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It was my friend’s scanner…he says it was supposed to pick up tranny codes, but I’m not 100% sure. All I can say is that I have no codes or pending codes. I’m beginning to think new coil packs are a long shot, but it is possible to have a misfire and not throw any codes, but from the way this shudder feels, I would think the computer would pick it up if it were a misfire…

The shudder was more severe after I’d been driving several hours already…I couldn’t make it do it today…
 

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No CEL on my D in L 'nox with the trans. issues BTW.
 

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Sounds like TC issues or some other related transmission issues alright.
Any shudder issues should be looked at very soon as debris can build up and take out more parts in the process.
 

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With my harbor freight scanner, i can go into the selection and see the number of misfires.
Even if it didnt set the cell.
Usually do this when I feel a little stumble.....
I scan, and can see a cylinder with maybe 15 misfires.
Low numbers usually.
 

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…I’m beginning to lean towards TC too…I’m going to try a couple of tubes of Lubegard Shudder Fixx as a diagnostic. It gets amazing reviews and if it makes the problem better, I’ll know I’ve got a Torque Converter issue…
 

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@BandDirector : but is your Scanner going to pick up Transmission Codes? I thought you needed a “professional” Scanner to be able to do that ... either at the Dealer, or an Independent with one of those (more sophisticated) SnapOn units...
Colt P0700 is one of the more famous trans. codes. There a few trans. codes in the P family.
 

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Just put in 2 tubes of Shudder Fixx and went on a test drive. Seems better, but I really won’t know for sure until my next trip soon…new coil packs arrive today, but I think I’ll wait to install them. If it’s truly a misfire, it’ll eventually throw a code I would think, so I’ll just see how the Shudder Fixx does for now…
GM threw a minor wrench in my plan on Monday when they announced another price increase on the C8 by $2300…
 

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Colt P0700 is one of the more famous trans. codes. There a few trans. codes in the P family.
Actually, now you've reminded me that I once got a P1744 Code with my 1997 Ford Taurus Wagon for "Excessive Torque Converter Clutch Slippage Detected" ... something like that. It was right after I had totally transfused all the Fluid (after almost everyone on the Taurus Car Club Forum had told me not to do it since I had over 100,000 miles and this was my first Fluid change!). LOL!

@BandDirector : that's the thing with those ultra-high-priced vehicles ... everybody just assumes "you've got it", so they think nothing of whacking you any chance they get. I remember my sister-in-law buying her Mercedes Convertible (hard top/soft top) right after her husband killed himself ... then being mortified by her first repair bill: $800 "tune-up"! And this was back in the early 90's! I told her ... "they saw you coming from a mile away ... everything suddenly becomes more expensive when you project an image that says ... 'hey - money's no problem for me!'...
 

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I had converter lock up codes in my old '00 Sable wagon. At 220 miles I sold it as it as changing the solenoid was a PITA the car wasn't worth. Just highway mileage suffered.
 
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Discussion Starter · #70 ·
My past experience with GM transmissions:
- Slipping - flat out loss of power delivery, your body will move forward at the loss of power delivery, the tach will jump, and then usually you can see and feel when things engage correctly finally.
- Shudder - we had wave plate failure on the 5-6 clutch on our 2008 Nox Sport, there was no power delivery issues, but it felt like we were running over a rumble strip during that shift
- Mis-fire - Our 2015 Terrain had this which is what started this thread initially. It is more of a stumble, a single mis-fire just feels like a little thump in power delivery, the tach doesn’t really move any since the engine and transmission should be in gear with the TC locked. Of course sitting at idle or if the TC hasn’t locked yet, it might feel a bit different. Most of our mis-fires were at cruising speed.
 

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My past experience with GM transmissions:
  • Slipping - flat out loss of power delivery, your body will move forward at the loss of power delivery, the tach will jump, and then usually you can see and feel when things engage correctly finally.
  • Shudder - we had wave plate failure on the 5-6 clutch on our 2008 Nox Sport, there was no power delivery issues, but it felt like we were running over a rumble strip during that shift
  • Mis-fire - Our 2015 Terrain had this which is what started this thread initially. It is more of a stumble, a single mis-fire just feels like a little thump in power delivery, the tach doesn’t really move any since the engine and transmission should be in gear with the TC locked. Of course sitting at idle or if the TC hasn’t locked yet, it might feel a bit different. Most of our mis-fires were at cruising speed.
But did those misfires eventually set a code?
 

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Discussion Starter · #72 ·
But did those misfires eventually set a code?
Truthfully…I don’t remember. I don’t think it did. We just kept having stumbling from time to time and figured plugs were a safe bet to start with. Pretty sure our only CEL we have ever had on this car was for a failed O2 sensor a while back.


