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2003 Chevy truck, low idle

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IHateMyJob2004

IHateMyJob2004

Lifer
I have reason to believe that some old gas (last summers lawnmower gas) I tossed in my tank may be a contributing factor, but the timing here is odd.

I had a dead battery, so I replaced it. That's when I noticed that my idle was way to low. At around 400 rpms. Is there anything that changing a battery could have done to my truck to cause the idle to drop?

The idle is computer controlled correct?

 
Your truck is ok.

I have 2004 with the 5.3 and when the ECU loses memory it does this too.

This truck should be drive by wire. Everything is electronically controlled and relearning what RPM it needs to idle at.
 
Found this elsewhere (I haven't checked my voltage setting)

Question:
"I have a 2003 chevy silverado with the 4.8L v8. The motor dies while moving at idle speeds mostly while making a turn. I noticed while sitting in park the voltage meter drops and the engine pulls way down."

Reply:
"There is a service bulletin for that problem on your vehicle. It involves two things. A software update for the engine controller and a cleaning of the throttle body."

Bulletin No.: 04-06-04-040
Date: June 14, 2004
Subject:
Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body)
 
Originally posted by: IHateMyJob2004
Does anyone know if my truck has a low idle set screw on the throttle body?
Click to expand...
Those haven't existed for decades. Some GM cars used to require a procedure to relearn the idle control after a battery disconnect. I would think yours is too new for that.

Drive it for a while and see if it corrects itself. If not, you may have to take it in. I don't feel that information you found is relevant to your situation.

Wish I could help more.

 
My '91 Eclipse did the same thing. It used to eat batteries and had this problem with a new battery. It would correct itself after a day or so of driving.
 
My 2004 Silverado does the same thing everytime I reprogram it with my Hypertech Power Programmer... (in effect, the same as disconnecting the battery as it clears the computer) it just has to relearn it's correct idle speed. I drive mine around for around 15 minutes after programming and it fixes it all up.

Just make sure to keep your foot near the gas because it will die if you let the idle go low enough.

Jugs
 
As some predicted, things are actually getting better. My truck is now idling at just over 500 rpm. No more worry of stalling but it still strugles on occasion. Maybe 600 rpm is the target.

The only thing that sucked thus far is when I was turning in a parking lot today and my truck stalled. I just started turning so the angle I was taking wasn't so hot. And you all know what braking is like when you have power breaks and no engine running. I was lucky to not hit anyone.
 
Umm, I'm thinking maybe you do have a problem. Although my opinion (supported by others too) is that the idle speed needs to be re-learned, the system should still be capable of maintaining an idle speed.

There is an IAC (Idle Air Control) solenoid that moves a plunger that controls the idle speed. It's controlled by the computer. The passage through which the air flows may be partially plugged with carbon.

It seems like quite the coincidence that old gas, new battery and a carboned up throttle body all converged at the same time, but stranger things have happened.

When you are now saying that the truck is stalling at low speeds in turns (like the information you found) I now start getting concerned. It's become more than an annoyance, I consider it a safety issue.

If it was mine, I'd remove and clean the throttle body. If that's not something you want to tackle, take it in. If I were you I'd start there and do the software update as the next step.

BTW, I add old lawn mower gas to our cars from time to time. Sometimes as much as 5 gallons. Not real old though. I mean it still smells like gasoline. 🙂

 
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