Surge, RPM Fluctuation, No Codes

[Heathen0042]

2011 Yukon Denali XL 1500 6.2L

Today was a colder and wetter morning than usual in my area. I remote started my truck to let it warm up for a bit before I got into the truck. About 5 minutes later I got in, turned the key and was off on my way. About 1/4 mile in @25 mph, the truck started revving on its own. Short jerky spurts from way below idle up to about 2,500 - 3,000 RPM. I put it in neutral because it was banging the drivetrain pretty good. As I was pulling over it just died. I restarted the truck and it all seemed to go back to normal. No check engine light, no warnings on the dash, no stored codes, so I am at a loss. The only long term symptom the truck has had is a slight rough idle when driving it. Even that is intermittent and typically only noticeable at a full stop. Any thoughts on what to check or troubleshoot would be greatly appreciated.

 

[swathdiver]

2011 Yukon Denali XL 1500 6.2L

Today was a colder and wetter morning than usual in my area. I remote started my truck to let it warm up for a bit before I got into the truck. About 5 minutes later I got in, turned the key and was off on my way. About 1/4 mile in @25 mph, the truck started revving on its own. Short jerky spurts from way below idle up to about 2,500 - 3,000 RPM. I put it in neutral because it was banging the drivetrain pretty good. As I was pulling over it just died. I restarted the truck and it all seemed to go back to normal. No check engine light, no warnings on the dash, no stored codes, so I am at a loss. The only long term symptom the truck has had is a slight rough idle when driving it. Even that is intermittent and typically only noticeable at a full stop. Any thoughts on what to check or troubleshoot would be greatly appreciated.

No codes in the transmission module? No event history? This is electrical or a solenoid problem at first glance. Are you in Ohio? @AirJordan613

 

[Heathen0042]

No codes that my tuner would pick up or event history. Its usually pretty good about logging events and picking up codes. I had to get to work so I didn't have much time to troubleshoot. After work I can try a different scan tool and see if that has any luck.

Florida actually, I should have specified. It was in the 50's this morning and rained all night. Its nothing like what the folks up north have to deal with.

 

[Doubeleive]

first thing you will want to check is battery connections, take the cables off and clean up the post's real good (wire brush or sandpaper) and re-attach
even if the post's look ok do it anyway.
poor electrical connections make these trucks do weird things
also if you haven't done it recently or at all clean the throttle body and maf, new air filter
and throw some injector cleaner in the gas tank for a few tanks fulls, put 2 bottles in per tank, it's .99 cents at walmart
if you are near or above 100k it's time for plugs & wires
if the problem persist's I would move on to monitoring the fuel pressure if that looks ok, might be time to have the transmission looked at.

 

[swathdiver]

No codes that my tuner would pick up or event history. Its usually pretty good about logging events and picking up codes. I had to get to work so I didn't have much time to troubleshoot. After work I can try a different scan tool and see if that has any luck.

Florida actually, I should have specified. It was in the 50's this morning and rained all night. Its nothing like what the folks up north have to deal with.

What do you mean? They have their struggles and we have ours! I had to put up the shorts and flip flops because it is so cold outside! Can't catch any rays because of the cold and rain, even a little foggy out right now still. Should burn off soon.

If you are near me we can put the Tech-2 on it.

 

[Heathen0042]

first thing you will want to check is battery connections, take the cables off and clean up the post's real good (wire brush or sandpaper) and re-attach
even if the post's look ok do it anyway.
poor electrical connections make these trucks do weird things
also if you haven't done it recently or at all clean the throttle body and maf, new air filter
and throw some injector cleaner in the gas tank for a few tanks fulls, put 2 bottles in per tank, it's .99 cents at walmart
if you are near or above 100k it's time for plugs & wires
if the problem persist's I would move on to monitoring the fuel pressure if that looks ok, might be time to have the transmission looked at.

Funny enough, I have done almost all of that about 2 months ago except plug wires. I was doing just some routine maintenance and trying to get rid of the rough idle. Then about a month ago I had to get the transfer case replaced. The bushing for the input shaft went bad leaked all the fluid out. Smoked the T-Case and the yolk. That being said I hope that it isn't a tranny issue because it was already replaced about 50k miles ago.

I will for sure check the battery out again and clean it. Ill check out the MAF and throttle body and see how they are holding up. I did plug wires around 35k ago, but they were the cheap ones and I wouldn't be surprised if they are the culprit.

