Fixed rough idle

Ozer · December 8, 2017

1 hour ago, Obscenejesster said:

I was actually told that GM recommends the BG service every 15k miles on GDI engines.

Is there any truth to this? I have heard that it is very good for GDI engines.

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I got it done at 97k miles, it was the first time for the truck. I didnt feel anything different nor did i get better mpg, but im sure it did what it was supposed to do.

15k mile is way overkill i think. Just run top tier gas vs no-name.

Obscenejesster · December 8, 2017

I got it done at 97k miles, it was the first time for the truck. I didnt feel anything different nor did i get better mpg, but im sure it did what it was supposed to do.
15k mile is way overkill i think. Just run top tier gas vs no-name.

I agree. I'll probably do it at 30k

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Chris Lee · April 2, 2019

On 09/12/2017 at 3:23 AM, gone_fishing said:

I raised my idle +50 RPM with my Diablosport intune i2 and that made the engine a lot smoother when sitting at a stoplight in gear with the AC on. In my opinion, GM just made the idle RPM too low.

Hi, what is your idle at park/neutral?

Chris Lee · April 2, 2019

On 09/12/2017 at 2:51 AM, fondupot said:

When I had my 2014 sierra, the only thing that fixed my rough idle was raising idle RPM to 600 with a Blackbear tune. Never had issues after that. 500 rpm is just too low.

Hi. Would like to know your normal rpm during Park is 500rpm?

Edited April 2, 2019 by Chris Lee

gone_fishing · April 2, 2019

14 minutes ago, Chris Lee said:

Hi, what is your idle at park/neutral?

Warmed up in park/neutral about 550-600 RPM's. This is with the tune.

Chris Lee · April 2, 2019

1 minute ago, gone_fishing said:

Warmed up in park/neutral about 550-600 RPM's. This is with the tune.

My 2010 suburban LT 1500 idles at 550 to 600, but I have a rough idle. :-(

Gagliano7 · April 12, 2019

Berryman b-12 chemtool was the best fuel injection cleaner i used to clean carbon off the top of pistons on a short block i was cleaning up. I tried all different cleaners including Seafoam and the Berryman B-12 Chemtool after sitting on the piston for 10 minutes the carbon just wiped off.

diyer2 · April 12, 2019

I have used them all except the Liqui Molly.

I use Sea Foam the most because I don't let things get bad.

Berrymans B12 is stronger than Sea Foam.

I'm careful where I use it.

BG is to expensive but it is a good product.

greystone · April 12, 2019

I just had my truck in for a faulty fuel gauge. While in they did a ECM update. From what I understand one of the updates was to address rough idle. The update changed idle timing and swear I sometimes have to look at the tac to see if it is running. It's extremely smooth now.

L86 All Terrain · April 12, 2019

I have been in many K2's that do it right from the dealer lot with 10 miles on them, are you suggesting they too need an intake/valve cleaning?

I would be more willing to bet it is just an attribute of these very high compression, high output V8's at a lower than normal idle speed, or stiff rubber engine mounts. Could be due to the cam profile? I wouldn't think so much because the cam specs are very similar to the outgone LS versions that were seemingly smoother. The motor mounts are designed to be smooth at operating rpm, they aren't tuned to be the smoothest at idle and go from there.

Hop in a truck with a Gen3 small block, like a 350hp 383 Stroker with a street cam, it will make these new trucks with 420hp feel like a sewing machine.

I could be out to lunch on this, but I have noticed BRAND NEW trucks idle in the same manner so I have hard time thinking an intake clean would make much of a difference at all.

MeanGreen1911 · April 12, 2019

My G8 with L76 6.0L idled rough from the start. It is a known "problem" to some people but it doesn't bother me. I have not opened it up for a cam and other goodies yet so a little bump while sitting at a stop light just makes me want to cam it even more. The G8 does not idle as low as my Sierra though...I am betting that is a large part of it.

Slash L86 · April 20, 2019

On 4/12/2019 at 9:02 AM, greystone said:

I just had my truck in for a faulty fuel gauge. While in they did a ECM update. From what I understand one of the updates was to address rough idle. The update changed idle timing and swear I sometimes have to look at the tac to see if it is running. It's extremely smooth now.

Interesting. Please tell me what type truck you have and is there a TSB # associated with this update?

I have a 2018 L86 and the slight rough idle is pretty irritating and I believe is causing me to have OCD. Been that way since new and 3,900 on the clock now.

Just want it to be gone so I can feel better that it's not an internal issue causing it.

Thanks

Hello to everyone. Thanks for your support

Nitrousbird · April 20, 2019

The L86 in my '18 has an ever so slight rough idle. Way less than the L92 my Escalade EXT had (the L92 was plagued with rough idle issues - some were seemingly impossible to resolve).

The L86 isn't bad enough for me to worry much about; I'll see if it gets worse (only 2600 miles on her) and have the dealer deal with it. My faith in dealerships is low, and the issue isn't enough to be concerning, so come closer to warranty expiration, I will simply tune her with HP Tuners where bumping the idle will be one of the changes.

hirdlej · April 30, 2019

On ‎4‎/‎12‎/‎2019 at 11:02 AM, greystone said:

I just had my truck in for a faulty fuel gauge. While in they did a ECM update. From what I understand one of the updates was to address rough idle. The update changed idle timing and swear I sometimes have to look at the tac to see if it is running. It's extremely smooth now.

Greystone, would you mind grabbing your invoice for this visit and sharing with us any information that pertains to getting the ECM updated for a batter idle? I'd rather my dealer start with doing something like this before we throw motor mounts and other stuff at it. My truck has 10k miles and runs smooth in rhythm but rough in feeling. Your help is greatly appreciated!

SteveCZ · May 11, 2019

So, I recently did a seafoam treatment in the oil for 400 miles, then, this past tank of gas, I found the Liqui-Moly at AutoZone. I had a slight jiggle when warm at idle at full stop (stop light). After about a third of a tank of gas, the idle is already better, going to take it for a road trip today up and down some good hills. See how it does. Keep you posted