3.6L LLT RPM jumping, engine surging, poor gas milage

57133 Views 48 Replies 27 Participants Last post by Bdaca, 13 d ago

Lbm8664

Discussion Starter · Jun 14, 2018 (Edited by Moderator)

I’ve seen posts similar to this issue I’m experiencing but wanted to throw out my experience. It started with noticing my car feeling like it was jumping slightly while in cruise or sometimes when I’m pressing the Accelerator. I recently noticed my RPM bouncing up and down very noticeable when in cruise or any other time really. Gas Mileage is horrible now as well. Got the oil changed and put fuel injector cleaner and it seemed to act better but soon (a few days of driving) symptoms returned.

Took it to a state park with many steep hills with a speed limit of 15 and at two points when going up the steepest it felt like it was going to choke out and die but I gassed it and it went away. I drive it daily in home health and noticed it getting worse with the engine jerking a couple of days ago it felt like I was driving on a cobblestone road when trying to accelerate onto the highway but after pressing gas harder it stopped. took it to the mechanic not throwing any codes.

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nanookvd

· #41 · Jan 19, 2022

Just changed out the APPS. I disconnected the battery and reconnected it after I was finished. No relearn needed.

After 6 months of symptoms, the vehicle finally put out a P2138 code while my daughter and I were getting some hours in on her driver's permit.

Torque converter shudder, fluctuating RPM, and throttle response lag is gone!

$90 and about 2 hours of work is a much better than a $4,500 transmission swap.....lol

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Genese

· #42 · 8 mo ago

Just bought a 12 Acadia Denali. 145000 Has all the standard misfire symptoms. I replaced all plugs/coils, purge valve. No cell lights. No misfires reporting on scan tool. Scan tool shows bank 1 fuel trim varying degrees of too rich. Seems to misfire ( or tyranny slip) under light load low rpm. It doesn't happen pulling a trailer in trailer mode. I cannot find any definitive proof of timing chain issue and cabt decide if I should go after timing or torque convertor.

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nanookvd

· #43 · 8 mo ago

Genese said:
Just bought a 12 Acadia Denali. 145000 Has all the standard misfire symptoms. I replaced all plugs/coils, purge valve. No cell lights. No misfires reporting on scan tool. Scan tool shows bank 1 fuel trim varying degrees of too rich. Seems to misfire ( or tyranny slip) under light load low rpm. It doesn't happen pulling a trailer in trailer mode. I cannot find any definitive proof of timing chain issue and cabt decide if I should go after timing or torque convertor.

Correct, the transmission in trailer mode runs the engine at higher rpm and shifts at different points to account for the additional load. See below discussion for additional insight. People have gone varying routes with limited success to fix the problem. What is changed, in addition to how the work was done, goes into if/how well/how long the repair lasts.

Jerking/Shuddering Under Light Load - 2nd Gen Acadia

Hello Everyone, New to the forum here, happy to be a part of it! I have a 2017 Acadia Denali with ~133,000 miles. About two months ago I noticed a jerking/shuddering at highway speeds, generally between 50-65mph. This only happens under light acceleration or cruising up a slight incline. If...

www.acadiaforum.net

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dorsett316

· #44 · 5 mo ago

Lbm8664 said:
I’ve seen posts similar to this issue I’m experiencing but wanted to throw out my experience. It started with noticing my car feeling like it was jumping slightly while in cruise or sometimes when I’m pressing the Accelerator. I recently noticed my RPM bouncing up and down very noticeable when in cruise or any other time really. Gas Mileage is horrible now as well. Got the oil changed and put fuel injector cleaner and it seemed to act better but soon (a few days of driving) symptoms returned. Took it to a state park with many steep hills with a speed limit of 15 and at two points when going up the steepest it felt like it was going to choke out and die but I gassed it and it went away. I drive it daily in home health and noticed it getting worse with the engine jerking a couple of days ago it felt like I was driving on a cobblestone road when trying to accelerate onto the highway but after pressing gas harder it stopped. took it to the mechanic not throwing any codes.

I have the same problems, I have been told numerous culprits and non have been proven to be the problem. I was told it was timing going bad, drive shaft warped, wheel barring, coil springs, even and oxygen sensor that we did replace and still no change.i would get rid of it if i could but owe more than it’s worth

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Jon1207

· #45 · 2 mo ago

Hi! I'm totally new to this! But I have a 19 Acadia, that when I hit the accelerator pedal on a stop, turn or green light it has a slight jerk (sorta like a manual transmission but not as aggressive) and I have taking it to the dealership TWICE. They said they can't find the solution or tell me it's possibly the battery, CCA is at 550 needs to be at 770.
I've read all the comments, and all of have been suggested as torque converter, mass air flow etc etc. What I wasn't told was the AAP, vehicle has 80k miles on it now. Not sure what to do, is the AAP hard to do? I don't mind learning new things like this. Cause my warranty runs out in like 12k miles and I'm just stressed out. I already have another car in shop getting the trans replaced (CEL come on). So I'm just lost, any suggestions?? Thank you

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JayTee2019

· #46 · 2 mo ago (Edited)

Jon1207 said:
Hi! I'm totally new to this! But I have a 19 Acadia, that when I hit the accelerator pedal on a stop, turn or green light it has a slight jerk (sorta like a manual transmission but not as aggressive) and I have taking it to the dealership TWICE. They said they can't find the solution or tell me it's possibly the battery, CCA is at 550 needs to be at 770.
I've read all the comments, and all of have been suggested as torque converter, mass air flow etc etc. What I wasn't told was the AAP, vehicle has 80k miles on it now. Not sure what to do, is the AAP hard to do? I don't mind learning new things like this. Cause my warranty runs out in like 12k miles and I'm just stressed out. I already have another car in shop getting the trans replaced (CEL come on). So I'm just lost, any suggestions?? Thank you

Translate for those who do not know - --
AAP . . . . ?

