High rev problem
06-29-2013, 07:41 PM
Post: #1
High rev problem
I have a recent serious problem that i need your help if somebody can help me.

Some time ago i wanted to find a cable that i can cut it off with a switch so that my ae86 wont start.
As i was searching near the ecu i found one with black color and a continuous red line running along the cable with red circles also with about 2 cm space between them. I cut it, inserted a switch and the car didnt fire up. With all this mess of cables i could not find what it was, except that it was going at this yellow plug that you can see in the pic.
The switch worked perfectly with only one remark. When sometimes i forgot that i had the switch off and tried to fire up the car it made a sound like a relay trying charge repeatedly and only when i turned the keys to ON position it stopped.
Of course when that happened i immediately turned the key to ON position so that i wont create any problem.

What happened 2 days ago is that i parked at my house and i turned the switch off before the keys of the car. So the engine started to go off and after a second, before i could turn the keys off, i started reving high at about 2000 rpm. Immediately i turned of the keys.
After that and until now when i start the car it revs immediately at 2000 rpm all the time my ae86 runs. No matter cold or warm engine.
And also the switch isn't working anymore. On or off its just the same, like it doesn't exist.

Anybody familiar with any solution?
[Image: AEU86 AE86 - High rev problem]
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07-01-2013, 02:19 AM
Post: #2
High rev problem
Impossible to say what has happened without knowing where those
two B-R wires go ? From memory, most of the blue wires are for things
like the wipers and washer, and one of the B-R wires should be a power
supply from near the underhood fuse box.

I don't even know how/why your idle should go high ? Usually it takes
extra air into the intake manifold to push the idle up ? Whatever, I would
get that switch out of there, as you don't know what it is interfering with.
If you want to install a cutoff, most alarm systems install a relay in the
power supply to the coil/igniter.

Then try and find out what is pushing the idle up, and work backwards
from there. Check every fuse you can find, every relay, see if the
engine check light is showing any fault codes, and maybe see if you
can find a spare ECU for testing. Good luck !!

Cheers... jondee86
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07-01-2013, 03:10 AM
Post: #3
High rev problem
Were does the black red wire go to? Engine loom? If its the plug I'm thinking of, the blue ones are washer and wiper and the 2 blk/rd the power to injectors, etc, they are allways black/red ord black orange on any toyota I´ve done some wiring on...

On a guess, if youre lucky you broke the switch, but you might have killed some of your electrical components, as you can see its a big wire, that can withdraw something like 18amps, switching that under load is a bad idea, cause you get a good spark and a nice peak on the voltage, wich can break ecus and ignitors.

Don´t really understand how it whould raise the idle but, thats up to what you broke
Banging head

1979 Toyota Corolla KE35
1983 Toyota Corolla AE86
1985 Toyota Corolla AE86
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07-02-2013, 07:30 PM
Post: #4
High rev problem
Looked it up on the wiring diagram you cut output of the main EFI relay, which does ignitor, dizzy, coil, an a few other thing. what a stupid thing to do!

1979 Toyota Corolla KE35
1983 Toyota Corolla AE86
1985 Toyota Corolla AE86
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07-02-2013, 09:44 PM
Post: #5
High rev problem
Problem found and solved.
First of all i found out that this wire goes to the circuit open relay as shown in the pic. Luckily i didnt destroy it.
[Image: AEU86 AE86 - High rev problem]

But first things first. I've installed a 20v blacktop to my ae86. I've removed the plenum and use itb's. So the idle tube of the idle control valve is tapped with a screw.

Now with a 100% rare coincidence when i turned off the switch of the cable i told you, that screw might have been loose and with the engine vibration when it was dying it fell to the floor. Almost immediately when i turned off the switch. So the idle tube sucked air freely and caused the high rpm.
The fact now that these two events happened at the same time made me think that the high rpm was because i turned off the switch under load.

Anyway i found the screw and put it back in the idle tube more secured this time. And the problem was fixed.

There is only one mysterious thing to be solved now to my curiosity, because i dont now about electrical circuits.

With the screw in the idle tube, and if i have the switch at the OFF position(as if for example the black wire would be cut), the engine wont start. If i turn the switch ON it starts normally.
Now when the idle tube is not tapped( these were the last two days until i solve the problem) the engine fires up even if the switch is OFF(as if the wire was cut permanently), immediately at 2000rpm as i told you before.

Now can anybody more familiar explain me this weird thing?
What could possibly be the connection between the relay, the idle control valve and the idle tube being tapped or not!!!
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07-03-2013, 12:05 AM
Post: #6
High rev problem
I am puzzled also Tongue On a 20V engine, all of the idle air usually goes
thru the ISCV. If you block the ISCV hose, the engine will either stall, or
struggle to keep running at 400-500 rpm. So I wonder what hose you
have blocked, and how the engine can idle without air ?? Did you adjust
the throttle arm stop screw to keep the throttles slightly open ?

Cheers... jondee86
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