Once more into the void - 5ktq high 'idle' - update

E. Roy Wendell IV erwendell at mac.com
Fri Oct 27 12:23:35 EDT 2006

> as suggested by Ben, I pulled the isv connector with the car
> running and the idle dropped - a bit low but very acceptable.

That means that the ISV is good. Disconnected it closed under spring  
pressure and shut off the idle air circuit except for the passage  
through the idle bypass screw on the top of the throttle body. You  
now have a car without electronic idle control.

> plugged it back in and nochange in idle

This is because disconnecting the ISV causes the idle controller to  
shut down. I don't know whether it's a driver protection feature or  
what but in any case the controller becomes inactive once it senses  
an open in the ISV circuit.

> , went for a drive and the problem was gone - it came
> off high
> speed, down to a low idle at all times.

Same as above. You are in mechanical fixed idle mode.

> got home, shut off, restarted and zoom - 3k rpm with no throttle....

Because the controller reset when you cycled the ignition power.

Now it's back to checking the controller inputs and the controller  
itself. I'm leaning toward an input signal problem because the idle  
controller is not only sending the wrong signal to the ISV it's also  
failing to trigger the backup idle limit by way of the deceleration  
valve. It this were simply an air leak problem via either the ISV or  
bad plumbing then the idle controller would be opening the decel  
valve which allows intake air to bypass the air flow plate and cut  
the fuel long before the engine speed could reach 3000 rpm. For some  
reason the idle controller thinks that 3000 rpm is ok and that would  
only be the case if it thought the throttle was at other than idle.

Roy Wendell
erwendell at mac.com
Too many type 44 tq
A pair of MR2s

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