Idle problems

[filh]

AAV removed , I tested it in hot water , and it's working . Also made a test with two other valve , and they work same way ! So I can say the AAV is ok .

Checked the two small hose leading to AAV , but they are clean, and were full of coolant . (So did the heater hose too)

Tried to bleed the cooling circuit : radiator cap open, heater open , warming till gauge is in midle of range .
But No result again , the idle is bouncing . The only way I can stop that is too disconnect the Vaacum sensor hose from collector . The idle is than
stabilised .

Getting nervous ......

[Sanity Clause]

Did the 2 hoses leading to the AAV get hot, enabling the valve to close?

I would try a diagnostic next, to see if that throws up any codes. Maybe the TPS needs adjusting?

[filh]

Yes they are both hot and the AAV is fully working .
For the engine code ;
I got 8 blinks , which means : intake air temp sensor signal.
I of course changed that sensor , whitout any results.
TPS : I don't like to adjust it , it's so difficult . And why would that sensor be faulty , as I changed the engine only , all periphericals are same as former engine ?
thanks for trying solutions
Phil

[jondee86]

I have been interested in this "loping idle" phenomenon for some time,
and have yet to figure the true answer.

Basically, although cleaning or replacing the thermostatic cold start idle
up valve appears to help a lot of people, it is only part of the cause.
There is no way the capsule can expand and contract fast enough to be
the whole cause.

The true cause appears to be a combination of fuel cut switching, ECU
sub-idle "anti-stall" response, and MAP sensor reading. The fact that
you can stabilise your idle by disconnecting the MAP sensor tends to
confirm its involvement.

Have you checked for a major vacuum leak, such as a missing nose
insulator on one of your injectors ??

Cheers... jondee86

[parrot]

If you don't bleed the cooling system well, you get an airlock at the back of the head. Sitting back there is the ECU coolant temp sensor. If you have an airlock you will get the idle situation you describe. It has happened to me and my highly experienced Toyota mechanic mate tells me it is common. Bleeding can be very fiddly.

Might be obvious, but check also you plug the loom plug back onto the sensor. Can't remember offhand if it is the green or brown one.

[Sanity Clause]

8 blinks....

Could simply be a loose connection at the air thermo sensor.

Worth checking this area first anyway.

[filh]

TO Jondee : I tried to change injectors, whitout result.No leak found on vaacum system , but problem must be near that . changed twice the vaacum sensor : no result . But each time I disconect the hose from that sensor , idle get quiet.....


To Sanity Clause : also changed the intake air temp sensor , no difference .
I also tried to disconnect it when the engine was running ,whitout result !

To Parrot ; I bleed I bleed trying several way to do it , whitout success.
I remove the water temp sensor at the back of head , and I can see coolant .
I slightly loose hoses , but only got coolant from them!

Ghosts are among ae86 world......


phil

[parrot]

If your sensors and all other peripherals were working before you changed the engine, they will still be working now, as long as everything is plugged in which it sounds likely to be.

The only thing changed by the sounds of it is the cooling system obviously. Do you still have a heater connected? Was it open to heat when you bled it? Keep trying, make sure you squeeze all the hoses once the thermostat opens so there are no bubbles etc.

If nothing else was changed between engines, I cant see what else it would be. The cycling idle, up to 2500 rpm and back to normal and over and over is exactly what you see with coolant sensor problems.

Good luck.

[jondee86]

If you unplug the TPS, does the idle stabilise ??

Did you try blocking the air bypass hole in front of the throttle plate
(RHS about 4 o'clock) with your finger while the engine is running ??

Is the throttle plate all the way closed when idling ??

Cheers... jondee86

[JonnyAE86]

I had a similar problem in the past, my daily driver idled ok but when i did a major highway run when i got in neutral/clutch the rpm was like 3500 sometimes 5000

I ALSO thought it was a water clogs in tb or some vacuum line disconected, checked it for days, i even switched ECUs and all that...

Truth is i changed the fuel pressure regulator and it never happened again. I dont know if this is the case but try testing with another one just in case.

Hope it helps