17 Suburban Premier - rough idle when warmed up

[Justin J]

Just purchased a used 2017 Suburban Premier about 2 months ago. I notice that after the car has run for a while and is warmed up, coming to a stop and staying in drive there is a fairly noticeable rough idle. The whole truck gets shaky. The roughness goes away upon shifting to neutral or park.

The dealership looked at it and said "everything seemed normal". They checked all the sensors and all as well. But I feel like this isn't "normal".

Anyone experience something similar to this?

 

[Miami-Dade]

Just purchased a used 2017 Suburban Premier about 2 months ago. I notice that after the car has run for a while and is warmed up, coming to a stop and staying in drive there is a fairly noticeable rough idle. The whole truck gets shaky. The roughness goes away upon shifting to neutral or park.

The dealership looked at it and said "everything seemed normal". They checked all the sensors and all as well. But I feel like this isn't "normal".

Anyone experience something similar to this?

My 16 Hoe does it every so often. I find it idles smoothest on 87 Exxon-Mobil. I never complained about it to the dealer as it happens very infrequently. I just ignore it when it happens. Nobody in my vehicle ever says anything about it.

Before buying my Tahoe I rented a lot Tahoe-Suburban's and all of them had the same idle. If I recall correctly GM raised the idle speed on the 18+ to stop the issue.

I assume it would do it more if your a/c system is off but my a/c system is constantly on so I have no idea on that. I cooler-cold climates I leave it in the high-low [bi-level] position. This way there is no fogging on the windows.

 

[Bob2C]

My 18 did it. Had motor mounts changed which helped but I raised idle to 600 and is smooth. 490 to 500 is way to low of an idle IMO.


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[swabbot]

My 15' use to have the same issue. I ended up replacing the fuel pump (error code finally appeared) and the idling issue went away.

 

[Brad32486]

Depending on mileage I've pondered the idea of carbon build up restricting intake passages. This can be a problem on direct injection engines as port injectors would keep the valve ports clean of carbon by way of fuel spray. I work as a service writer for a premium European luxury brand and know how carbon build can cause this, I just don't know how it applies to GM. We have a process where we hook up a gizmo to the intake and it sprays a bunch of cleaner and dissolves the carbon away so you don't have to do mechanical disassembly. I did this on my 15 Tahoe about a month ago and feel a smoother idle and not the slight wander/surge on partial throttle, so it's something to consider.

 

[Miami-Dade]

Depending on mileage I've pondered the idea of carbon build up restricting intake passages. This can be a problem on direct injection engines as port injectors would keep the valve ports clean of carbon by way of fuel spray. I work as a service writer for a premium European luxury brand and know how carbon build can cause this, I just don't know how it applies to GM. We have a process where we hook up a gizmo to the intake and it sprays a bunch of cleaner and dissolves the carbon away so you don't have to do mechanical disassembly. I did this on my 15 Tahoe about a month ago and feel a smoother idle and not the slight wander/surge on partial throttle, so it's something to consider.

Out of curiosity do you write that service up as a Induction Service?

 

[smokey_mountain]

I used to have a thread here on rough idle which was over 50 pages long (or something close to that). My 2018 Yukon had rough idle when I bought it with 7K miles on odometer, spent endless hours and over $2800 of personal money to fix the rough idle and it was all wasted. Finally found a local dealer who was very aggressive and traded good-optioned Yukon for bare-bones 2020 Tahoe. I was in 26 2018+ Tahoe/Yukons by now. That 2020 truck had a smooth idle and still has it 70% of the time but I found the following (purely subjective but I am just trying to pay back to the users of this great forum):
1) These 2018+ 5.3 engines are incredibly sensitive to gasoline brand. Shell, BP, Costco seem to produce the smoothest idle in North Carolina. Shell is universally hated here and on BTOG but again I am just sharing my experience with 5.3 trucks that I drove extensively for months. I do see poorer mileage on Shell. It got Chevron twice when we were on South Carolina and it was by far and I mean by far the smoothest gas and superior mileage.
2) Contrary to the manual, these trucks do not like 87, they retard so much or even detonate on 87 (not always audible but according to logs it is there). However, they seem to idle best on 87. When I put 93 it seems to give it rougher idle. 89 in also a problem as this is the least selling octane and according to two gas station owners they told me they sell <10% in 89 so that gas is not the freshest (assume it has more sediment too). These are high-compression engines and they should prefer 89 or 93 and they probably do but idle is not the smoothest with 93.
3) I see almost no MPG gain with 89 nor with 93 unless it is Shell. With Shell 89 and 93 the mileage is worse than BP or Costco. With Chevron it is like magic, the truck idles perfect and gas mileage is just 10% better (measure on Fuelly).
4) Exxon gives me rough idle, no matter what octane (again dozens here prefer Exxon and for good reasons, but on my two trucks here in NC Exxon is not it).
4) Gas is not gas and no Federal or State is not tightly regulating the additives and do not monitor every station weekly.

