Shake or Shudder at Idle???

steve76t · February 10, 2020

Hi All,

I have a 2017 GMC Sierra Denali 1500, 5.3L, 8 speed and about 30,000 miles. Over the last month or so it's started a wierd shudder that only happens at idle, after stopping and sitting at a light for about 15-20 seconds. Almost feels like the truck is about to stall or may be the transmission is shuddering? RPMs don't drop or change from it's normal idle reading. Only lasts about 3 to 5 seconds and goes away as quickly as it started. Doesn't happen at every stop or light, just once and a while. Might happen a couple times during a trip around town, might happen once or twice during an entire work week. Doesn't happen at all while moving.

Anyone else ever experience this?

papageoff · February 10, 2020

I have this too. I cannot find any cause and it's annoying but so far, harmless.

karlmg · February 11, 2020

Bad torque converter or worn engine mounts.

jagabom (Esquire) · February 11, 2020

Some have raised the idle from 500 to 600 with a tune or something like that and their vibration was gone. My 2014 as well. Don't have that truck anymore.

Jim

steelerdude15 · February 11, 2020

I've read somewhere here that our trucks idle below 500 rpm for fuel efficiency and the only way to stop the rough idle is to have the truck tuned to idle higher.

Bob2C · February 12, 2020

Have the same thing on my 2018. Had the mounts replaced. It helped but still there. Got a tuner, raised idle to 600. Smooth as butter now. Have to look at tach occasionally to see if it’s running.

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jagabom (Esquire) · February 12, 2020

23 hours ago, Bob2C said:

Have the same thing on my 2018. Had the mounts replaced. It helped but still there. Got a tuner, raised idle to 600. Smooth as butter now. Have to look at tach occasionally to see if it’s running.

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Can you tell me what kind of tuner you got?

Thanks

Jim

Bob2C · February 12, 2020

Can you tell me what kind of tuner you got?
Thanks
Jim

Got the diablo sport intune i3.

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steve76t · February 13, 2020

stock idle speed? The idle is consistently at about 600 already according to my tach. I was thinking of getting a tuner after the warranty expires. May be more reason to get that sooner than later.

Not sure about motor mounts being an issue. If that were the case wouldn't the rough idle be more consistent?

Bob2C · February 13, 2020

There is a tsb for idle in drive being rough and motor mounts getting changed. That’s how I got mine done. In park it idles at 550, but in drive it would go to 500 and and below. Sometimes 475. Just way too low. I raised it to 600 in drive and left the park idle alone. The tach is not an accurate way to read idle. I had blue driver OBD reader hooked up and watched real-time data. You can leave original tune and just raise idle and turn off afm if you would like but I decided on the 87 tune from diablo and adjusted those parameters. Truck has a bit more response. So far so good after 200 miles. I have 20k miles on mine. Couldn’t take the bumpy idle anymore.

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jagabom (Esquire) · February 13, 2020

If you think the tach is reading 600 and still shuddering, try lightly touching the gas peddle, if the shudder goes away then a raise in idle may be in order.

Jim

steve76t · February 14, 2020

23 hours ago, jagabom (Esquire) said:

If you think the tach is reading 600 and still shuddering, try lightly touching the gas peddle, if the shudder goes away then a raise in idle may be in order.

Jim

The thing is that this is very intermittent and doesn't happen very often. When it does it only lasts for 3 or 4 seconds & smooths out as quickly as it starts. Sometimes this'll happen once or twice during a 15 mile commute to work, sometimes it only happens once or twice in a whole week.

steve76t · February 14, 2020

On 2/12/2020 at 6:15 PM, Bob2C said:

There is a tsb for idle in drive being rough and motor mounts getting changed. That’s how I got mine done. In park it idles at 550, but in drive it would go to 500 and and below. Sometimes 475. Just way too low. I raised it to 600 in drive and left the park idle alone. The tach is not an accurate way to read idle. I had blue driver OBD reader hooked up and watched real-time data. You can leave original tune and just raise idle and turn off afm if you would like but I decided on the 87 tune from diablo and adjusted those parameters. Truck has a bit more response. So far so good after 200 miles. I have 20k miles on mine. Couldn’t take the bumpy idle anymore.

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thanks for the input. I've got to get the truck into the dealership anyway to fix a low reading fuel gauge so hopefully they can look into this as well. As intermittent as my issue is I'm not gonna count on them actually fixing it. But ya never know...

I'll consider the tuner regardless...