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03 Silverado-- L0w Idle & Stalling


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#16 az'03Silverado

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Posted 15 October 2007 - 06:47 PM

GMTRUCKTECH that sounds like the ticket.
Silver03ado: Is there any noise coming from the AC compressor or from the alternator? If one of these is seizing up it could give the symptoms. The dead battery is what makes me say this. If the alternator is about to take a crap, it may be hard to turn and may not be puting out the proper amps.
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#17 White Boots

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Posted 15 October 2007 - 07:51 PM

Listen to me I hvae been fixing these trucks with this idle stumble and a/c inop since the electronic throttle body came out on the trucks. The throttle body actuator is binding up and causing the unstable idle. I have tried cleanig them and so on with no luck. Replace the throttle body and gasket and take it to the dealer and have them update the pcm to also improve the idle stability. Do this and all your worries will be gone!


We see this a lot...CLEAN the throttle body and passages with a spray on t/body cleaner and toothbrush, then try it. If that doesn't work you MAY have to replace it, but cleaning it usually does it. We recommended this done every 20-30,000 miles. Also reflashing the PCM should be done, but that isn't the problem.
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#18 silver03ado

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Posted 15 October 2007 - 08:13 PM

AZ03SIlverado-
From what I see and the mechanic that took a look today as well as checked for codes....no abnormal or obvious bad sounds coming from the alternator or the a/c.

At idle speed, the a/c doesnt come on- idle is really low and the compressor doesnt engage. But at 10mph and up, once rpm is above 300-400, the a/c blows nice and cold.

GMTRUCKTECH: I appreciate your honesty. Could it hurt to try with the seafoam deep creep or should I try it to see if it works. What does a new TBody cost these days for my 03 5.3l silverado. Please advise.

WHITeboots: i take it that you also work on these trucks a lot...I would really like to do the cleaning on the throttle body, just havent found the place to properly inject the deep creep with the engine running. Looking for a pic of my engine bay 5.3l 2003 with markings of where to inject it....Disconnect entire intake? no? Disconnect MAF or not? etc...

ALSO- Reflashing the ECM...Is a dealer the only one who can do that, and what do they charge for it? My mechanic referred me to a computer place called ACE in Davie, FL "Auto Computer Exchange" on Stirling road...Are private companies able to do that reflashing as well.?
Thanks a ton

Edited by silver03ado, 15 October 2007 - 08:15 PM.


#19 Norseman

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Posted 15 October 2007 - 09:02 PM

WHITeboots: i take it that you also work on these trucks a lot...I would really like to do the cleaning on the throttle body, just havent found the place to properly inject the deep creep with the engine running. Looking for a pic of my engine bay 5.3l 2003 with markings of where to inject it....Disconnect entire intake? no? Disconnect MAF or not? etc...


Unplug the MAF sensor, then remove the intake tube from the TB.
Crank the truck (it should run maybe not real smooth but it will run) This might set a code just bring it to a part store to reset or let it reset on its own.
There is a small hole in the bottom of the throttle plate spray it in there.

You should still take the TB off the intake manifold, use a good TB cleaner and spray the hell out of the TB with the engine off and wipe it down.

Edited by Norseman, 15 October 2007 - 09:05 PM.

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#20 fourwheelinfool

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Posted 15 October 2007 - 09:49 PM

The first thing I do when there is an electrical problem is check for loose grounds... everywhere. Even a tiny little inconspicuous ring terminal will cause a low idle with stall. Sure she'll start fine and RUN fine but idle, watch out!



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#21 Krambo

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Posted 16 October 2007 - 08:34 AM

One more question, Did you install a lower temp thermostat? If you did, the PCM should be reflashed to drop your adaptive idle (learn) temperature in the range of the thermostat. Everytime you lose power to the PCM, the adaptive learn parameters reset.
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#22 silverad03

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Posted 16 October 2007 - 09:18 AM

Everyone has their own opinion and twist on what the problem might be and how to fix it, so here's my $.02:

A few weeks ago when it was really hot here my battery died. I got a jumpstart at work, drove home, and then couldn't get it started again. My factory battery was dead and gone when I had it tested at AutoZone.

After I put the new battery in, I had a couple days of very low rpm idle and stalling similar to your symptoms. When the weekend came around I took my truck out on the Interstate - I did a strong acceleration coming up the ramp and then cruised at 75 mph for 15 minutes. After that, the idle and stalling problems smoothed out and everything is back to normal now. I think the PCM just needed to re-adjust itself.

A lot of people here are throwing parts and money at the problem, and I think there are some card-carrying SeaFoam dealers in here (SeaFoam may be a good product, but reading in these forums you might be led to believe it will cure any and all automotive problems). I would at least give the truck an opportunity to fix itself before you invest money and time in cleaning the throttle body, etc. If the condition doesn't change after a good cruise, then I would make sure your battery cables are tight, your connections are clean, and you didn't disturb any grounds when you replaced the battery. There's a good chance it is a simple electric issue.