I do have a fuel pressure gauge so it would be pretty easy for me to see what I am getting on the rail.

Thanks for your suggestions.

 

[Heathen0042]

What do you mean? They have their struggles and we have ours! I had to put up the shorts and flip flops because it is so cold outside! Can't catch any rays because of the cold and rain, even a little foggy out right now still. Should burn off soon.

If you are near me we can put the Tech-2 on it.

Haha! I hear you.

I appreciate the offer, but I am a pretty good haul away from the Treasure Coast area.

 

[swathdiver]

Haha! I hear you.

I appreciate the offer, but I am a pretty good haul away from the Treasure Coast area.

Ok, we've got regulars on here up in Jacksonville, Tampa/St. Pete area, Sugarloaf Mountain, Haines City, and a bunch down south in West Palm, Broward and Dade counties.

 

[Heathen0042]

Update: Truck turned on fine and drove fine for about a mile. I was braking going into a turn lane and the engine just stalled. All accessories were still running fine. No codes, no revving or anything. Will see if i can pull TCM codes.

 

[Heathen0042]

Okay no stalling today. I did clean the throttle plate again. Checked the terminals, looked for shorts, and cleaned the MAF, and got 60 PSI at the rail. I still have plug wires and tuff to check. She is running better. The throttle plate was pretty bad. Which leads me to my second question. Anyone have any idea what the heck this is? The hole its coming from is where a valve/hose connects to the upper intake from the fuel rail/valve cover area on the passenger side.

 

[Doubeleive]

Okay no stalling today. I did clean the throttle plate again. Checked the terminals, looked for shorts, and cleaned the MAF, and got 60 PSI at the rail. I still have plug wires and tuff to check. She is running better. The throttle plate was pretty bad. Which leads me to my second question. Anyone have any idea what the heck this is? The hole its coming from is where a valve/hose connects to the upper intake from the fuel rail/valve cover area on the passenger side.

View attachment 362948View attachment 362949View attachment 362951

milkshake from the pcv, probably need a catch can

 

[Heathen0042]

milkshake from the pcv, probably need a catch can

Would that be a failing PCV that needs to be replaced or does it just need a catch can?

Edit: If this thing even has a PCV valve. I assumed it did because my other truck has one, but I dont see a valve listed online. Just a hose that connects the PCV to the intake.

 

[donjetman]

Which leads me to my second question. Anyone have any idea what the heck this is? The hole its coming from is where a valve/hose connects to the upper intake from the fuel rail/valve cover area on the passenger side.

There is no pcv valve. The pvc system is built into the valve cover.
There is a Technical Service Bulletin that may apply?

https://f01.justanswer.com/ebrock63...il+Consumption,+MIL+ON,+Engine+Runs+Rough.pdf

Vehicles Built Prior to February 1, 2011 Require Updated Valve Cover

Aluminum or Cast Iron Block - Oil in Intake Manifold - Install Updated Valve Cover on All Models Built Prior to February 1, 2011

 

[swathdiver]

Okay no stalling today. I did clean the throttle plate again. Checked the terminals, looked for shorts, and cleaned the MAF, and got 60 PSI at the rail. I still have plug wires and tuff to check. She is running better. The throttle plate was pretty bad. Which leads me to my second question. Anyone have any idea what the heck this is? The hole its coming from is where a valve/hose connects to the upper intake from the fuel rail/valve cover area on the passenger side.

What percent is the throttle plate at while idling? Ideal is around 3-5%. Mine is getting long in tooth and is getting up around 7-9% but my idle has also been raised so that it won't stall if you let off the gas too fast.

 

[Doubeleive]

Would that be a failing PCV that needs to be replaced or does it just need a catch can?

Edit: If this thing even has a PCV valve. I assumed it did because my other truck has one, but I dont see a valve listed online. Just a hose that connects the PCV to the intake.

like noted above it's built into the drivers side valve cover, there is a updated one, but either way a catch can will help prevent the oil +moisture mix from getting into the intake.

 

[Heathen0042]

What percent is the throttle plate at while idling? Ideal is around 3-5%. Mine is getting long in tooth and is getting up around 7-9% but my idle has also been raised so that it won't stall if you let off the gas too fast.

I am still around the 3-5% area.

 

[Heathen0042]

Just an update: After cleaning the throttle plate, the truck hasn't stalled again. I did just have my catch can come in, and plan on installing sometime soon. As of right now I am going to call this issue resolved. Thanks for all of your input guys.