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  1. #1
    Jr. Apprentice
    Join Date
    Sep 2008
    Location
    Albany, NY
    Posts
    23

    Red face Rough Idle...No Codes

    i have a 2008 Silverado Crew Cab w/ 5.3 ltr V8. I took it in to the shop for rough idle. They claim no codes came up therefore no issue. Anyone experiencing this issue? Any input of what it may be?
    Vehicle has 28,000+ on it. Getting ready for a trip so i'd like to remedy this issue asap.

    Thanks fellas
    Sean

  2. #2

    Default

    I had a similar problem (see this topic) on an '04, 1500, 2WD, 4.8L, that had 97Kmiles on it when I recently bought it.

    I cleaned the MAF sensor (refer to the linked post) and the Throttle body... also replaced the PLUGS and checked resistance of the wires (which otherwise appeared to be in good condition). After doing all of this (pretty cheaply at that)... the "rough idle" with no codes being present eventually went away.

    Hope you have similar luck...

  3. #3

    Default

    I have an '09 with the 5.3 and less than 10,000 miles. At times my engine will lope at idle. No other problems that I am aware of.
    LFB57
    '09 Silverado 1500, 5.3, 4 Speed
    G80

  4. #4
    Jr. Apprentice
    Join Date
    Sep 2008
    Location
    Albany, NY
    Posts
    23

    Default

    thanks guys.....I'm gonna have a friend of mine perform BG fuel system cleaning...Dealer wants $119.00, claims he can do it for the cost fo the kit.

  5. #5
    Jr. Apprentice
    Join Date
    May 2010
    Location
    Southern Cali
    Posts
    17

    Default

    do you use 87 or 89 octane gas?....and where are you buying it from??.....my '07 silverado 4.8 liter idles ruff on 87 octane gas.......try a full tank of 89 from chevron or mobil......it will humm at idle.

    ---------- Post added at 08:57 PM ---------- Previous post was at 08:55 PM ----------

    i forgot to say in my last post......these newer trucks like 89 octane gas.....i have a '06 2500HD work truck 6.0 liter motor....it also idles ruff on '87 gas......you will be fine on ur road trip man.....use 89 grade ;)

  6. #6

    Default

    I have noticed my 2010 5.3 Flex Fuel motor in the morning does the same thing. I noticed it the day I test drove it, but it cleared up almost immediately. If I let it sit until the rpm drops back down from a cold startup, it is not that bad. I have been running Sunoco 87, but I think I will try the 89 to see how it does when I am done with this tank.

    Thanks for the tip.
    2010 Silverado LT 1500 Extended Cab Z71 4x4
    Summit White
    Cashmere Leather interior
    Line-X Bedliner
    Bushwacker Bed Rails

  7. #7

    Default

    Quote Originally Posted by pvcableguy View Post
    do you use 87 or 89 octane gas?....and where are you buying it from??.....my '07 silverado 4.8 liter idles ruff on 87 octane gas.......try a full tank of 89 from chevron or mobil......it will humm at idle.

    ---------- Post added at 08:57 PM ---------- Previous post was at 08:55 PM ----------

    i forgot to say in my last post......these newer trucks like 89 octane gas.....i have a '06 2500HD work truck 6.0 liter motor....it also idles ruff on '87 gas......you will be fine on ur road trip man.....use 89 grade ;)
    Interesting!

    The owners manual in my truck's glove compartment clearly states that, with the exception of the "SS" model, 87 Octane is recommended for those vehicles which use gasoline. For the "SS" model, 91 Octane is recommended.

    If I am going to have to run 89 Octane, in order to obtain a smooth idle, then GM needs to rewrite (and send notices to every truck owner as well) their specs. In my area, 89 Octane costs a minimum of $0.10/gallon more than regular unleaded... and in many cases it is more than a $0.10 difference. After doing what I did (and referenced in a previous reply)... every once in a great while, as I am sitting at a stop light, the idle will "stumble", but only briefly. So, I won't resort to 89 Octane unless it becomes problematic (and can be cured no other way). Every 3rd fill-up, I've been adding the recommended amount of SeaFoam (to mitigate moisture problems which using 10% ethanol fuel only serves to exacerbate, and to ensure a clean fuel system and injectors).

    All of the above aside... thanks for adding your experiences to this thread!
    Last edited by 04-silverado; 06-24-2010 at 12:46 PM. Reason: had "91" on the brain, after reading owners manual... corrected that to be "89" where necessary

  8. #8
    Jr. Apprentice
    Join Date
    Sep 2008
    Location
    Albany, NY
    Posts
    23

    Default

    I do run either sunoco 87 or Hess 87 octane. I live in albany NY and i'm going to New Hampshire this w/e for NASCAR race and i'll be sure to try 89. i'll post an update when i return. Thanks for all the tips fellas.

  9. #9

    Default

    Got this the other day when mine was in for the same thing.............again!
    I think if you click on image and then "save image as" you should be able to enlarge it enough to read.
    Attached Thumbnails Attached Thumbnails idle (Small).jpg  
    Last edited by eyegore; 06-25-2010 at 06:56 PM.

  10. #10

    Default

    Hey, thanks for sharing!

    If S1 diagnosis for Rough, Unstable, or Incorrect Idle have been completed and are inconclusive, this should be considered an idle characteristic of the vehicle and no repairs should be attempted
    Well, isn't that special? GM puts out vehicles costing $30K and much more... which are many decades advanced from their predecessors... and with all this advanced technology... they idle like crap?!

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