My $.02.

Edited by silverad03, 16 October 2007 - 09:21 AM.

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#23 GMTRUCKTECH

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Posted 17 October 2007 - 01:33 PM

Ok guys here is some proof of what I have been saying all along. I just got done fixing a 03 silverado with the same complaint by replaceing the throttle body and updating the pcm. You can try to clean it 1st if you want gm says use top engine cleaner but for me I have never had much luck with that. Here is the proof!






Posted Image Subject:Idle Instability, Low or Rough Idle with Electronic Throttle Control (Clean Throttle Body) #04-06-04-040 - (06/14/2004)




Models:2002-2003 Cadillac Escalade, Escalade EXT

2000-2003 Chevrolet Silverado, Suburban, Tahoe

2002-2003 Chevrolet Avalanche

2000-2003 GMC Sierra, Yukon, Yukon XL

2003 Hummer H2

with 4.8L, 5.3L or 6.0L V8 Engine (VINs V, T, Z, N, U - RPOs LR4, LM7, L59, LQ9, LQ4)

and Electronic Throttle Control





<A href="http://service.gm.co...m#ss1-1527156">
Condition
Some owners may comment on an idle instability, low idle speed or rough idle.

<A href="http://service.gm.co...m#ss2-1527156">
Cause
Condition may be caused by deposits in the throttle body bore.

<A href="http://service.gm.co...m#ss3-1527156">
Correction
Clean throttle body bore and throttle valve plate of carbon using a shop rag and an appropriate cleaner. Refer to Engine Controls Repair Procedures - Throttle Body Cleaning Procedure. This procedure may be performed at any mileage necessary. Check to determine if the PCM calibration has been previously updated to one that includes the update for throttle body coking. For 2003 model year vehicles, look in the operating system portion of the calibration. For 2000-2002 model year vehicles, look in the engine portion of the calibration. If not, then update the PCM calibration to the latest calibration. :ughdance:
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#24 Krambo

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Posted 17 October 2007 - 01:44 PM

...Also make sure you use Throttle Body Cleaner and not Carb and Choke cleaner. There is a difference and using Carb and Choke cleaner will strip the teflon coating off the throttle blade. It will flake right off. :ughdance:
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#25 bsico

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Posted 07 July 2008 - 10:47 AM

I know this is an old thread, but I had the EXACT same problem this weekend. My factory battery died after 5 years and 100k miles of dedicated service. After replacement, the engine ran like crap. It would stall at stops and the idle was very low. AC seemed not to work right but that was due to the low RPM not running the compressor high enough. I read about cleaning the throttle body and did this for the first time and there was a ton of carbon built up in there. It looked fine from the outside, but opening the butterfly valve revealed a world of black soot. The engine instantly ran better and I haven't had problems since. My understanding is that the computer was compensating for the dirty throttle body nd therefore it ran fine untill it lost power from the battery change and reset back to factory settings.

Moral of the story, clean your throttle body. Some CRC Throttle body cleaner, a toothbrush and a rag work wonders. To do such, remove the air intake tube from the front of the intake (big round tube from air filter) and open the flapper with the engine off and clean the heck out of it and the chamber behind it. Restart may be rough due to the cleaner in there, but it will run great afterwards.

#26 nitrous1

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Posted 15 July 2008 - 10:59 AM

I know this is an old thread, but I had the EXACT same problem this weekend. My factory battery died after 5 years and 100k miles of dedicated service. After replacement, the engine ran like crap. It would stall at stops and the idle was very low. AC seemed not to work right but that was due to the low RPM not running the compressor high enough. I read about cleaning the throttle body and did this for the first time and there was a ton of carbon built up in there. It looked fine from the outside, but opening the butterfly valve revealed a world of black soot. The engine instantly ran better and I haven't had problems since. My understanding is that the computer was compensating for the dirty throttle body nd therefore it ran fine untill it lost power from the battery change and reset back to factory settings.

Moral of the story, clean your throttle body. Some CRC Throttle body cleaner, a toothbrush and a rag work wonders. To do such, remove the air intake tube from the front of the intake (big round tube from air filter) and open the flapper with the engine off and clean the heck out of it and the chamber behind it. Restart may be rough due to the cleaner in there, but it will run great afterwards.


I had the battery disconnected on my 03 Sierra yesterday and now it is running horrible. I'm going to go clean the throttle body after every thing cools off and see if that helps - it sure couldn't hurt.
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#27 nitrous1

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Posted 16 July 2008 - 07:46 AM

I took my throttle body off yesterday and cleaned it thoroughly. My truck now runs much better - smoothest idle it has ever had since I've owned it.
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