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#1
08-21-2004, 10:27 AM
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Please Help 1999 Silverado!!!!
I have a 1999 Silverado Z71 Ext Cab. 113,000 miles. After it sits overnight, I start it and it idles really bad like it is going to die, but it doesn't. If I let it run for about 5-8 minutes it is fine all day. If I don't let it sit for awhile, then when I put it in drive it lags and sputters for a second or two and then it is fine all day. Fuel filter, air filter, PCV valve and spark plugs have been replaced. All 9 computer updates have been applied. Fuel pressure regulator tested fine as well. Fuel pump doesn't whine or show any signs of failure. There are also no codes showing in the message center, and no codes show up when GM tech hooks up diagnostics to it. What could be the problem???
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#2
08-21-2004, 05:43 PM
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Re: Please Help 1999 Silverado!!!!
Hey Mulaka Which 9 Computer Updates Are You Talking About. I Never Received Any Notices On This. I Have A 99 Silverado Ext. Cab. With 113,659 Miles.
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#3
08-21-2004, 06:07 PM
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Re: Please Help 1999 Silverado!!!!
I agree with powerdrill, I think some mechanicīs been charging you for something that he hasnīt done, but anyway, the sputters or noises you hear could be piston slap, I have seen many posting wher the vortec engine is experiencing this and that even GM has bought back some trucks. GM doesnīt know what it is and our engines may be doomed to a shorter life because of this.
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#4
08-21-2004, 06:13 PM
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No, they are ligitamate updates. Go to the Chevy dealer and ask them to run your VIN number to see if any of the updates have been applied to your truck (if it is used), if you are a one owner you should know. They hook up to the truck and put them into your computer. They printed off the codes for me to explain what each one was for. There was one for a the transmission shifting hard, one for driveability concerns such as rough idle etc. It only cost $47.00 to do it. I don't have any kind of piston slap or noise or knock. Just the cold start rough idle (sometimes) and then when you put it in drive it doesn't respond right away(1-2 seconds) then it sputters on and is fine until the next morning cold start.
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#6
08-22-2004, 10:13 AM
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Re: Please Help 1999 Silverado!!!!
Have you tried different fuel additives? Maybe run a higher octane or even add some Fuel injector Cleaner?
__________________
 2008 GMC ACADIA SLE Edition, 7 passenger model I AM Canadian!! 
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#8
08-22-2004, 10:56 AM
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What octane fuel are you using? You should be using regular 87 octane..using a higher octane could cause some cold driveability issues.
Is this the old body style or the new body style? Since you say Silverado, I'm going to assume this is the new body style with the 5.3 or 4.8 engine. First I would look at the condition of the throttle body..a good cleaning may help. Next I would check fuel pressure..is it bleeding down or slow to build on start-up. Next I would check the sensor data to the PCM..you may have a sensor (CTS, MAP) that is a little schewed causing your concern.
__________________
Why do you never have enough time or money to do the job right the first time, but enough time and money to do it again? Got all the certifications 25 years ASE Certified Master Technician GM WCT Yea..I work at a DEALERSHIP....got a problem with that? Want to diagnose cars like the Pros? FOR SALE: OTC Perception 2 channel Labscope (badged as a Matco Reality) This is my personal labscope that I use to diagnose waveforms, like new, comes with leads and training video PM Me for details
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#9
08-22-2004, 10:59 AM
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Re: Re: Please Help 1999 Silverado!!!!
Quote:
You will not recieve notices of calibration changes. These changes were made to address concerns on these vehicles that could be fixed by a change in software calibrations..usually these changes are referenced in a TSB from GM.
__________________
Why do you never have enough time or money to do the job right the first time, but enough time and money to do it again? Got all the certifications 25 years ASE Certified Master Technician GM WCT Yea..I work at a DEALERSHIP....got a problem with that? Want to diagnose cars like the Pros? FOR SALE: OTC Perception 2 channel Labscope (badged as a Matco Reality) This is my personal labscope that I use to diagnose waveforms, like new, comes with leads and training video PM Me for details
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#10
08-22-2004, 11:57 AM
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I use the regular grade gas..nothing higher because the owners manual says no too. Fuel pressure is good...strong. Haven't checked the throttle body yet. Where is it and how do I clean it?
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#11
08-22-2004, 11:58 AM
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Re: Please Help 1999 Silverado!!!!
I run 91 Octane in my 5.3 L and it seems to like it. I've used STP Fuel Injector cleaner in the past and I've noticed an increase in power, starting, and smoothness afterwards.
__________________
2008 GMC ACADIA SLE Edition, 7 passenger model I AM Canadian!!
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#12
08-22-2004, 07:46 PM
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Re: Please Help 1999 Silverado!!!!
What oil are yuo using?
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#14
08-22-2004, 09:32 PM
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Re: Please Help 1999 Silverado!!!!
If you want to know about your vehicles calibration go here http://calid.gm.com/vci/VINEntryPre.do
__________________
06 Toyota Tundra Double Cab
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#15
08-24-2004, 10:44 AM
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Since doing the computer updates, the idle is normal now. When I put it in drive though, I still get a quick 1-2 second stall and then it goes fine. Would a good dose of STP Fuel Injector Cleaner maybe fix this? Read the very first post to see what all I have done so far.
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