And, yes, a battery that is not up to full State Of Charge can cause all sorts of issues including shifting.
https://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

If a single cell in the battery has an internal intermittent short, for instance, the battery voltage will jump back down to 10.5 or 11.0 volts.
This is enough for the "battery saver" and other programmed operations in the ECM. BCM, TCM, to cause fail safe modes to occur.
We just had our battery do essentially this on our 2019 SLT and I thought it was just an anomaly and ignored it.
Two days later the Acadia would not start and posted a low battery voltage message.
All sorts of lights cam on and even after a jump stat. . . . they were not cleared until the battery was replaced the next day.

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Bdaca

· #47 · 13 d ago

Lbm8664 said:
I’ve seen posts similar to this issue I’m experiencing but wanted to throw out my experience. It started with noticing my car feeling like it was jumping slightly while in cruise or sometimes when I’m pressing the Accelerator. I recently noticed my RPM bouncing up and down very noticeable when in cruise or any other time really. Gas Mileage is horrible now as well. Got the oil changed and put fuel injector cleaner and it seemed to act better but soon (a few days of driving) symptoms returned.

Took it to a state park with many steep hills with a speed limit of 15 and at two points when going up the steepest it felt like it was going to choke out and die but I gassed it and it went away. I drive it daily in home health and noticed it getting worse with the engine jerking a couple of days ago it felt like I was driving on a cobblestone road when trying to accelerate onto the highway but after pressing gas harder it stopped. took it to the mechanic not throwing any codes.

I had the exact same problem. Engine rpm jumping in and out around 400 rpm cruising. Did it in alls gears and overdrive..torque lock. Read all the forums and appears this is a common problem with no real solutions and lots of money later. I was able to fix my issue finally. The rubber boots coming off the air box has 2 clamps with the other side glued from factory. The glue gave out about 1/4 inch on the bottom. It was enough of a leak to let air suck in post maf/map sensor. No codes were ever present. I put a clamp on...drove it and all surging the past 2 years disappeared. Hope thos helps.

Lbm8664 said:
I’ve seen posts similar to this issue I’m experiencing but wanted to throw out my experience. It started with noticing my car feeling like it was jumping slightly while in cruise or sometimes when I’m pressing the Accelerator. I recently noticed my RPM bouncing up and down very noticeable when in cruise or any other time really. Gas Mileage is horrible now as well. Got the oil changed and put fuel injector cleaner and it seemed to act better but soon (a few days of driving) symptoms returned.

Took it to a state park with many steep hills with a speed limit of 15 and at two points when going up the steepest it felt like it was going to choke out and die but I gassed it and it went away. I drive it daily in home health and noticed it getting worse with the engine jerking a couple of days ago it felt like I was driving on a cobblestone road when trying to accelerate onto the highway but after pressing gas harder it stopped. took it to the mechanic not throwing any codes.

SEE IF THE BOOT FROM THE AIR BOX HAS UNGLUED. PUT A HOSE CLAMP ON IT.

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Jon1207

· #48 · 13 d ago

Gonna have to check that out tomorrow, now when you said air box. Do you mean the one the engine air filter seats in? What area is the boot located at?
I've taking it to the dealership 4 times by now and still nothing. Did a transmission flush, seemed to sorta work. Less frequent jumps but eventually came back, at this point they are tired of me and vice versa lol. They think it's me pressing the pedal to hard, or could be the fluid swooshing around (which i find kind of ridiculous). Even got a case with GMC but since I stopped taking it they stopped the case. Told myself just gonna have to figure this **** out myself. But anyway sorry for the rant it's just so frustrating especially since i bought this car may 2022 at 57k miles! Gonna check the box tomorrow and see if that works.

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Bdaca

· #49 · 13 d ago

Jon1207 said:
Gonna have to check that out tomorrow, now when you said air box. Do you mean the one the engine air filter seats in? What area is the boot located at?
I've taking it to the dealership 4 times by now and still nothing. Did a transmission flush, seemed to sorta work. Less frequent jumps but eventually came back, at this point they are tired of me and vice versa lol. They think it's me pressing the pedal to hard, or could be the fluid swooshing around (which i find kind of ridiculous). Even got a case with GMC but since I stopped taking it they stopped the case. Told myself just gonna have to figure this **** out myself. But anyway sorry for the rant it's just so frustrating especially since i bought this car may 2022 at 57k miles! Gonna check the box tomorrow and see if that works.

Yes check the air intake tube boots. The factory glued the boot ends to the hard plastic tube and you have the hose clamps on the other end with 1 going to air filter box and other to intake body. The boot had came unglued only a 1/4 inch. Enough to hear a vacuum hiss sound. This is post maf sensor. I Put hose clamps on the boots, started the car and took it on a drive. The surging was very minimal, almost unnoticeable the first 3 miles, then went completely gone. That was my $2 fix The acadia never showed codes for some reason. My surging issue happened in all gears...and really felt it on the freeway in torque lock. On freeway you can watch rpms jump and feel the pull. Only other thing I did was change tranny fluid since had 120000 on it. Read many forums with what sounded the exact same issue I had. No way was I going to change torque convertor, coils, injectors, etc. No one seemed to have a fix. Maybe the acadia has other issues as well but mine was simple and hope this helps others to check before they get knee deep in part swaps.

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