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Idle surging deemed normal by dealer

Ropegun2k

By Ropegun2k
in Troubleshooting & Recalls

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Ropegun2k Enthusiast

Ropegun2k

Posted
Posted

Hello.  New to forum.   I have some mods I will post on another day.   

 

Anyways.   I have been having an intermittent problem with idle surging in park and stopped.   

 

I have attached a quick video. The truck will do this 80% of the time.   At times when the idle drops there can be shuddering or the AC will blow warm.  

 

Dealership gas has repeatedly said that this is normal operation in sierras.  

 

Can anyone confirn?

23A7A92D-E97F-4B1D-9724-CA938C26D129.MOV

1SLOW1500 Senior Enthusiast

1SLOW1500

Posted
Posted

Hunting for idle. You said in park and stopped, does stopped mean drive or reverse or what gear?

I would clean out the intake tube, maf, and tb. Then do a relearn on that. And see if it idles tight. If not next is (assuming engine temp is 180+) the o2 sensors are reading good. Hard to hit a target idle and afr when they read wrong.

Of course pulling all the codes is first but not e everyone has that ability. 

Oh and not normal at all. But I would guess you knew that dealer what bs. 

Ropegun2k Enthusiast

Ropegun2k

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25 minutes ago, 1SLOW1500 said:

Hunting for idle. You said in park and stopped, does stopped mean drive or reverse or what gear?

I would clean out the intake tube, maf, and tb. Then do a relearn on that. And see if it idles tight. If not next is (assuming engine temp is 180+) the o2 sensors are reading good. Hard to hit a target idle and afr when they read wrong.

Of course pulling all the codes is first but not e everyone has that ability. 

Oh and not normal at all. But I would guess you knew that dealer what bs. 

Park while idling, reverse while stopped, drive while stopped.   

 

Truck is is under warranty.  No codes.    

Paintor Enthusiast

Paintor

Posted
Posted

What are your mods? I heard open headers will do the same thing. Fuel Trim way off also causes it. Intake gasket leaks. Really worn out throttle body....

 

 

Insufficient data for a guess.

 

 

The Zip Senior Enthusiast

The Zip

Posted
Posted

Don't look past a bad alternator.  Back in the day surging was happening to me and I rebuilt the alternator, surging gone.  Take it to a auto parts shop like Pep Boys and get an electrical diagnosis.

Ropegun2k Enthusiast

Ropegun2k

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4 hours ago, Paintor said:

What are your mods? I heard open headers will do the same thing. Fuel Trim way off also causes it. Intake gasket leaks. Really worn out throttle body....

 

 

Insufficient data for a guess.

 

 

No performance mods.  When I said mods I meant with some other accessories.  

davester Senior Enthusiast

davester

Posted
Posted

Exhaust leaks might also do it (either broken bolts on the exhaust manifold, or the seal at the exhaust manifold to pipe flange (at least GMT800 trucks).  And by 'it' I mean throw off the fuel trim numbers, which may cause the idle to vary.  And it'll only throw a code if the ecm hits it's limits for either making the engine rich or lean (typically rich for this problem).

Ropegun2k Enthusiast

Ropegun2k

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Posted
5 hours ago, davester said:

Exhaust leaks might also do it (either broken bolts on the exhaust manifold, or the seal at the exhaust manifold to pipe flange (at least GMT800 trucks).  And by 'it' I mean throw off the fuel trim numbers, which may cause the idle to vary.  And it'll only throw a code if the ecm hits it's limits for either making the engine rich or lean (typically rich for this problem).

No exhaust leaks.   

 

30 minutes ago, silveradosid said:

ac blows warm air, have you checked to see if it is low on freon. the engine will surge if the level is low.

It blows cold 99% of the time.   Only when the idle drops so low the engine shudders is when the ac will act up some.   

 

 

 

I bought this 1500 Denali new in December.   I am a little over 30,000 miles so the factory warranty still applies.   If I work the next two months out of town as intended I’ll be out of the factory warranty range.   

 

I will give the dealership where I bought the truck a call.    I have bought 2 new vehicles within a year from them, they might work with me if I explain the situation.    

 

GM corporate is about useless.  It’s a long story, but I have tried going that route for something bigger earlier this year.    

Ropegun2k Enthusiast

Ropegun2k

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11 hours ago, newdude said:

Not normal.  Get a new dealer. 

 

Looks to me it needs an idle relearn.  Perhaps a sticky throttle body? 

I finally reviewed the dash camera footage.  25 minutes of someone talking on the phone in the truck, then a technician leaning into the window looking at the needle saying “that’s not too bad”.    

 

Yup, need another dealer.  

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