Q: Stalling at low speeds and idle.

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I recently had autozone run the computer on my truck and it came back as failing cat and ignition coil. I eliminated the cat and replaced the ignition coil. The truck runs much better, but i hit that same issue with the killing. again, it runs better, but the killing hasnt stopped. should i replace the wire from the ignition coil to the distributor cap? i did a full tune up about 3 years ago so all the wires and spark plugs were replaced. i dont remember if i replaced the distributor cap or not. i think i have it narrowed down to either the wire from the ignition coil to the distributor cap, or the distributor cap. thats my guess. the way it kills is at an idol or at take off. now that i replaced the ignition coil and cut the cat off it starts back up much easier (before it would have to sit for hours). suggestions?

My car has 220000 miles.
My car has an automatic transmission.

I would recommend checking the idle air control valve to see if it is dirty or working properly. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. This is also an important function when starting the motor as it allows the motor to run and idle on it’s own once the motor fires. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed while adjusting the air/fuel ratio constantly to allow this to happen smoothly. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle. You can test the functionality of the valve by checking its electrical resistance if you have access to an ohm meter. To do this, disconnect the IAC valve, connect an ohmmeter to pins 2 and 3 of the valve. If you get a resistance value between 10-14 ohms, it indicates IAC valve is working as it should. Next, connect the ohmmeter to pins 1 and 2. If you do not get a resistance value between 10-14 ohms, the IAC valve may need to be replaced.

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