Idle speed problem

[getnhi1]

My car doesn't like to idle down, I can snap the throttle and it comes down. Before anyone says check the throttle cable I did, its got slack, it hits the idle switch, but doesn't idle down, it has to hit it hard, I can snap the pedal or snap the throttle valve under the hood and it comes down. Before i mess with the idle switch I wanted to find out about it, I noticed its adjustable, I think maybe it just needs adjusting, is there a procedure for that?

[mechanicaldj]

may need to clean the throttle body out

[ericsmith32]

remove and clean the iac also, it's on the drivers side of the intake manifold.

[getnhi1]

Throttle body was cleaned recently. I can get it to idle down, I just have to snap it, it idles down everytime if I do that. I'll see about the IAC, I only have a Haynes so I'm limited to info on this car.

[ericsmith32]

I wonder if you need to check the tps, it could be weak also. That should be easy to check with a multimeter.

[getnhi1]

I wonder if you need to check the tps, it could be weak also. That should be easy to check with a multimeter.

Yea that too, didn't even occur to me. Whats a multimeter? Just kidding. :lol:

[getnhi1]

I noticed today, if I turn the car off and restart it, without touching the gas it will idle down. Checking the TPS now.
TPS and idle switch are fine. Seems to point to the ISC-BPA, the resistance on it is ok, that as far as the haynes takes it.

[getnhi1]

Question, what does the ISC-BPA control, besides the fast cold idle. Since there is an idle speed screw on the TB, what does the ISC actually do.
Now my idle won't come down at all, nothing I can do makes it idle down anymore.

[getnhi1]

I fixed it! I think, someone has jacked with the &*%#@ idle screw, :x the air snorkle had a leak, its since been sealed, and I've been running FI cleaner through it, both of these things caused the idle to increase, the idle screw was already open to far, thus the ISC lost control.
The ISC must be a duty cycled solenoid I'm guessing, reading the voltage to it on a meter, (meters read average voltage) the higher the voltage the more open the ISC is, I turned the idle screw in until the voltage started going up, that is the point the ISC gained control, once at this point it didn't matter where the screw was, turn it in more and the ISC voltage goes up to compensate, idle stays constant, I left it at 2.7 volts, it may be off a little but at least its working for now.
According to Haynes you put it in base timing mode and set the idle speed screw there, I just need to find the dist reference wire for my tach and this problem is done.
Anyone happen to know which wire?