#7 Cylinder Misfire

cpttimerestraint · September 11, 2018

53k miles. Tech said it can happen at any mileage.

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Brandon Lynch · September 13, 2018

I too have 2015 Silverado. I just got my truck back from dealer had a collapsed lifter #7 at 65k. It ran great for two days tell I hit the passing gear it started popping and went back into dealer and I took the Mechanic for a ride and #7 failed again also thinks the vlom is bad so I'm in a loaner for a while I'll post more info as I get it.

Brandon Lynch · September 21, 2018

Ok I got my truck back today the afm lifter on #7 came apart and ended up bending a rod. They replaced the rod, afm lifter this is the third one in less than 100 miles and they replaced the vlom. It seams to be running great right now and I put a range device in so hopefully I won't have anymore problems.

TigerTW0014 · August 1, 2019

On 5/23/2018 at 11:41 AM, Glen Kierstead said:

Had this same thing happen to my 2014 5.3 LT Z71 with less than 37k miles on it. Happened to me yesterday. CEL Flashing with the Stabiltrak light solid. Start ticking even while pressing the gas. Rough idle and just running and sounding like dog crap! Called and scheduled a service appointment on it today for tomorrow at 7am. My code reader just showed P0300. Will update on what I find out over the next few days. Really disappointing tho. Almost want to just fix it and then sell it!!!

Can you update on what the issue was? I'm having exact same symptoms, #7 5.3 '14 112k afm tuned out.

JHall- va · September 23, 2019

09/23/2019:

Similar issue here, recently...P0307 Code/ Engine Light...

Was told by my local GM Dealer - that they would NOT rebuild the engine, and that they would only "replace" the engine with this issue...well over $7,000 to do this!

My #7 plug is "Fouled"...causing the mis-fire and is in fact leaking oil.

Unfortunately, my truck (2014 Suburban) has 86,000 miles on it - and NOT under Powertrain Warranty!

Any advice??

thanks - John

Edited September 23, 2019 by JHall- va

Charlie h · June 4, 2021

Im just staring to have the same problem at my 2017 z71 with 39,865 miles...

Skeeterhawk · June 11, 2021

On 6/4/2021 at 1:04 PM, Charlie h said:

Im just staring to have the same problem at my 2017 z71 with 39,865 miles...

Well my 2017 only had 28,500 miles and had all injectors replaced and didn't fix the problem. Was spitting out P0300 and P050D codes. Dealership just changed all the lifter. They are in test drive mode now. If this fixes the problem I'm selling the truck and getting a Ford. This is the right time to sell anyway. The dealership also told me they are still having lifter problems in 2020 trucks . Bye, Bye GM.

T-Town-Z · July 6, 2021

Here we go again ! 4 years and 85,000 miles ago, I had the #7 lifter fail and had it covered under the power-train warranty. Now I'm at 139,000 and it looks like I have another #7 AFM lifter failure. But get this, I tuned off the AFM at 99K miles, and it still failed !!!

For a couple weeks before, I noticed that when on the highway, if I stepped on it hard and it downshifted, it would do a double backfire sound, kind of a stutter, then finally regain itself and go. I had gotten gas at a station I've never used before and thought it was bad gas. I added a bottle of fuel treatment and finally refueled. Next day, I'm on the highway and go to pass a semi, and when it downshifted, it did the double backfire thing again, but this time I hear a sort of bang in the engine, then it stuttered, then the check engine light comes on, along with traction control light, engine vibration and reduced power. I limped it into work and checked the codes and have P0300 , P0307 & P0324 .

Luckily I live down the street from the guys that own Prevatt Automotive Tuning here in Tulsa. Initial diagnosis is a dead #7 AFM lifter and hopefully nothing worse. Now just waiting for my turn in their shop.

I'll update in a week or so once they open it up......