Help identify an issue - Skipping/Shaking

[Ozer]

Fixed! See page 2 update. Rebuilt Trans!

 

2014 Sierra 1500 5.3 120k miles 

Hey all,

I searched and read some of the transmission threads but it wasn't helpful so hoping someone can guide me or had the same issue..

 

Truck has been running great no issues, one morning i go to work as usual and half way into the commute i get this skipping/shudder when under load.

I let off it goes away. RPM is steady at idle and its not doing it or is not noticeable in cruise. No codes. Does it in Manual, all gears and all speeds. Only when i get on the gas.

Power is less, it feels like a slipping trans but also feels like a misfire. Plugs are assumed to be originals so tonight im replacing all to see if it fixes it, if not: they needed to be done anyways so no harm done.

Trans has been flushed at 95k at GM dealer. My next option is another flush. Any ideas?

Edited June 5, 2019 by Ozer

[1SLOW1500]

I would not default to coils based on what you stated. 

I would have all history pulled.not all codes show

through a light on dash. 

I lean to debris, trans, or axle. 

Year make and trans? 

Was it ever cleaned out?

If you are throwing a few bucks at it to fix what you think or hope is the issue plugs and wires are cheaper and even though the plugs are good for extended mileage at the price point and 100k miles I would just do it.

[Ozer]

4 hours ago, 1SLOW1500 said:

I would not default to coils based on what you stated. 

I would have all history pulled.not all codes show

through a light on dash. 

I lean to debris, trans, or axle. 

Year make and trans? 

Was it ever cleaned out?

If you are throwing a few bucks at it to fix what you think or hope is the issue plugs and wires are cheaper and even though the plugs are good for extended mileage at the price point and 100k miles I would just do it.

Its the 6 speed 2014.

I have a code reader but not showing anything, whats the best way to pull history codes?

When you say cleaned out, you mean the trans?

[1SLOW1500]

Its the 6 speed 2014.
I have a code reader but not showing anything, whats the best way to pull history codes?
When you say cleaned out, you mean the trans?

My dealer can pull all the history and stored codes. It is amazing what it shows.
Cleaned out the intake manifold and the intake, or the heads. If so with fluid or blast.


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[Ozer]

19 minutes ago, 1SLOW1500 said:

My dealer can pull all the history and stored codes. It is amazing what it shows.
Cleaned out the intake manifold and the intake, or the heads. If so with fluid or blast.


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I bought the truck at 82k miles and at 95k i got the induction cleaning done, trans flush and reared fluid changed at dealer.

I'll post an update tomorrow, after i change the plugs tonight. I been meaning to change them soon anyways.

[Ozer]

Fixed!!     Well, still doingit but new plugs helped a bit.

 

I put in all new plugs, started from passenger side, took the wheel and liner out. Pretty easy that way. Driver side back plug by the firewall was the last one I changed. When I went to pull the spark plug wire, it just fell out from the coil. There was green corrosion. Cleaned all that out and put everything back together. Went for a test drive and it was back to normal. 

Glad it was an easy fix. I probably should have checked the fit on all wires before doing anything, since I assumed it was a misfire. 

 

Also, the electrodes were worn down compared to the new ones. This is at 120k miles. They all looked worn down. 

Edited May 17, 2019 by Ozer

[1SLOW1500]

this is why I said to start with wires and plugs. ACdelco performance wires are only $40 from Amazon and then I pack the connection with dielectric grease. They have a very strong firm click on. I have used these wires on builds over 1000rwhp. 

Happy to see you got it and it wasn't expensive.

[Ozer]

11 hours ago, 1SLOW1500 said:

this is why I said to start with wires and plugs. ACdelco performance wires are only $40 from Amazon and then I pack the connection with dielectric grease. They have a very strong firm click on. I have used these wires on builds over 1000rwhp. 

Happy to see you got it and it wasn't expensive.

Ok 85% better but still hickups here and there under light load.

Im going to take that coil out and see. Maybe even just put a new coil on that cylinder. In wide open it doesnt do it or i cant tell it does.

[1SLOW1500]

Need to run a scan as it is driven see the load at rpm vs o2 and fuel pulse. I wonder if you have a bad injector. More common then you think.

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[Ozer]

7 minutes ago, 1SLOW1500 said:

Need to run a scan as it is driven see the load at rpm vs o2 and fuel pulse. I wonder if you have a bad injector. More common then you think.

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Do injector cleaners in fuel do anything? It may be an inexpensive try to see if it does anything, IF the injector is clogged that is vs not working properly.

[1SLOW1500]

I don't think they do but for the cheap price it is worth the try. Hand held higher end scanners can pulse them and see the pulse in the tool. Also you can see the 02 levels in that bank. As there isn't individual control per cylinder that bank would all show a issue and commanded afr would be adjusted.

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[1SLOW1500]

Injectors are relatively inexpensive but you must also replace 2 fuel lines and it is all under the intake manifold. So a head intake blast is recommended at that time.
If you do or have that done I would also clean the maf and intake and the 4 o2 sensors at that time as it is just a few minutes worth of time.

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[Ozer]

 

On 5/16/2019 at 9:43 AM, 1SLOW1500 said:

Injectors are relatively inexpensive but you must also replace 2 fuel lines and it is all under the intake manifold. So a head intake blast is recommended at that time.
If you do or have that done I would also clean the maf and intake and the 4 o2 sensors at that time as it is just a few minutes worth of time.

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Update:

 

So i have put in new plugs then new wires and last night all new coils and i still get misfires, 1 or 2 random ones in few cylinders but number 3 stands out with 20+ misfires per cycle.

Used a bottle of injector cleaner but not sure of that did anything. 

Whats my next steps, take it to dealer fir further investigation? No codes show up for me. I use Torque Pro to monitor data.

[L86 All Terrain]

12 minutes ago, Ozer said:

 

Update:

 

So i have put in new plugs then new wires and last night all new coils and i still get misfires, 1 or 2 random ones in few cylinders but number 3 stands out with 20+ misfires per cycle.

Used a bottle of injector cleaner but not sure of that did anything. 

Whats my next steps, take it to dealer fir further investigation? No codes show up for me. I use Torque Pro to monitor data.

You didn't know where the miss was before but now you know it is Cylinder 3? Like it shows up as Cyl3 misfire on a scan tool? You probably just got a bad plug or wire in your new set. This has happened to me twice on truck engine spark plugs. Bad plug out of the box, and back to Napa I go. Now I buy 9 plugs when I do them, throw 1 in the glove box if they all work. An easy thing to do is switch your plug wire from cylinder 3 and 5, see if the miss goes to #5, if it does get 1 new wire, if nothing changes change plug #3. Also, did you gap your spark plugs to 0.037 - 0.043? 

Edited May 23, 2019 by L86 All Terrain

[Ozer]

2 minutes ago, L86 All Terrain said:

You didn't know where the miss was before but now you know it is Cylinder 3? Like it shows up as Cyl3 misfire on a scan tool? You probably just got a bad plug or wire in your new set. This has happened to me twice on truck engine spark plugs. Bad plug out of the box, and back to Napa I go. Now I buy 9 plugs when I do them, throw 1 in the glove box if they all work. An easy thing to do is switch your plug wire from cylinder 3 and 5, see if the miss goes to #5, if it does get 1 new wire, if nothing changes change plug #3. 

# 3 was part of the group that was misfiring before the plugs and wires but thats an easy thing i can try and see if it changes.

If not, it the injector could be the issue. 

Anything else that can cause a misfire?