2014 GMC 1500 5.3 uneven at idle

dtreid · April 14, 2020

When warmed up at a stop light, my truck is a little uneven at idle. Does this mean that it is in V4 mode, or something else?

Edited April 14, 2020 by dtreid

Bob2C · April 14, 2020

Nope. It’s just GM’s crap idle. My 18 Tahoe did the same thing. Had motor mounts changed although helped did not solve problem. It idles to low. Got a diablo tuner and raised idle while in drive to 600. Smooth now.

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CamGTP · April 14, 2020

The AFM is not active at idle or at low speeds, so it's not in V4 mode.

Some things may or may not help but are worth trying. You could try cleaning the MAF, the throttle body. If spark plugs have never been changed, maybe consider that. Try some fuel system cleaner for the injectors. Hard to say what it may be but 2-3 of those things are basically free to do.

Toss some premium fuel in the tank and go give it the business for a little while. I'll put a vehicle through the ringer sometimes just to get things cleared out and nice and toasty.

mookdoc6 · April 14, 2020

Nope,nope and another NOPE! GM GDI hot idle mapped in Drive to 500rpm's about 100rpm's to low to be smooth...price you pay for GDI efficiency. GM fuel economy on these V-8's are incredible it's give and take I choose to bump mine up 50rpm's in hindsight 100 would have been perfect.

Edited April 14, 2020 by mookdoc6

Bob2C · April 14, 2020

Nope,nope and another NOPE! GM GDI hot idle mapped in Drive to 500rpm's about 100rpm's to low to be smooth...price you pay for GDI efficiency. GM fuel economy on these V-8's are incredible it's give and take I choose to bump mine up 50rpm's in hindsight 100 would have been perfect.

Did you bump only in drive or when your in park as well? I just did in drive and left in park alone at 500. I was thinking of bringing that to 550. Annoys me but I don’t sit in the truck much while in park.

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BigBadSierra · April 14, 2020

I've been using GDI IVD™ Intake Valve & Turbo Cleaner at every oil change and no idle issues ever.

This included the other direct injection engine like the 3.6 with 80K on it in the Impala that my mother brought to me complaining about the idle I cleared it up with the CDR.

It may take a few treatments to wash the valves off.

LDM · April 14, 2020

4 hours ago, BigBadSierra said:

I've been using GDI IVD™ Intake Valve & Turbo Cleaner at every oil change and no idle issues ever.

This included the other direct injection engine like the 3.6 with 80K on it in the Impala that my mother brought to me complaining about the idle I cleared it up with the CDR.

It may take a few treatments to wash the valves off.

Used this as well recently on my 18 as I noticed a bit of a rough idle at startup in the mornings. It seems to have helped as I no longer have the rough idle since using it.

mookdoc6 · April 14, 2020

9 hours ago, Bob2C said:

Did you bump only in drive or when your in park as well? I just did in drive and left in park alone at 500. I was thinking of bringing that to 550. Annoys me but I don’t sit in the truck much while in park.

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No...the Park idle is fine 600rmps Just bump the Drive idle...is all and your good!

14burrito · October 13, 2020

On 4/13/2020 at 6:14 PM, Bob2C said:

Nope. It’s just GM’s crap idle. My 18 Tahoe did the same thing. Had motor mounts changed although helped did not solve problem. It idles to low. Got a diablo tuner and raised idle while in drive to 600. Smooth now.

Sent from my iPhone using Tapatalk

So I have a stupid question, Can the idle RPM be changed without actually installing one of the canned tunes?

From my understanding, the features built-in to the inTune can only be used when installing one of the canned tunes (making alterations to that). Is this correct? Or can I hook up the inTune and make an idle RPM change and leave the OE file/Cal ID and such in the ECM?

Follow-up question, different train of thought...

I was told by a few that the vehicle can be flashed back to the OE file, take it to the dealer and they would not be able to tell if it had been flashed or not...I find this to be a little odd. Diablo could not answer this question...How is this possible?

Doesn't mode 9 clear/reset with a new SW file being flashed into the ECM? If so, all the dealer has to do is a systems health check, quick overview of collected data and it would otherwise shows X value erased/0 values...which in turn would bring the question of the dealer/GM network not showing a history of this from their side. I assume this would be standard practice for any and all warranty work especially powertrain related. Will they bother with this during a typical LOF, no. But I would assume they would research this depending on what warranty work would be getting completed.

Anyone have info about that?

Edited October 13, 2020 by 14burrito

Bob2C · October 13, 2020

So I have a stupid question, Can the idle RPM be changed without actually installing one of the canned tunes?

From my understanding, the features built-in to the inTune can only be used when installing one of the canned tunes (making alterations to that). Is this correct? Or can I hook up the inTune and make an idle RPM change and leave the OE file/Cal ID and such in the ECM?

Follow-up question, different train of thought...

I was told by a few that the vehicle can be flashed back to the OE file, take it to the dealer and they would not be able to tell if it had been flashed or not...I find this to be a little odd. Diablo could not answer this question...How is this possible?

Doesn't mode 9 clear/reset with a new SW file being flashed into the ECM? If so, all the dealer has to do is a systems health check, quick overview of collected data and it would otherwise shows X value erased/0 values...which in turn would bring the question of the dealer/GM network not showing a history of this from their side. I assume this would be standard practice for any and all warranty work especially powertrain related. Will they bother with this during a typical LOF, no. But I would assume they would research this depending on what warranty work would be getting completed.

Anyone have info about that?

Yes the idle can be changed. That was my original goal using the Diablo sport i3. I then decided to do a custom tune because I already screwed with the ecm so called “watermark”. From the numerous things I read even if flashed back to stock, GM can see the index marks don’t align with what is registered in their system for that vin and will deny warranty for power train issues. I couldn’t take the crap idle so I didn’t care.

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14burrito · October 13, 2020

5 minutes ago, Bob2C said:

Yes the idle can be changed. That was my original goal using the Diablo sport i3. I then decided to do a custom tune because I already screwed with the ecm so called “watermark”. From the numerous things I read even if flashed back to stock, GM can see the index marks don’t align with what is registered in their system for that vin and will deny warranty for power train issues. I couldn’t take the crap idle so I didn’t care.

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Thank you, I will be sending a DM for a few points I would love to hear more from you about.