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2020 Silverado Idle RPM adjustment question

PSUFAN
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PSUFAN Enthusiast

PSUFAN

Posted
Posted

I love everything about my 2020 Chevy Silverado 1500 LT 4WD except for the low idle RPM (500) when in park or at a stoplight.  The engine doesn't cut out, but it acts like it wants to and the cabin vibrates just enough to be extremely irritating.  I've talked to 2 dealerships about the issue and asked if they could increase the RPMs to approx. 600-650 RPMs, but they both declined saying that 500 RPMs is the factory setting and therefore no need to change. Any suggestions?  Would increasing the idle RPMs eliminate the slight vibration and provide a smoother idle?  All suggestions are welcome.

reardiff Enthusiast

reardiff

Posted
Posted (edited)

Actually Disregard - I was going to comment on a hand held tuner but just realized tuning isn't available yet on the 2019 +  For what it's worth I have  the diablo tuner on my 2017 and have the idle RPM set at +100 for same reasons you mention and is perfect now. Sorry couldn't be of more help. 

Edited by reardiff
newdude Senior Enthusiast

newdude

Posted
Posted

Nothing to worry about.  No need to change.  

 

If you really truly most definitely wanted to, it would set you back about $2000 for an unlocked ECM and HP Tuners credits.

ftwhite Enthusiast

ftwhite

Posted
Posted (edited)
31 minutes ago, newdude said:

If you really truly most definitely wanted to, it would set you back about $2000 for an unlocked ECM and HP Tuners credits.

Why $2000? Wouldn't it just be $300 for a HP MPVI2, and 10 credits for a 2020 Silverado 5.3/6.2? So around $800. 

That should unlock the ECM and allow for idle RPM programing. 

 

BTW: my 2018 6.2L with 50k idles at 500, and is so smooth I sometimes wonder if it is on at stops. If yours vibrates, I'd wonder if there is a problem (fouled spark plugs, plugged injectors, clogged air, etc).  

Edited by ftwhite
redwngr Senior Enthusiast

redwngr

Posted
Posted

If it doesn't idle correctly they dealer should be diagnosing and correcting the cause.  (and I don't mean covering it up by changing the idle from gm spec)

 

Clearly they don't all idle roughly as described. 

 

calgator73 Senior Enthusiast

calgator73

Posted
Posted

When I test drove two different trail boss with the 6.2 one idled smooth as glass and one was really bad.  Right before my at4 bit it (valve spring).... The idle quality was crap.  Definitely not normal

newdude Senior Enthusiast

newdude

Posted
Posted (edited)
11 hours ago, ftwhite said:

Why $2000? Wouldn't it just be $300 for a HP MPVI2, and 10 credits for a 2020 Silverado 5.3/6.2? So around $800. 

That should unlock the ECM and allow for idle RPM programing. 

 

BTW: my 2018 6.2L with 50k idles at 500, and is so smooth I sometimes wonder if it is on at stops. If yours vibrates, I'd wonder if there is a problem (fouled spark plugs, plugged injectors, clogged air, etc).  

 

New ECMs are way different than your 2018.  You have to buy an unlocked ECM from HP Tuners and then the 10 credits.  Its $1400 just for the unlocked ECM.  

 

L84 & L87 – E90 Modified ECM Exchange Service – HPTuners

Edited by newdude
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ftwhite Enthusiast

ftwhite

Posted
Posted
14 hours ago, newdude said:

 

New ECMs are way different than your 2018. 

Good point.

So maybe OP can call one of the 'plug in' tune companies (SuperChips, Diablo, etc) and see if they have a solution. Since some of their solutions just override ECM values in "real-time" and are advertised as working on 2019+, maybe they have a config that can set the idle speed? They disable DFM/AFM that way. 

Or, find a dealer that is willing to set the idle speed.

Or, find a non-dealer with GM approved equiptment. 

 

Just thoughts. 

redwngr Senior Enthusiast

redwngr

Posted
Posted (edited)

Vibration at idle...

I still think it is in need of a repair.

 

https://gm-techlink.com/?p=14637

Vibration or Rough Idle in Drive or Park

April 13, 2021

A rough idle or vibration at idle may be present with the transmission in Drive or Park on some 2019-2021 Silverado and Sierra models equipped with the 5.3L V8 engine (PRO L82, L84) or 6.2L V8 engine (RPO L87). (Fig. 15) The idle condition may be most noticeable when the engine is completely warmed up and accessories are off. There may be several possible causes: misfire or an engine concern, wrong fuel used, idle speed fluctuation, or engine mount pre-load.

 

F15-rough-3-C.pngFig. 15

 

To correctly diagnose the potential sources of the idle condition, use the CH-51450 PicoScope oscilloscope following the procedures outlined in #PIP5798.

Begin diagnosis by checking for stored DTCs. Any DTCs should be addressed first. Also confirm there are not any illuminated warning lamps on the instrument cluster.

Next, monitor fuel trim readings and cylinder misfires to confirm there are not any engine concerns. Note the idle speed at this time.

In addition, if premium fuel is required, confirm that it is being used instead of regular fuel.

Perform an analysis using the PicoScope with a single axis sensor or a tri-axis sensor to measure the vibration disturbance frequency at the seat track. (Fig. 16) If the measurement is above the acceptable threshold, perform the Engine and Transmission Mount Settling Process covered in #PIP5798.

 

F16-rough-2.pngFig. 16

 

Any engine mount-to-frame bolts removed during this process must be replaced with new bolts. Both the left-hand and right-hand engine mounts need to be seated to the vehicle frame at the same time to ensure the best alignment. Do not use an impact wrench. Torque the new bolts to specification in sequence. (Fig. 17)

 

F17-rough-1.pngFig. 17

 

If the disturbance frequency measurement does not improve after completing the settling process, replace the powertrain mounts. Before replacing engine mounts, check that the exhaust system is not bound up and that the rear transmission mount is clear of any debris and not damaged. Either of these can result is a higher than normal PicoScope measurement.

TIP: If the vibration condition was corrected following the procedures in #PIP5798, print and attach the “before and after” PicoScope measurements to the repair order. If the vibration condition is still not acceptable after completing the settling process or replacing the engine mounts, open a TAC case and attach your files to the case. Refer to #PIP5601A to upload the files.

For parts information and complete details on the Engine and Transmission Mount Settling Process, refer to #PIP5798.

 

Edited by redwngr
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SteveCZ Enthusiast

SteveCZ

Posted
Posted

I realize this isn't totally related, but I had a similar issue on my 2014 Sierra.  They attempted the alignment, then had to swap one of the mounts.  The truck only had maybe a few thousand miles on it, and did it from day one.  After the fix, you couldn't tell the engine was running.  Just my $0.02

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