Shakes and vibration on cold start
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Joined: Feb 2011
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Shakes and vibration on cold start
In stock forum my car has a mild-moderate vibration when starting cold. You can feel it in the seat a little and if you open the door you can see the glass shaking if you look closely. As the engine warms up it goes away for the most part but sometimes when idling you get a couple random shakes of the seat and it comes and goes but is constant when cold. My first guess was fuel injectors being dirty, car has 40K and is an 05. I ran several cycles of pour in injector cleaners but did not help. I am thinking about buying new spark plugs and after that running a direct injector cleaner thru the injectors.
Am I on the right track? What would you best guess be?
Thanks guys!
Am I on the right track? What would you best guess be?
Thanks guys!
Racer
Joined: Feb 2011
Posts: 468
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From: Phillips Ranch California
Mine does the same thing.. I thought it was a miss when I first got the car but after a lot of searching I have come to the assumption that it is normal on the LS3 engine.. (I have an 08 with 28k)
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In stock forum my car has a mild-moderate vibration when starting cold. You can feel it in the seat a little and if you open the door you can see the glass shaking if you look closely. As the engine warms up it goes away for the most part but sometimes when idling you get a couple random shakes of the seat and it comes and goes but is constant when cold. My first guess was fuel injectors being dirty, car has 40K and is an 05. I ran several cycles of pour in injector cleaners but did not help. I am thinking about buying new spark plugs and after that running a direct injector cleaner thru the injectors.
Am I on the right track? What would you best guess be?
Thanks guys!
Am I on the right track? What would you best guess be?
Thanks guys!
Drifting
Joined: May 2008
Posts: 1,663
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My 08 with 13k miles on it does this at idle sometimes as well. I've test driven two other vettes, one an 07 and another an 08 and I felt the same thing.
The cold start thing I recently noticed though, the car had been sitting for a bout two months in the garage (~50 degrees or so) and the initial start it struggled for a like a second. I went to gas up on that same run and at the gas station it did the same thing. I'll haveto check this again when the rain lets up.
The cold start thing I recently noticed though, the car had been sitting for a bout two months in the garage (~50 degrees or so) and the initial start it struggled for a like a second. I went to gas up on that same run and at the gas station it did the same thing. I'll haveto check this again when the rain lets up.
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Cleaned both the first week I had the car just as maintenance. I also changed out the MAF from the LS2 to the LS6 as the LS6 does not use the honey comb so is less restrictive. The car ran better after changing to the LS6 MAF but I still have this issue.
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Yes, CRC makes MAF cleaner. I got a can last year at Autozone and used it on a few cars. It seemed to help.
Below a certain coolant temp, the PCM in open loop and the NB02 feed back is not part of the fueling equation. My car was set at the factory that the coolant temp has go above 131°F degrees to go into closed loop. In other words, the fueling is done from a series VE, MAF, air temp, and coolant temp tables programed in by the factory (or modified by your tuner).
There are tables to adjust fuel injectors duty cycle based on air and coolant temps. If you've had mods to the intake and exhaust, they may need a small adjustment to increase fuel during low temp because the increase in air flow from the mods results in a leaner a/f ratio during warm up.
Below a certain coolant temp, the PCM in open loop and the NB02 feed back is not part of the fueling equation. My car was set at the factory that the coolant temp has go above 131°F degrees to go into closed loop. In other words, the fueling is done from a series VE, MAF, air temp, and coolant temp tables programed in by the factory (or modified by your tuner).
There are tables to adjust fuel injectors duty cycle based on air and coolant temps. If you've had mods to the intake and exhaust, they may need a small adjustment to increase fuel during low temp because the increase in air flow from the mods results in a leaner a/f ratio during warm up.
Last edited by Mez; Mar 13, 2011 at 09:06 AM.
