Starts but will not stay running, IAC reprogram?

ANGELA BYRD

MEMBER
1992 CHEVROLET SILVERADO
V8
AUTOMATIC
200,000 MILES

The truck listed above is a CK 1500. I previously read in a post that if you disconnected the battery or replace the battery that sometimes the IAC may need to be reset. The post gave the answer as if you would have the scan tool. I do not have a OBD1 scan tool. I can check the codes with a paperclip, however how do you reset it so that the IAC can go back to its defaults?

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,716 POSTS

Hi,

On this vehicle, the IAC shouldn't need reset after battery replacement. Can you let me know what is happening? For example, are you able to keep the engine running if you press lightly on the throttle pedal or does it stall regardless?

Also, could you check for codes? I'm curious if you have a code 33 or 34. Also, I need to know what size V8 engine is in the truck.

One other thing. Take a look at this link. If you are able to keep the engine running, this may be very helpful for this problem.

https://www.2carpros.com/articles/engine-stalls-idles-too-high-low-after-dead-or-replaced-battery

Let me know.

Take care,

Joe

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Thursday, January 5th, 2023 AT 3:55 PM

ANGELA BYRD

MEMBER
3 POSTS

Engine is 350.
Not too long ago I was able to keep the truck running if you keep your foot on the gas.
Now, it stalls every time you crank it after a few seconds. Sometimes if I give it gas after it starts, I'm able to keep it going longer. When you take your foot off gas it cuts off.

The code it gives us #15 coolant sensor.

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Thursday, January 5th, 2023 AT 5:00 PM

JACOBANDNICKOLAS

MECHANIC
109,716 POSTS

I think you found the issue yourself. The ECT code is likely your answer. The coolant temperature sensor is used by the ECM. With the signal from the ECT sensor, the ECM controls the idle air controls, fuel delivery, EGR, and so on. I feel that is what you need to check first,

Just for curiosity, what is the temperature where you are located? Do you notice any smoke from the exhaust when it runs? Based on the code, I suspect the coolant temp sensor is indicating the coolant is 40 degrees below 0. As a result, the computer is dumping fuel to the engine thinking it is required for the engine to run under those temps. Instead of helping to run, it is causing the engine to get too much fuel and flood.

Now, there are two coolant temperature sensors on the engine. One is for the ECM and the other is for the fan/temp gauge. The one you need to replace is on the top of the engine, not the one on the side. I attached a pic below.

Replace that and let me know the results. Keep in mind, if I am correct, the engine may run rough for some time from being flooded.

It's a theory, but I feel this is the issue.

Take care and let me know what you find.

Joe

See pic below.

Image (Click to make bigger)

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Thursday, January 5th, 2023 AT 8:53 PM

ANGELA BYRD

MEMBER
3 POSTS

Okay, so the coolant sensor has been replaced and code is gone. Truck starts runs smoothly after self-adjustment and shuts off after 3 seconds. Can't figure it out.

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Wednesday, January 25th, 2023 AT 3:00 AM

JACOBANDNICKOLAS

MECHANIC
109,716 POSTS

Angela,

Does it sound like it is running out of fuel and slowly stalling or does it seem more like the ignition key is being turned off?

Also, let me know what size V8 engine is in the vehicle.

Take care,

Joe