Stumble/Hesitation AND stalling continuation thread

[bdbull]

Starting a new thread since the thread I started the conversation in was marked as solved.

I have a rough idle on my '10 Avalanche as well. Been battling it for a long time now with no resolution. No codes, no stalls, but it sure feels like it's just a smidge from stalling when I'm sitting at a light. I've also experienced an issue that I think might be the same as your "spike in RPM when coming to a stop." There have been times when coming to a stop, right before finally stopping, where it seems like the truck tries to accelerate instead of decelerate. I haven't actually noticed the RPM's when it happens, but it makes sense. I do know it scared the ever living snot out of my teenager as he's learning to drive.

Think I'm gonna look into swapping out the fuel pump and cross my fingers that will fix it. I've got 210k miles and as far as I know, the fuel pump is original to the truck.

btw, here is a video of my RPM gauge I took yesterday while sitting at a light. You can see it jumping around as I just sit there.

 

[bdbull]

Just finished testing fuel pressure with an actual pressure gauge. Idle pressure stayed right on 46 the entire time. Even as the truck stuttered, the pressure didn't budge at all. Dead on the whole time.

I did notice something strange though. I was doing this test at night, and I had my door open as I was watching the gauge through the windshield. When it would stutter bad, the dome lights would slightly dim. It wasn't a lot, but it was enough to notice. Could this stem from some sort of electrical issue or is that what will happen if the truck actually stalls out?

Also, before I did the test, I checked all my plug wires. One of them did seem loose so I pulled it off and reseated it til I heard and felt the click. It came off pretty easily so it could have very well could have been loose. However, it didn't seem to have any effect on the stutter since it still did it after I reseated the boot.

One more thing I want to mention. I did pull the throttle body this past weekend and clean it. It really wasn't that dirty at all.

 

[Doubeleive]

if the fuel pressure is good I would move on to other possible causes, maf, throttle body, injectors, coil packs.
but start with the basics, battery, battery cables, grounds
you could do a injector service or just keep putting in injector cleaner in for a few tank fulls, clean the maf and throttle body, plugs & wires.
could be several things, narrowing it down may be difficult.

 

[OR VietVet]

How old are the ignition components? Like @Doubeleive said, clean the MAF and since you pulled the throttle body, was it to fix this problem or the problem started after? Cleaners and instructions at parts store and watch you tube videos. Check this link out: https://www.fixmyoldride.com/Chevro...e7e5cd24ed24635&at_ab=per-2&at_pos=3&at_tot=4

Did you have any grounds undone when removed the throttle body. Seems that there is on ground area at back of block, I think passenger side, that is a source of problems at times.

 

[Geotrash]

The lights dimming could stem from the RPMs dropping enough for the alternator's output to drop. Or, it could signal another problem such as a bad ground. As Wes says, check the integrity of this battery cables and clean all of the grounds in the engine compartment. It's a 30 minute job and solves many gremlin-like issues.

 

[bdbull]

The lights dimming could stem from the RPMs dropping enough for the alternator's output to drop. Or, it could signal another problem such as a bad ground. As Wes says, check the integrity of this battery cables and clean all of the grounds in the engine compartment. It's a 30 minute job and solves many gremlin-like issues.

Is there a sticky with all of the grounds to check? Even though I might sound like I know what I'm doing, I'm just a Youtube mechanic...meaning I only know what I have learned from these forums and Youtube.

 

[OR VietVet]

2010 Yukon XL Grounds

Curious if anyone knows where all the Grounds are located? any diagrams or pictures would be great.

www.tahoeyukonforum.com

 

[swathdiver]

Starting a new thread since the thread I started the conversation in was marked as solved.

I have a rough idle on my '10 Avalanche as well. Been battling it for a long time now with no resolution. No codes, no stalls, but it sure feels like it's just a smidge from stalling when I'm sitting at a light. I've also experienced an issue that I think might be the same as your "spike in RPM when coming to a stop." There have been times when coming to a stop, right before finally stopping, where it seems like the truck tries to accelerate instead of decelerate. I haven't actually noticed the RPM's when it happens, but it makes sense. I do know it scared the ever living snot out of my teenager as he's learning to drive.

Think I'm gonna look into swapping out the fuel pump and cross my fingers that will fix it. I've got 210k miles and as far as I know, the fuel pump is original to the truck.

btw, here is a video of my RPM gauge I took yesterday while sitting at a light. You can see it jumping around as I just sit there.

RPMs coming up some right before you stop is the transmission shifting into 1st. BlackBear raises our idle RPMs as a matter of course when he tunes an engine because some motors have a tendency to stall or are close to it. GM of course dropped the idle to bare minimum to please uncle sam. They did this to my 2006 Montana too, it idled way low and often seemed like it was about to stall but never did. Never noticed it with the Yukon.

 

[bdbull]

I've checked a couple of the easier to reach grounds and they all seem fine. The worst one had some dust on it. No rust, no corrosion, no nothing, and all tightened down well.

Unfortunately I had an unexpected hospital stay and am not supposed to do any strenuous activity for quite a while. So not sure when I'll get back to running this thing down. I did throw a bottle of fuel injector cleaner in with my last fill up just to try something.

But it still idles like a coughing dog. Maybe it's meant to idle that low, but it's just so damn annoying.

 

[jeremiahm]

I have been fighting issues for several weeks with clunks, shifts, stalls, CEL's for crank and cam sensors (both new), hard stumble at stops (similar to yours). I finally traced it down to the wire bundle going to cam sensor and on to crank sensor. It was run between the PS lines and was chafing on the metal. Crank sensor was starting to ground out on the PS hard line! I temped it with electrical tape and runs perfect now. Now to the point:

I have always the hard stumble at stops and as part of trying to figure out this issue I put a bottle of LubeGard Transmission Protectant (10oz bottle) based on other posts. Made a huge difference. Seems part of the stumble is low RPM, but the bigger potential issue is torque converter shutter which the LubeGard helps. I saw a huge difference, stops are pretty easy now, still a bit of shutter/stumble, but not much.

