I am having surging all the time but bad at idle. When I start the car there is a loud sucking noise comming from the TBI right above the IAC if I put my finger over the hole I can cut down on the sucking and the car will idle better. If the sucking goes way the car idles great, nice and smooth around 550 when the it starts sucking again it surges from 1200 to 600 rpms and sometimes stalls. I put a new IAC in and it still does it. What controls the IAC and why would it work and then not work?

I have replace fuel pump, filter, map, IAC, distributor, temp sensor, wires,plugs, O2, rebuilt TBI and exhaust but nothing has changed.

 

I'm assuming you did the IAC reset procedure when you replaced it correct?

 

If you mean than yes and it is ok until you restart the engine and it goes back to sucking and surging.



Reset the IAC valve pintle position by performing the following.

- Depress the accelerator pedal slightly.

- Start the engine and run for 5 seconds.

- Turn the ignition switch to the OFF position for 10 seconds.

- Restart the engine and check for proper idle operation.

That's it.
Also if you mess with the idle control screw than I believe you must adjust the TPS .(Throttle Position Sensor) maybe someone can verify that.

 

this is the procedure i always use if i mess with the IAC

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