Idle problems

[filh]

No I didn't unplug the TPS , and will of course try .Neither did I Block the air pass wilth finger , and I 'll try to , but I checked the AAV in boiling water and the valve opend . And the two small hoses are hot .

I did bleed the system several times , and with heater open .
I didn't change the AFR , but I can change it , but it's the same as former engine .
Could the oxygen resistor be fautly? As I think , by letting the engine running at that bouncing idle, it's a high pollution level . It's irritating in the eyes,when walking at back exhaust!

I will try all the solutions , but I tried so many that I 'm lost . Hope It won't have any influence on my next rally ride
thanks for your patience and suggestions
Phil

[jondee86]

Filh, while the exact cause of the problem is far from clear, there is one
solution that seems to work. If you can lower/stabilise the idle by
blocking the air bypass opening on a warm engine, then de-activate the
thermostatic idle-up valve.

The easiest way to do this is either (1) pull the valve off the throttle body
and make a blank gasket from some suitable waterproof gasket
material. Use this to replace the standard paper gasket. With no hole for
air to pass thru, the valve is blocked. Easy and reversible.

Alternatively (2) remove the thermostatic valve completely, and replace
it with an aluminium blanking plate. In this case you can remove or loop
the water heating hoses, and gain the benefit of a cooler throttle body

Cheers... jondee86

[filh]

Thanks Jondee , Did your first solution: made a blank aluminium gasket, and also removed the 2 small hoses ( made a loop) .
What I found is so strange : removing and retesting the AAV , fully working !
Problem is from one of the two small hoses leading to AAV .
The one connect to the solid pipe aside block is hot water full !
But the one coming from the rear of water pump is empty !
And the last fault I found???
I tested the Thermostat ,in boiling water , with no move .....
Had a try with two other , and got no reaction .
I heated the back of thermostat with a direct flame , and got it open !!!!
I guess I'm near the fault! Order a new thermostat and will test it in boiling water!


With the blank gasket under AAV , idle is smooth and stable .

Many thanks for your help , very useful
Regards
Phil

[jondee86]

Interesting If no hot water is getting to the valve, your idle is going
to stay high. High idle and a closed idle switch in the TPS means you
get this...

- engine speed goes high with closed throttle
- ECU says car is decelerating, and initiates fuel cut
- engine speed drops until ECU turns injectors back on
- engine speed goes high with closed throttle
- ECU says... bla... bla... and over and over again

Pulling the MAP sensor tube takes away one of the three required
elements for fuel cut to occur... there must be high vacuum. Likewise,
disconnecting the TPS takes away the closed throttle signal. Blocking
the air bypass port with your finger takes away the high idle... simple !!!!

So there you are... you have contributed to solving a mystery that has
had me wondering for a long time. Clear the blockage from that water
tube and you should be able to put your AAV back in place, and it will
work fine.

Cheers and good luck... jondee86

[Snejk]

My mechanic had to open the whole AAV case, then drill two holes in the round plate in order to turn it and re-calibrate the idle. Then he filled those holes with liquid metal or something and that was it. But the idle wasnt looping, it was either normal or too high. Now its as it should be.

[filh]

To Jondee , that's a good analysis . I think you have great electronic knowledge , and for sure about 4age managment!
Just can't find the reason why water is missing in the small, hoses. And I must add that there is no water in the hose connected directly on water pump . The one connected to solid metal hose along the engine block is coolant full!

I had no time to look further and ended my first rally this year !
I do think thermostat could be the cause , but my T° is ok , and i had no water consumption .

Thanks for all the helpers. Have another problem now , but will open a new post for it!!!!
Phil

[alimonos]

just throw air with high presure in one of the two small hoses and it will unblock them :wink:

[filh]

I of course did that , with no result . I dont think Hoses are cloggeg , coolant isn't passing from thermostat or water pump to that hoses !
Filh

[shawnho]

Thanks for all the tips. I've been having the same bouncing idle issue for a couple of years, but only when the ambient temperature is below 40°F (4°C) or so. I've been able to fix it in the past by cleaning out the vacuum side of the AAV with carb cleaner, but this winter it didn't help.

I tried your troubleshooting methods, but was unable to to block the port to the AAV just ahead of the throttle butterfly valve with my finger. If I remove the air intake between my air filter and the TPS to access the port, the car will not run. Do I need to disconnect the AFM at the air filter?

Anyway, when I took the AAV apart I found some RTV liquid gasket from a water pump replacement wedged into the AAV coolant inlet. The line from the engine was getting hot, so it must not have been completely plugged but I hope I solved the problem.

1985 Corolla GT-S AE86 - My wife's car when we met 19 years ago.

[jondee86]

shawnho Wrote:I tried your troubleshooting methods, but was unable to to block the port
to the AAV just ahead of the throttle butterfly valve with my finger.
If I remove the air intake between my air filter and the TPS to access
the port, the car will not run. Do I need to disconnect the AFM at the air
filter?

It is a bit more difficult with an AFM engine. When you disconnect the
ducting, you need to hold the AFM flapper open a bit (about as far open
as it is when idling). Otherwise the fuel pump switch inside the AFM goes
open circuit and cuts off the fuel supply (safety feature when engine stalls).

Cheers... jondee86