My 2 cents, and doesn't count as "strenuous activity". Hope it helps.

Jeremiah

 

[jeremiahm]

I just replaced my fuel pump last month as well with not affect on this.

 

[bdbull]

I have always the hard stumble at stops and as part of trying to figure out this issue I put a bottle of LubeGard Transmission Protectant (10oz bottle) based on other posts. Made a huge difference. Seems part of the stumble is low RPM, but the bigger potential issue is torque converter shutter which the LubeGard helps. I saw a huge difference, stops are pretty easy now, still a bit of shutter/stumble, but not much.

My 2 cents, and doesn't count as "strenuous activity". Hope it helps.

So you put the entire 10oz. bottle in? I was thinking of doing an ATF fluid exchange on my truck anyway, so I may throw this in with it.

 

[Foggy]

So you put the entire 10oz. bottle in? I was thinking of doing an ATF fluid exchange on my truck anyway, so I may throw this in with it.

Yes.. The whole bottle of Red LubeGard or the Silver/Plat bottle...
IMO a fluid "exchange" is worthless and can cause more harm than good - unless
you drop the pan and change the filter FIRST.. Clean pan, pan magnet and everything you can
get to.. FIRST or Only

 

[bdbull]

IMO a fluid "exchange" is worthless and can cause more harm than good - unless
you drop the pan and change the filter FIRST.. Clean pan, pan magnet and everything you can
get to.. FIRST or Only

I dropped the pan and did all that about 15k miles ago. I may skip the exchange and just throw the LubeGuard in and see what happens.

I've actually just noticed some transmission issues lately. When cruising at about 40 in sixth gear, it seems like it can't figure out if it should downshift or not. I've never cared for this six speed compared to the four speed I had in my '03 Avalanche. It just never felt right.

 

[Charlie207]

I dropped the pan and did all that about 15k miles ago. I may skip the exchange and just throw the LubeGuard in and see what happens.

I've actually just noticed some transmission issues lately. When cruising at about 40 in sixth gear, it seems like it can't figure out if it should downshift or not. I've never cared for this six speed compared to the four speed I had in my '03 Avalanche. It just never felt right.

Are you still running with the AFM active? When you're cruising in 6th gear @ 40mph it may be in V4 mode, and when you try to give it some throttle the ECU is fumbling with whether it should downshift while still using four cylinders, or activating all eight cylinders to provide adequate cruising power.

I saw a "hack" a when I first got my Yukon where you can run the truck in Manual Mode - Gear 5, and it would disable the AFM. Try that and see if you stay in V8 mode. I've since gotten a BlackBear tune and had the AFM electronically deleted.

 

[bdbull]

Are you still running with the AFM active? When you're cruising in 6th gear @ 40mph it may be in V4 mode, and when you try to give it some throttle the ECU is fumbling with whether it should downshift while still using four cylinders, or activating all eight cylinders to provide adequate cruising power.

I saw a "hack" a when I first got my Yukon where you can run the truck in Manual Mode - Gear 5, and it would disable the AFM. Try that and see if you stay in V8 mode. I've since gotten a BlackBear tune and had the AFM electronically deleted.

I saw someone else mention this a few days ago so I've been driving with the DIC on that display to see if/when it goes to V4. Honestly, it very rarely ever does it. I've noticed it a few times when coasting downhill, but that's about it.

For the hack, do you mean put it in Manual - Gear 5 and leave it there while driving around? Or do you mean put it in Manual - Gear 5 ONLY when I'm up at cruising speed to keep it from going to 6th? I really only do city driving so I rarely get up over 60MPH so not sure how much the AFM kicks in for me.

 

[Charlie207]

I saw someone else mention this a few days ago so I've been driving with the DIC on that display to see if/when it goes to V4. Honestly, it very rarely ever does it. I've noticed it a few times when coasting downhill, but that's about it.

For the hack, do you mean put it in Manual - Gear 5 and leave it there while driving around? Or do you mean put it in Manual - Gear 5 ONLY when I'm up at cruising speed to keep it from going to 6th? I really only do city driving so I rarely get up over 60MPH so not sure how much the AFM kicks in for me.

Start your car, put it in Manual mode, select Gear 5, and leave it there.

Cycle through your dash info display, and observe INSTANT MPG, and it'll show drive mode: V4 or V8.

There are several YouTube videos showing it in effect.

 

[Charlie207]

Let us know how it works for you.

I've mentioned this procedure three or four times over the last six months, and no one ever reports back.

 

[bdbull]

Let us know how it works for you.

I've mentioned this procedure three or four times over the last six months, and no one ever reports back.

I'll give this a shot when I head out this afternoon. Although I'm pretty sure it's the transmission now. I've been watching the DIC the last couple of days and it very rarely goes into V4 mode. In fact, I made a trip all the way across town and back, about 30 miles, and I never saw it hit V4 once.

I did put the bottle of LubeGuard in last night so we'll see if that has any effect on it. I just put a transmission in my wife's '15 Tahoe so it's only fitting that mine would start to go out now as well. As my dad used to say to me when I was young, "I'll just go out back and pick some more money off the money tree."

 

[Mad-Max]

We are having this exact issue with a 2013 Yukon XL Denali (6.2) we're looking at - currently have it on a 24hr test drive. I'm very interested in any follow-up thoughts about the root cause.
- Sam