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Rough Idle 99 Silverado 5300

cuwdcuwd Member Posts: 2
edited March 2014 in Chevrolet
The idle on my 99 Silverado 5300 V8 vibrates the
seat slightly and the antenna sways about an inch
at top.

Took it back to dealer and they reprogramed but
still the same.

Tried another new 99 Silverado 5300 V8 and it was
slightly better.

This problem of idle smoothness seems rediculus as
my 94 Astro van idles smoother with a V6.

Many vehicles at idle are very smooth.

Anyone else with this problem and is there a fix ?


  • mikey42mikey42 Member Posts: 28
    in it, but it feels more like a miss than a vibration. At first I thought I had a misfire but it runs so smooth beyond idle that I assume its a vibration and not a misfire. I bought my truck to drive not idle so I am ignoring it. Mine is a 5.3 2000 so if you consider it a problem with yours, its not fixed on the 2000's.
  • quadrunner500quadrunner500 Member Posts: 2,721
    My 5.3L (14,000 miles) moves the antenna back and forth only about 1/8" when idling, and no seat shaking.

    Maybe you should try synthetic oil. Sometimes, rough idling can be caused by the EGR valve, or the PCV valve, either one. Or maybe a vacuum leak.
  • haulinhaulin Member Posts: 17
    My 6.0 has a rough idle too, getting slightly worse with time. Going in tomorrow morning, but I don't have my hopes up.
  • cr3cr3 Member Posts: 42
    when i first started mine on the lot it shook badly after advising my salesman[before prep]he had it corrected promtly.seemed to be sour fuel,too low of an idle combo.now its good,but not as smooth as my 5.7 99 3500 van motor.i do love this motor though,the 5.3 is a smooth,powerful engine.making all the power right where you need it.
  • z71billz71bill Member Posts: 1,986
    GM web page at HTTP://calid.gm/vci/

    You put in your trucks VIN # and it will list program updates on your specific truck. I was not having any problem with ruff idle but when I put my trucks VIN in it listed an update. Last time I had the truck in for service I ask the service manager and he went ahead and updated the program. The truck was good before but now runs like silk. I don't understand all this programmable controller stuff but it works, they also updated the program for the transmission - like the idle it was good before but now it is the smoothest shifting automatic I have ever driven... I took the print out in with me

    Hope this helps -
  • haulinhaulin Member Posts: 17
    As mentioned in #3, I took my 6.0L in to the dealer, he met all of my expectations. I didn't expect him to find anything, and he didn't. Still feels like a 4.5 earthquake when sitting at a stoplight. Isn't shaking my coffee out of the cup yet, but it's trying to. Smooth as can be when under power, just suffering from the DTs at idle in gear. Doesn't go away in neutral, but does reduce. He updated the program, if anything it shakes worse now. Truck idles at 500 RPM, tach doesn't move. When I put it in neutral and rev to 1000 RPM it is as smooth as it can be. A/C is off in all instances. Maybe I need to research idle speed a bit.
  • cr3cr3 Member Posts: 42
    it shure sounds like a vacuam leek
  • quadrunner500quadrunner500 Member Posts: 2,721
    The dealer can't be of much help.
  • cuwdcuwd Member Posts: 2
    I talked to several Chevrolet service managers about this nuisance somewhat intermitent idle problem. They could only suggest that I wait maybe a couple of monthes and then they will maybe have another program update for idle problem.

    I tried response #5,s GM Program update index address of HTTP://calid.gm/vci/ and I keep getting
    unable to locate server messages. Maybe the server is down. Anyway it would be interesting to try.
    The dealer will do it for me if I leave the truck.

    The dealers don't want to check basic things like
    vacumn and spark plugs because if they don't find anything they claim they wouldn't get paid by GM.

    Thanks again for your responses and post any news
    on idle problem progress.
  • zbad71zbad71 Member Posts: 226
    You are correct about the dealers not getting paid for troubleshooting. I think my dealer would (and probably all for that matter) be a very good dealer in servicing my truck. However, everytime I have been to my selling dealer I get the same run around. I am friends with one of the techs and he told me that what you say is true....If the shop spends enough time diagnosing a problem and doesn't find the problem, the shop just lost that much money. GM will only reimburse for actual repairs. They will pay for diagnostic time, but only if the result ends in a resolution. Also, if the shop does shoddy troubleshooting and replaces a good part thinking it will fix the problem, GM will not honor further repairs for the same problem. In other words they won't pay for "from the hip troubleshooting". Because a lot of these shops are very inexperienced with the new technologies, especially this LS1 truck, this will be common until they are properly trained and get some experience with them.

    My expereience has been that it is best to find that tech that just graduated from school. They are usually well trained on the latest technologies and they are gung ho to get their hands on everything to gain experience.
  • mckainmckain Member Posts: 20
    I read on one of the recall pages that the 99 silverado had a bad EGR valve in some months during manufacture. You might want to check into this

  • zbad71zbad71 Member Posts: 226
    In all those cases of bad egr valve, the egr valve triggered a computer code. The trucks experiencing rough idle do not have the codes.
  • vince4vince4 Member Posts: 1,268
    Just to add my story to the pile: I have a 2000 6.0L and it has a rough idle. I haven't looked at the antenna but that's a good way to quantify the problem so I'll check. It isn't drastic, but I can feel the engine jumping around a bit. It's just above my tolerance for idle smoothness so it bugs me. I didn't expect it to be as smooth as cars from that island nation, but this is silly. Runs great otherwise.
  • 2sly4u2sly4u Member Posts: 28
    Yeah, I agree. With all the technology, they should be able to build the hp and torque into these engines without the muscle car feel.

    I'd have it checked out.
  • vince4vince4 Member Posts: 1,268
    My antenna tip moves about 1/2 inch at idle. I'll ask the dealer when I go but I don't have a lot of hope.

    I was wondering why it does this and something came to mind. Maybe for emissions reasons they run the mixture lean just until the idle degrades. This is easy to diagnose, I learned the trick looking over my mechanics shoulder. Shoot propane into the air intake and see if the idle smooths out. You need a small propane cylinder with a valve and hose attached. I'm going to try it and will post the outcome.
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