I like the ride that these trucks are producing it is very comfortable but be prepared to live with rough idle. 2020s are also abysmally bad with squeaks and rattles in the cabin my dealer is trying to fix them but really cannot. He has tried 7 times now and it keeps rattling in the dashboard, driver door, center console. The truck is 5 months old and has 11K miles now.

Good luck to us all with GM.

 

[Tahoe14]

I've used silicone spray on my center console with success. Easy cleanup, does not harm any of the plastic. Good luck, stinks you have had two back to back with issues.

 

[gat0r]

what is your idle rpms when that happens?

i am thinking it will be low. (although well within GM spec, LOL)

i had mine raised to 600 from 500 when i tuned mine. similar to what Bob2c mentioned

 

[RobDenali]

I had a rough idle that went away when I did the mobile1 atf Flush and TCM relearn as per the TSB. I noticed the difference immediately

 

[Tiredmechanic23]

I used to have a thread here on rough idle which was over 50 pages long (or something close to that). My 2018 Yukon had rough idle when I bought it with 7K miles on odometer, spent endless hours and over $2800 of personal money to fix the rough idle and it was all wasted. Finally found a local dealer who was very aggressive and traded good-optioned Yukon for bare-bones 2020 Tahoe. I was in 26 2018+ Tahoe/Yukons by now. That 2020 truck had a smooth idle and still has it 70% of the time but I found the following (purely subjective but I am just trying to pay back to the users of this great forum):
1) These 2018+ 5.3 engines are incredibly sensitive to gasoline brand. Shell, BP, Costco seem to produce the smoothest idle in North Carolina. Shell is universally hated here and on BTOG but again I am just sharing my experience with 5.3 trucks that I drove extensively for months. I do see poorer mileage on Shell. It got Chevron twice when we were on South Carolina and it was by far and I mean by far the smoothest gas and superior mileage.
2) Contrary to the manual, these trucks do not like 87, they retard so much or even detonate on 87 (not always audible but according to logs it is there). However, they seem to idle best on 87. When I put 93 it seems to give it rougher idle. 89 in also a problem as this is the least selling octane and according to two gas station owners they told me they sell <10% in 89 so that gas is not the freshest (assume it has more sediment too). These are high-compression engines and they should prefer 89 or 93 and they probably do but idle is not the smoothest with 93.
3) I see almost no MPG gain with 89 nor with 93 unless it is Shell. With Shell 89 and 93 the mileage is worse than BP or Costco. With Chevron it is like magic, the truck idles perfect and gas mileage is just 10% better (measure on Fuelly).
4) Exxon gives me rough idle, no matter what octane (again dozens here prefer Exxon and for good reasons, but on my two trucks here in NC Exxon is not it).
4) Gas is not gas and no Federal or State is not tightly regulating the additives and do not monitor every station weekly.

I like the ride that these trucks are producing it is very comfortable but be prepared to live with rough idle. 2020s are also abysmally bad with squeaks and rattles in the cabin my dealer is trying to fix them but really cannot. He has tried 7 times now and it keeps rattling in the dashboard, driver door, center console. The truck is 5 months old and has 11K miles now.

Good luck to us all with GM.

Mid grade fuel octane is a mixture of the low grade and premium that is mixed at the pump while dispensing. So even if rarely sold its as fresh as the other 2 options.


As far as the rough idle my 16 usually starts that as I get near my oil change time. Every oil change I run seafoam through the TB using the aerosol can. My 16 always idles so much better afterward. Also trans fluid and filter can help if not running a good fluid such as Mobile 1. The converters are known for a stutter and there is a TSB for that. With a tune though the idle can be bumped up just a touch and make it much better. But fuel quality does play a big part of things as well.

 

[smokey_mountain]

@Tiredmechanic23 Agreed, I was thinking about changing ATF in my 2020 with 13,000 miles on it, what Mobile1 fluid is the good one? Many folks really favor Amsoil but GM insisits on Mobil1. I understood that there are several incarnations of Mobil1 ATF. It shifts well but I would like to get factory fill ATF out without killing warranty.

Thank you in advance.

Mid grade fuel octane is a mixture of the low grade and premium that is mixed at the pump while dispensing. So even if rarely sold its as fresh as the other 2 options.