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You will always see some sort of misfires in the counter. CEL will set if X number of misfires occur, not sure on the amount but it calculates misfires per revolution. I think the random misfires in the counter occurs on startups so there are always some in the total count. Happens on a perfectly fine engine.
Misting the coils with water can help detect a bad one.
 

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Discussion Starter · #74 ·
Truthfully…I don’t remember. I don’t think it did.
I lied, I just went back and read the first page of this post. It did pop a CEL a couple of times, but I don't remember any details of what codes were set. If I am thinking of the correct time, we had some stumbles at a stop light, CEL flashed a few times, stumbles kept up, CEL popped, then things went back to normal. CEL didn't stick around after a restart.

Do NOT trust my memory here on any of these exact details other than I did NOT have a long-term CEL. That is the only thing I for sure remember. ;)
 

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Just did 325 miles straight. Shudder Fixx didn’t solve my problem. BUT I finally did something that triggered a flashing engine light…but not for long. There was a member of the “Anti-Destination League” doing 65 in a 70 in the left lane. After riding his bumper for a bit and he still wouldn’t get over, I nailed it to get around him in the middle lane. As soon as I nailed it, I got a flashing engine light as well as traction control light came on. The traction control light went off fairly quickly, but the flashing engine light didn’t go off for 20-30 seconds.
…it also triggered a memory that a couple of months ago, I’d just gassed up, and less than a mile after I left the station, my traction control system went haywire putting on my brakes and even caused my steering wheel to jerk to the right too…I got to the nearest parking lot with it, cut it off and restarted and all was well. That was an awfully odd glitch!
Got me to thinking, is it possible for a bad ABS sensor, or wheel sensor, or whatever sensor we have on our fronts to cause the shudder I’m feeling?
It could still be the coils, or even the torque converter, but I’m still not sure what’s going on.
I’ll change the coil packs this week and see where I’m at after that…
 

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There was a member of the “Anti-Destination League” doing 65 in a 70 in the left lane. After riding his bumper for a bit and he still wouldn’t get over, I nailed it to get around him in the middle lane.
:ROFLMAO:

As soon as I nailed it, I got a flashing engine light ... the flashing engine light didn’t go off for 20-30 seconds.
I've seen this happen on rare occasion with my 2011, too. Never saw a code for it, though ...

…it also triggered a memory that a couple of months ago, I’d just gassed up, and less than a mile after I left the station, my traction control system went haywire putting on my brakes and even caused my steering wheel to jerk to the right too…I got to the nearest parking lot with it, cut it off and restarted and all was well. That was an awfully odd glitch!
Probably a glitchy Wheel Speed Sensor. Mine does that in the parking lot or taking off from a recent startup. I just tap the brake pedal a few times to get it to stop. I need to replace a front Hub, which has a broken Encoder Ring that the Sensor reads. Haven't gotten around to it ...

Got me to thinking, is it possible for a bad ABS sensor, or wheel sensor, or whatever sensor we have on our fronts to cause the shudder I’m feeling?
I've never noticed the ABS thing happening at high speeds with my 2011 ... only at very low speed, and only for a very short period of time, but I guess when something's malfunctioning ... anything's possible ...
 

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Discussion Starter · #77 ·
Got me to thinking, is it possible for a bad ABS sensor, or wheel sensor, or whatever sensor we have on our fronts to cause the shudder I’m feeling?
I guess it is possible, but you never mentioned nor saw the ABS light before. Traction control won’t trigger without the warning lights blinking. You also should hear the ABS pump triggering. Right? Maybe?

I’m actually kind of hoping that is what it is for you since it most likely cheaper than a transmission.


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Ima do coils next, they’re already here, and then the wheel sensors aren’t that much at RockAuto, so I may try those next. Without a code being thrown, I’m shooting in the dark…

TQ converters aren’t but $300-$400, but it’ll sure be a pain to change…

Something is definitely not right, and I’m a pretty good shade tree mechanic, but this is giving me fits…
 

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Just pulled codes. I have a misfire code pending on cylinder #5. I’m worried since that’s the cylinder that has the stripped spark plug…maybe it’s a coincidence and the coil will not show signs of the spark plug blowing out. Praying it’s just the coil and I can replace it to fix my problem…I’ll know soon…
 

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No external damage on coil 5, so I’m thinking the spark plug might not be about to blow out. Computer is telling me it’s #5.

…just thinking out loud again, is there a possibility that the spark plug hole was damaged due to a faulty coil…could that have caused the plug to have welded itself to the threads which is why it stripped when I pulled it out? 🤔

I’m going to replace all 6 coils anyway…
 
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