Rough Idle?

[TheBlueBomber]

I've noticed that my sonic's idle is rough when I first start it for the day..it will rev up to about 1300 rpm then go from 1500 to 1100 and so on every half second for up to maybe 45 seconds...until it warms up and then idles normal...only the initial idle is not steady at all. Any thoughts? Ps I am taking it to dealer tomorrow for suspension issue...creaking sound from right front strut

 

[Leverus]

Definitely have the dealer look at it.

 

[Eric Smit]

Definitely have the dealer look at it.

+1.


-Eric Smit

 

[sxero]

Did you ever find out what it was? Mine just started doing it this week. Just like yours, it only affects the first start up of the day. If I start it up in the middle or end of the day it will start up fine, even if it has been sitting off for hours. In my case, it happened the day after I got my tune installed. I am hoping that is not what it is and that it is just a coincidence.

 

[rdss]

If its cold it should idle high and then progressively drop down to normal idle, if its bouncing around bring it in.

 

[Larry]

Edit: Oops, forgot DBW cars don't have that anymore.

 

[sxero]

Right now at least, it appears to be caused or at least aggravated by the tune. I flashed the tune on Tuesday afternoon of last week. From Wednesday through Sunday, the first morning startup would be loud, rough, bouncy, and clicky before eventually settling down to a normal idle. Subsequent startups would be normal. Sunday afternoon, I flashed the stock tune back. This morning, the car started and idled normally the first time.

 

[SuperFudd]

If you have not yet, read the sparkplug string on this forum.

 

[CoHPhasor]

Are you running high octane?
It sounds like there might be some sort of timing/fuel control issue with your tune.

 

[sxero]

Are you running high octane?
It sounds like there might be some sort of timing/fuel control issue with your tune.

Yes, I am. With the exception of the first tank from the dealership, I have run nothing but premium 93 octane gasoline in this car. I have owned the car for 2 months now so there should be no trace of 87 octane anywhere in this car

I am going to check on the spark plug gap this weekend and report back if anything. Thanks for all the replies so far.

 

[Larry]

Yes, I am. With the exception of the first tank from the dealership, I have run nothing but premium 93 octane gasoline in this car. I have owned the car for 2 months now so there should be no trace of 87 octane anywhere in this car

I am going to check on the spark plug gap this weekend and report back if anything. Thanks for all the replies so far.

You can still get bad gas even if it's 93. I have experienced it myself several times.

 

[HareBrained]

You can still get bad gas even if it's 93. I have experienced it myself several times.

+1

Premium sits in the underground tank much longer as far less is sold than Regular. You should be using a gas station that is close to expensive homes. ritzy malls, and BMW dealers. The chances of getting stale gas are far less from those locations.

BTW, the first half-gallon you put in your tank is almost always 87-octane. Common-hose pumps are the bane of motorcycles and "premium" cars. I have to run my bike down to almost empty to minimize the effects of the "contamination".

 

[CoHPhasor]

^ Yea, anytime you can find a pump with separate hoses, pull in!

 

[Eric Smit]

^ Yea, anytime you can find a pump with separate hoses, pull in!

For sure.


-Eric Smit

 

[TheBlueBomber]

I took it to the dealer for a suspension issue and told them to check it out....they said the couldn't find anything wrong...I run 93 in it cause its a turbo car...the loaner they gave me was a 2012 impala ltz and it did the same cold idle thing so I am just assuming it is a Chevy thing..if it gets worse I will bring it back

 

[jchasp59]

I took it to the dealer for a suspension issue and told them to check it out....they said the couldn't find anything wrong...I run 93 in it cause its a turbo car...the loaner they gave me was a 2012 impala ltz and it did the same cold idle thing so I am just assuming it is a Chevy thing..if it gets worse I will bring it back

Mine has this idle problem, except it revs to 3K rpm then settles back down. My car is stock, I have no tune. The dealer, as usual, 'Could not replicate'. I pulled the coil pack and found two springs caught on the lip as described in another thread. Corrected that, changed from 93 octane to 87, and now (about a month later) it's idling much better. But, we also have changed from Summer to Winter blend gasoline recently, so I don't know what changed, and the dealer isn't interested in finding out.

 

[Larry]

I've noticed that my sonic's idle is rough when I first start it for the day..it will rev up to about 1300 rpm then go from 1500 to 1100 and so on every half second for up to maybe 45 seconds...until it warms up and then idles normal...only the initial idle is not steady at all. Any thoughts? Ps I am taking it to dealer tomorrow for suspension issue...creaking sound from right front strut

Have you ever removed the airbox? Vacuum leaks can cause rough idle. Coil pack can cause intermittent idle issues too.