As far as the rough idle my 16 usually starts that as I get near my oil change time. Every oil change I run seafoam through the TB using the aerosol can. My 16 always idles so much better afterward. Also trans fluid and filter can help if not running a good fluid such as Mobile 1. The converters are known for a stutter and there is a TSB for that. With a tune though the idle can be bumped up just a touch and make it much better. But fuel quality does play a big part of things as well.

 

[Tiredmechanic23]

@Tiredmechanic23 Agreed, I was thinking about changing ATF in my 2020 with 13,000 miles on it, what Mobile1 fluid is the good one? Many folks really favor Amsoil but GM insisits on Mobil1. I understood that there are several incarnations of Mobil1 ATF. It shifts well but I would like to get factory fill ATF out without killing warranty.

Thank you in advance.

The full synthetic Dexron Vi fluid. I dunno if they still have it but I got a 16qt case from summit after my trans rebuild for 92 bucks.

I have thought about amsoil but I got to do more research first.

 

[sealandsky]

I used to have a thread here on rough idle which was over 50 pages long (or something close to that). My 2018 Yukon had rough idle when I bought it with 7K miles on odometer, spent endless hours and over $2800 of personal money to fix the rough idle and it was all wasted. Finally found a local dealer who was very aggressive and traded good-optioned Yukon for bare-bones 2020 Tahoe. I was in 26 2018+ Tahoe/Yukons by now. That 2020 truck had a smooth idle and still has it 70% of the time but I found the following (purely subjective but I am just trying to pay back to the users of this great forum):
1) These 2018+ 5.3 engines are incredibly sensitive to gasoline brand. Shell, BP, Costco seem to produce the smoothest idle in North Carolina. Shell is universally hated here and on BTOG but again I am just sharing my experience with 5.3 trucks that I drove extensively for months. I do see poorer mileage on Shell. It got Chevron twice when we were on South Carolina and it was by far and I mean by far the smoothest gas and superior mileage.
2) Contrary to the manual, these trucks do not like 87, they retard so much or even detonate on 87 (not always audible but according to logs it is there). However, they seem to idle best on 87. When I put 93 it seems to give it rougher idle. 89 in also a problem as this is the least selling octane and according to two gas station owners they told me they sell <10% in 89 so that gas is not the freshest (assume it has more sediment too). These are high-compression engines and they should prefer 89 or 93 and they probably do but idle is not the smoothest with 93.
3) I see almost no MPG gain with 89 nor with 93 unless it is Shell. With Shell 89 and 93 the mileage is worse than BP or Costco. With Chevron it is like magic, the truck idles perfect and gas mileage is just 10% better (measure on Fuelly).
4) Exxon gives me rough idle, no matter what octane (again dozens here prefer Exxon and for good reasons, but on my two trucks here in NC Exxon is not it).
4) Gas is not gas and no Federal or State is not tightly regulating the additives and do not monitor every station weekly.

I like the ride that these trucks are producing it is very comfortable but be prepared to live with rough idle. 2020s are also abysmally bad with squeaks and rattles in the cabin my dealer is trying to fix them but really cannot. He has tried 7 times now and it keeps rattling in the dashboard, driver door, center console. The truck is 5 months old and has 11K miles now.

Good luck to us all with GM.

Related to your "rattle in the dash". I've battled the same on my 2019 and (I think) the dealer has finally nailed it down. I actually had two competing rattles (I call it "buzzing"), the first was the "home link" box which is located in the forward section of the overhead counsel. The dealer told me that the mounting screws had "backed out" and the unit was hanging there loose as can be. Since it's buzzed from day 1, I think the factory never tightened them in the first place. The second "buzz" was due to the black box on the windshield ahead of my rear view mirror. It was not properly clipped in due to the wiring bundle being installed incorrectly. I think I see a theme here - The person installing my forward interior at the factory was having a bad day.

 

[Bob2C]

Related to your "rattle in the dash". I've battled the same on my 2019 and (I think) the dealer has finally nailed it down. I actually had two competing rattles (I call it "buzzing"), the first was the "home link" box which is located in the forward section of the overhead counsel. The dealer told me that the mounting screws had "backed out" and the unit was hanging there loose as can be. Since it's buzzed from day 1, I think the factory never tightened them in the first place. The second "buzz" was due to the black box on the windshield ahead of my rear view mirror. It was not properly clipped in due to the wiring bundle being installed incorrectly. I think I see a theme here - The person installing my forward interior at the factory was having a bad day.

Th black box on my 18 was not properly clipped either. Cleaning the windshield one day I found it. Didn’t rattle but wasn’t clipped together. Wonder if it was the same guy. Lol


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