Slightly rough idle at cold start

SHOhobo · July 11, 2015, 10:50:25 PM

New 2015 SHO....2000 miles...9weeks owned....after sitting overnight at startup the engines idle is slightly rough like it has a slight miss....rpm gauge bounces slightly as well..rpms r @ 1K...when I go to start it at my lunch break four hours later no issues...so it is seemingly only after sitting overnight. Any ideas as to what the issue may be?

SHOdded · July 11, 2015, 10:55:25 PM

Very likely normal, as oil/trans fluid/PTU-RDU fluid etc have cooled off to ambient after sitting overnight. So a high idle initially is normal, may be a bit rough, until the fluids start warming up enough.

BiGMaC · July 12, 2015, 01:01:42 AM

Sounds like open loop running before the O2 sensors are heated up and active. Might try a 10 min warm up before driving... Remote start. I do it on principle.

ZSHO · July 12, 2015, 10:14:33 AM

I would agree with SHOdded and BiGMaC,but recall when purchasing my car new that i had the same issues,do you have access to 93 octane gas such as Shell,Exxon,also check all the intake,turbo,intercooler,hoses to make sure all the clamps are tight by using a 8mm socket cause mine where fairly loose from the factory,BTW do a couple of wot pulls now and then cause your car will thank you later,best of luck and keep us updated and welcome aboard. Z

SHOhobo · July 12, 2015, 12:16:20 PM

Thank you all....will chk the clamps....already all over the wot pulls...I am old school...like my farher used.to say...."gotta blow the carbon out of it"...unfortunately the highest octane around my area is 91...been using the Shell Nitro 91 exclusively.

BiGMaC · July 12, 2015, 01:06:02 PM

In my area I tried the new Shell Nitro plus (91 for me too)... I went back to Chevron after 2 tanks. My SHO just seemed to lose the edge it had. The Chevron brought it back. So some experimenting with fuel could help too.

SHOhobo · July 12, 2015, 01:46:41 PM

Interesting....I can't find any Chevron stations in WI....BP, Shell, and Mobil seem to be the only choices around here for top tier fuel.

ZSHO · July 12, 2015, 06:29:17 PM

I would try to monitor the car after every fillup,dont know if you use the same gas station in particular,but definetly would try to experiment different stations in your area because of so many suppliers,BTW was curious on your mpg and check out this thread. Z http://www.ecoboostperformanceforum.com/index.php/topic,354.msg79472/topicseen.html

SHOhobo · July 13, 2015, 11:06:18 PM

Hey ZSHO....due to small town limitations I do use the same Shell station...unfortunately choices r limited...it's either Shell, BP, or Mobil for top tier juice...I recently reset the mpg calc after initial break in....so far the avg is 19.8 but on next fill I am gonna check it manually and compare. I am sure it will go up. Also I take back roads to work and they have awesome corners and elevation changes so needless to say I am in sport mode. Interesting post...have u experimented with E85?

ZSHO · July 14, 2015, 09:30:10 AM

Quote from: SHOhobo on July 13, 2015, 11:06:18 PM
Hey ZSHO....due to small town limitations I do use the same Shell station...unfortunately choices r limited...it's either Shell, BP, or Mobil for top tier juice...I recently reset the mpg calc after initial break in....so far the avg is 19.8 but on next fill I am gonna check it manually and compare. I am sure it will go up. Also I take back roads to work and they have awesome corners and elevation changes so needless to say I am in sport mode. Interesting post...have u experimented with E85?

I actually have not but many members have seen not only better performance but cured there hesitation issues with the mix,actually my E85 mix and track meetups for the summer have been halted due to a cracked windshield,best of luck. Z

14 TUX BL · July 21, 2015, 11:15:41 AM

Quote from: SHOhobo on July 11, 2015, 10:50:25 PM
New 2015 SHO....2000 miles...9weeks owned....after sitting overnight at startup the engines idle is slightly rough like it has a slight miss....rpm gauge bounces slightly as well..rpms r @ 1K...when I go to start it at my lunch break four hours later no issues...so it is seemingly only after sitting overnight. Any ideas as to what the issue may be?

Same exact thing with my car.

Bought my used '14 SHO a few months ago with 28k, now have 34k and just switched to Top Tier gas while having the BG Fuel Induction Service done. Slight cold start stumble is still there, ok after brief warm up.

I'll try to get a vid clip of it ...

14 TUX BL · July 21, 2015, 02:39:15 PM

Camera battery died, maybe try again later to vid wavering cold start idle.

Meanwhile, went ahead and checked any turbo clamp I could see with the 8 mm (most needed several turns to tighten).

Then checked the tube without the clamp (pic is from another forum member), seemed fairly tight but looked like it was starting to flare so I simply cut a 1/2" of the end and reattached.

14 TUX BL · July 22, 2015, 01:03:57 PM

Quote from: SHOhobo on July 11, 2015, 10:50:25 PM
New 2015 SHO....
2000 miles...
9weeks owned....
after sitting overnight at startup the engines idle is slightly rough like it has a slight miss....
rpm gauge bounces slightly as well..
rpms r @ 1K...
when I go to start it at my lunch break four hours later no issues...
so it is seemingly only after sitting overnight ...

Like this?
=98121514&filters[recent]=1&sort=1&o=0]http://s667.photobucket.com/user/ProfessionalFirefighter/media/S7300457_x264_x264.mp4.html?filters[user]=98121514&filters[recent]=1&sort=1&o=0

Overnight cold start
Using Top Tier gas for several weeks
BG Fuel Induction Service done
Clamps tightened
Waste gate vacuum hose tight

FoMoCoSHO · July 22, 2015, 01:42:45 PM

Mine does it as well but it's intermittent.

ecoboostsho · July 22, 2015, 02:47:08 PM

My 2013 does this as well. It goes right away once it warms up...never bothered me much but it bothered me enough to monitor for misfires but it wasn't missing so I assumed it was "normal".