07yukon Denali rough idle

[Chris2144]

I’ve been away from this forum for a while but here I am back with another vehicle, I have a few issues with.

It a 07 Denali with the 6.2
Rough idle when warmed up
It will idle just over 500 and it’s rough enough that the rpm’s jump around a little.
As soon as I picked it up I replaced plugs and wires. This seemed to help a bit it’s still there.
The next plan of action is clean the Maf
Clean the throttle body
Run decarbon on it.

There are no codes fuel mileage seems decent about 19

I am replacing the torque converter due to shuddering when driving but I don’t think that has anything to do with the rough idle.

Any other things to check out on this?

 

[Fless]

Verify fuel rail pressure and check fuel trims at idle and 1800 rpm.

 

[Chris2144]

Fuel rail pressure is 58psi.
I’ll check the fuel trims.
Anything else to check while I have the scanner on it

 

[solli5pack]

Check for misfires and misfire history. Shouldn't be much if its running well.

 

[Chris2144]

Ok will check fuel trims and misfires.
It didn’t have any codes no random or single cylinder misfires

 

[Chris2144]

It’s been a min but I got tied up replacing the torque converter.
Now that it’s done I can move on to the numerous other things that have been neglected on this vehicle.
I checked misfires I have none.
I checked fuel trims bank 1 is 11.2
Bank 2 is 12.5
I’m suspecting I have a vacuum leak. I checked all the normal suspect areas break booster pcv ect.
I am suspecting it’s the intake gaskets.
I have not sprayed to confirm this.
I did clean the throttle body and the maf.
That did help a little bit the idle is a bit smoother now but still not quite perfect.
Fuel mileage is still surprisingly decent 18-19 on the highway

 

[SpareParts]

I never have much luck spraying an intake looking for a leak. Seems like the leak is always underneath where you can't get to.

 

[Fless]

A vacuum leak is easier to diagnose if the fuel trims are checked at hot idle, then again at 1800-2000 rpm. If they are over 10% or so at idle but significantly decrease at the higher rpm, a vacuum leak is a distinct possibility.

 

[rdezs]

How many miles on the engine? Age of the fuel injectors is a common culprit in a rough idle. A set of properly remanufactured injectors, flow tested and such, is reasonable in price compared to brand new ones. Here's the guy I use, he sells on eBay:
https://ebay.us/m/togiRm
Fuel injectors

I've used him multiple times, different vehicles, never an issue. Check his feedback ratings as usual.

 

[Chris2144]

I will check hot idle fuel trims and at 1800 rpm.
When I had the exhaust off to do the torque converter I shined a light down the cars and they don’t look clogged or have much oil gunk and the engine is plenty powerful.
I’ll try and rule out a vacuum leak before ai replace injectors.
Engine has 161k on it

 

[donjetman]

Leak(s) between the head(s) and exhaust mainifold(s).

 

[Chris2144]

No exhaust leaks.