Random Rough Idle

[KY91]

Hello everyone,

First time poster, and not a tuner by any sort, but just started to play around with my mpvi2.

Vehicle: 2016 GMC YUKON XL 5.3. Stock engine, I've only disabled DOD.

Issue I'm having is a having a random shake at idle, and I know it's not uncommon for these for various reasons. I uploaded a log file just to see if anything sticks out to you guys. I'll get a couple random misfires here and there, which I know is not uncommon to see. I've also noticed the LP fuel pressure drop into the 30 PSI range from time to time.

Any pointers or help to lead me in the right direction would be greatly appreciated.

-Keith

3-3-22.hpl

[5FDP]

In my opinion that is fairly common with the stock idle rpm. It's too low and that is why you feel it. I've heard of many people complain about it on other forums as well.

I just raise the rpm to 650rpm while at idle and it smooths way out.

[KY91]

Ok, Thanks! I just upped the idle in a few spots. Wanted to do that on cold start ups anyways. Will do some more logging when I make my way back home. Just wanted to see if anyone saw anything out of whack.

The help is much appreciated!

[Dominatorstang]

I have a L86 and it is about the only in depth experience I have on a Gen V, but some experience with some older Gens. The 500rpm idle was news to me with the L83's. I seen it in the stock tune now too though.

Looking over your log I did find it a bit odd for the misfires since they were off idle and in gear. Bank two is pulling out a bit more fuel than Bank 1, but nothing too crazy. Just enough to take notice though. Misfires are on both banks though and both banks are pulling out enough fuel to take notice but not exactly uncommon. How many miles on the engine and how old are the plugs? What work has been done around the stock engine like exhaust, intake box?

[mbaskett]

Honestly, a tad bit of a random shake at idle for a DI engine that's 5-6 years old is probably due to the fuel system needing a cleaning, unless you have other symptoms that may indicate a more severe issue. I'd run some DI cleaner through the next several tanks of gas and see if it improves.... (follow the instructions; I err on the side of more cleaner per gallon of fuel than recommended by up to 50%)

I have this delivered every 2 months with Amazon's subscribe and save program... https://www.amazon.com/gp/product/B071Z6GPRN

To be fair (to be faaaaaiiirrrr for my Letterkenny folks), I have a collapsed DOD lifter in my 2016 5.3 currently awaiting the last few parts to begin surgery, so my experience with the idle shake like yours may be due to a different cause, but I have always been a firm believer of fuel system cleaners in ALL of my vehicles. Clogged injectors are pervasively nasty buggers.

[KY91]

I have a L86 and it is about the only in depth experience I have on a Gen V, but some experience with some older Gens. The 500rpm idle was news to me with the L83's. I seen it in the stock tune now too though.

Looking over your log I did find it a bit odd for the misfires since they were off idle and in gear. Bank two is pulling out a bit more fuel than Bank 1, but nothing too crazy. Just enough to take notice though. Misfires are on both banks though and both banks are pulling out enough fuel to take notice but not exactly uncommon. How many miles on the engine and how old are the plugs? What work has been done around the stock engine like exhaust, intake box?

All stock. 138k on the clock. All stock. Have recently replaced all plugs and the 5 coil due to failure. I have also replaced the drivers side engine mount due to what appeared to be excessive play.

Idle has been bumped up to 650, and I upped it a little higher for cold starts in low temp ranges. Can still feel it here and there. At idle in park as well as in drive. Seems a little better.

[KY91]

Honestly, a tad bit of a random shake at idle for a DI engine that's 5-6 years old is probably due to the fuel system needing a cleaning, unless you have other symptoms that may indicate a more severe issue. I'd run some DI cleaner through the next several tanks of gas and see if it improves.... (follow the instructions; I err on the side of more cleaner per gallon of fuel than recommended by up to 50%)

I have this delivered every 2 months with Amazon's subscribe and save program... https://www.amazon.com/gp/product/B071Z6GPRN

To be fair (to be faaaaaiiirrrr for my Letterkenny folks), I have a collapsed DOD lifter in my 2016 5.3 currently awaiting the last few parts to begin surgery, so my experience with the idle shake like yours may be due to a different cause, but I have always been a firm believer of fuel system cleaners in ALL of my vehicles. Clogged injectors are pervasively nasty buggers.

I did run some cleaner through it about 3k miles ago. I was thinking of getting some more and like you said giving it a little more than the recommended. I generally use BP gas, so I did try a few different brands and didn?t result in any change.

Normal driving has no issues. Can drive like a grandma or back when I was 16 and it functions properly. I have thought about the lifters, which is why I obviously wanted to disable the DoD. But I feel if one was collapsed I would have issues while driving as well?

[cadillactech]

There are updated engine mounts to fix this concern, both sides need to be done with the updated part number to help dampen the 1.5 engine order vibration.

[KY91]

There are updated engine mounts to fix this concern, both sides need to be done with the updated part number to help dampen the 1.5 engine order vibration.

I did the driver's side and loosened all mounts, including trans and did the "reset" procedure or whatever you want to call it, where you engine brake and retighten the bolts. The vibration in drive has calmed down from what it was before since raising the idle.

[cadillactech]

Ya, if you do both the mounts and the power train settling procedure you can usually get the vibration completely gone with the stock idle settings but raising the idle will do it too.

[mbaskett]

I did run some cleaner through it about 3k miles ago. I was thinking of getting some more and like you said giving it a little more than the recommended. I generally use BP gas, so I did try a few different brands and didn?t result in any change.

Normal driving has no issues. Can drive like a grandma or back when I was 16 and it functions properly. I have thought about the lifters, which is why I obviously wanted to disable the DoD. But I feel if one was collapsed I would have issues while driving as well?

In my experience, a noticeable degradation due to a collapsed DOD lifter is hit or miss, and all depends on which lifter in which cylinder has collapsed on top of how much it's collapsed.. In my case, I don't know exactly which one it is as I haven't done any tear down yet, but I know it's on 4 or 6. Mine started as a minor tick that dealer said was the HPFP and 'normal'. Then it turned into a squeak/chirp, again dealer said HPFP and 'normal, they are noisy pumps'. Just after power train warranty expired, it turned to a tap and now dealer is saying "something in the motor and may cost approx $4k to fix". I haven't really noticed any rough running, and no misfires are being logged, so my guess is that my lifter is collapsed enough to make noise but is likely still opening the valve enough to let intake in or exhaust out... I'm probably down on total power, but it's been a gradual or minor change so I never really registered a single event when performance dropped.

I'll do the fix myself, and pop a small cam in while I'm at it..

FYI, I tuned DOD out 2 months after purchasing the truck, so it's only run a total of about 3500 miles with DOD enabled... my failure happened years after DOD was disabled via HPTuners, so I can positively say that disabling DOD via tune alone won't fully eliminate the possibility of the system having mechanical failures. The only way to really fix it, is to remove it physically from the engine.