Rough idle/ shuddering in idle.

[Dustin Jackson]

You can replace the fuel injoctors, spark plugs, intake gaskets, exhaust gaskets, cats and O2 sensors, and the fuel pump and it will still idle like shit.

Best bet it to run premium fuel. Or better yet tune your motor to properly accept premium fuel and raise the idle to 600

 

[iboughtatahoe23]

Although I heartily agree with this recommendation, I would ALSO:
check ground wires for solid connections
check alternator & battery with stress / load tests (preferably with every single accessory on all at once)
check fuel pressures at idle, & 2nd gear start if you have that feature enabled
check PCV Valve or orifice-thingy

Passed battery and alternator tests

 

[iboughtatahoe23]

You can replace the fuel injoctors, spark plugs, intake gaskets, exhaust gaskets, cats and O2 sensors, and the fuel pump and it will still idle like shit.

Best bet it to run premium fuel. Or better yet tune your motor to properly accept premium fuel and raise the idle to 600

The idle is 600 stock in park and I do run premium. It idles at 500 when I’m drive

 

[iboughtatahoe23]

Idle doesn’t seem to be affected on the tachometer, but I can feel some shuttering every few seconds. But it’s not struggling to stay started and it’s not dying. Basically shaking without idle change.

 

[Marky Dissod]

Passed battery and alternator tests

Still other tests to do ...

Idle doesn’t seem to be affected on the tachometer, but I can feel some shuddering every few seconds.
But it’s not struggling to stay started and it’s not dying. Basically shaking without idle change.

Change the plugs and wires.
If after that, you still have the same shudder, replace the coils - they're at least as old as the plugs after all.

 

[iboughtatahoe23]

Still other tests to do ...Change the plugs and wires.
If after that, you still have the same shudder, replace the coils - they're at least as old as the plugs after all.

What do you mean by other tests? How can I test the plugs? All that shows on obd is the spark advance. Can I look at fuel trims and stuff too, to diagnose the rough idle?

 

[iboughtatahoe23]

You can replace the fuel injoctors, spark plugs, intake gaskets, exhaust gaskets, cats and O2 sensors, and the fuel pump and it will still idle like shit.

Best bet it to run premium fuel. Or better yet tune your motor to properly accept premium fuel and raise the idle to 600

It’s flex fuel tho ??

 

[iboughtatahoe23]

You can replace the fuel injoctors, spark plugs, intake gaskets, exhaust gaskets, cats and O2 sensors, and the fuel pump and it will still idle like shit.

Best bet it to run premium fuel. Or better yet tune your motor to properly accept premium fuel and raise the idle to 600

So are you implying that running 91 and 93 premium is my issue?

 

[Marky Dissod]

Although I heartily agree with this recommendation, I would ALSO:
check ground wires for solid connections
check fuel pressures at idle, & 2nd gear start if you have that feature enabled
check PCV Valve or orifice-thingy

You said the battery and alternator passed. OK.

You can replace the fuel injectors, spark plugs, intake gaskets, exhaust gaskets, cats and O2 sensors, and the fuel pump and it will still idle like shit.

Best bet it to run premium fuel.
Or better yet tune your motor to properly accept premium fuel and raise the idle to 600RpM.

So are you implying that running 91 and 93 premium is my issue?

He's implying that NOT running premium is your issue.

It’s flex fuel though??

Since E85 burns cleaner than premium (and has higher octane too), maybe run several tankfuls of E85, and see if that cleans things up a bit.

 

[iboughtatahoe23]

You said the battery and alternator passed. OK.He's implying that NOT running premium is your issue.Since E85 burns cleaner than premium (and has higher octane too), maybe run several tankfuls of E85, and see if that cleans things up a bit.

Actually i recall usually only using e85, and then I started using premium 93 and the idle got Worse.
I’m confused now, so run e85: The cheapest gas available… or run premium??

I feel like using premium may be the issue. I could be wrong.

In the mean time I’ll do plugs and wires