 2020-01-01 11:32:07 +0500 #8

There was no thermostat when I buy the car. I installed new one.

anon36782927 2020-01-01 11:35:25 +0500 #9

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omersiddiqui5482 (omersiddiqui5482) 2020-01-01 11:37:56 +0500 #10

Observe one thing! when you start the car cold the RPM should be higher than usual the ECU does that to attain operating temp quickly is your car doing this?

pavithra.kulasekara (Pavithra) 2020-01-01 12:29:43 +0500 #11

10w30 oil

pavithra.kulasekara (Pavithra) 2020-01-01 12:31:35 +0500 #12

cold start rpm is around 1000rpm. after engine warm up, it reduce to 850-900rpm. But I think, cold start rpm should be higher than 1000. I saw another same car same engine cold start rpm goes 1300 - 1400

omersiddiqui5482 (omersiddiqui5482) 2020-01-01 12:34:40 +0500 #13

usually my efi car has RPM between 1200-1300 idle at cold start and then it settles down to 1000 as the car reaches operational temp!
Sir it is rather better to get the car scanned and check if any error is captured by the system!

pavithra.kulasekara (Pavithra) 2020-01-01 12:40:19 +0500 #14

This car have no OBD2 port. so I connect TE1 E1 to see blink codes. no error codes. check engine light continue blink
I will show the car to a mechanic as soon as possible

omersiddiqui5482 (omersiddiqui5482) 2020-01-01 12:45:52 +0500 #15

@dani_kk sir what do you suggest!

Hassan1991 (Electrical Engineer ) 2020-01-01 14:16:46 +0500 #16

Your car iac need setting. 5afe has VSV located on firewall for ac it is also adjustable (usually) , rpm should be 1200 on cold start.

pavithra.kulasekara (Pavithra) 2020-01-01 15:21:12 +0500 #17

How to setting / adjust IAC?

Hassan1991 (Electrical Engineer ) 2020-01-01 19:12:42 +0500 #18

First clean it.
Then, If you check the bolts on which iac is connected to throttle body, they have adjustment.
You can also set the idle speed screw as required.
The lack you power you feel in cold can be due to oil, at it gets thick in cold weather.
Ecu riches the mixture to over come loose of combustion going on in cold condition but there will still be difference between power.

pavithra.kulasekara (Pavithra) 2020-01-01 19:42:04 +0500 #19

there are two bolts that IAC coil connect to valve pintle. if I loosen them, there is a slight space to rotate very little. I keep coil centred and fasten bolts. will try to adjust it.
Valve inside cleaned.
once I turned idle adjustment screw (adjust throttle plate opening) to slightly higher rpm. but then warm engine idle also increased to 1200rpm.

Hassan1991 (Electrical Engineer ) 2020-01-01 19:59:59 +0500 #20

Yes.
Adjust that screw again when car is warm.