Rough idle/ shuddering in idle.

[iboughtatahoe23]

RPMs seems steady, some hairline movement/bouncing but I think that might be normal. I’m having a rough idle or like a shutter every 4 seconds in park it seems like. When I put it in drive it will drop down to 500 rpm and it goes away.

I have done maf sensor, throttle body cleaning, and serpentine belt and idler pulley. Was gonna do plugs. Air filter is good too. What else can I do?

 

[iboughtatahoe23]

I have other threads about potential transmission and exhaust leak issues, but I don’t think either of those can contribute to a Rough idle.

 

[iamdub]

Depending on what you mean by a "shudder", I'd say it could be an indication of a problem. Otherwise, it sounds like normal operation for these things.

 

[OR VietVet]

How old are the plugs and wires? Any CEL?

 

[iboughtatahoe23]

How old are the plugs and wires? Any CEL?

Haven’t been changed since I had the vehicle. So pretty old I assume!

 

[iboughtatahoe23]

At

Haven’t been changed since I had the vehicle. So pretty old I assume!

167k miles

 

[iboughtatahoe23]

Depending on what you mean by a "shudder", I'd say it could be an indication of a problem. Otherwise, it sounds like normal operation for these things.

It’s just when I’m in park idling. A shutter or shake i feel every couple seconds or more

 

[ivin74]

It’s just when I’m in park idling. A shutter or shake i feel every couple seconds or more

I would start with changing out plugs and wires.

 

[Marky Dissod]

I would start with changing out plugs and wires.

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

 

[iamdub]

It’s just when I’m in park idling. A shutter or shake i feel every couple seconds or more

Right. It's probably the norm for these things, so don't get too concerned if there are no other ailments- No DTCs, no funky operation, MPG is where it should be, etc. But, as the others mentioned, you're overdue for some basic maintenance and inspections. A wise (or wise ass?) old man once said "maintenance pays, breakdowns cost". Plugs, wires, induction and PCV cleaning, check fuel pressures, oils/fluids, coolant, rubber parts, charging system and grounds, etc. Don't get the suspiciously cheap spark plugs from Amazon or eBay as they're highly likely to be counterfeits that could wreck your engine.

 

[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