2014 Sierra 5.3L Misfire Cylinder 1 then Cylinder 5

centx_engr · November 30, 2017

I just wanted to share my experience here with anyone so they can follow along and maybe it will help them gather information on any problems. I have approximately 50K miles on my 2014 Sierra CC Z71. It was trouble free up until this point and I was very pleased with my truck's appearance, interior, and capabilities.

At about 48K miles, the first CEL problem hit. I bought a boat which weighs about 4K pounds and I tow it around Austin TX to get to Lake Travis or Lake Austin. The day after an outing as I'm driving to work I notice very hard down shifting when slowing down to a stop. A couple of days later, the problem went away. I chalked it up to the engine control unit trying to learn my new driving habits since it hadn't towed prior to this.

A few weeks later my wife was driving the truck and reported that the CEL light and TCS light came on and the truck was violently shaking. I take off lunch to go meet her in a parking lot and cannot reproduce the problem. I search and surmise that the problem was a misfire.

A week later when starting up the truck on the return leg of a trip between Austin and San Antonio, the same thing happens (CEL + TCS = Misfire). Shut off engine and wait 10 minutes, problem goes away. Definitely a misfire.

Two weeks later, and the problem comes back and is repeatable. I have it towed to a local dealership and they surmise it is a fuel injector problem. Since I'm outside of the bumper to bumper warranty this fix is on me and costs $950 to do one bank. They said that all 4 injectors have to be replaced in order to warranty this fix.

Get the truck back. Running good. One week later, CEL light and TCS light come on with violent shake (misfiring repeatedly and hard). Take it in and to their credit, they replace Coil #5 for free, pay for the tow, and they get it done fast. (Note: both times they gave me a loaner truck so it was okay. The first time, they thought that it was a loose spark plug wire so I didn't get the loaner truck right off the bat, but when they pulled it up front at the service department the misfire was reproduced and they immediately gave me a loaner on the spot and apologized).

I'm starting this thread because I'm kind of worried that the truck is trying to hide its real problem from the techs and that it is the AFM lifters and camshaft.

If this final fix clears it up, I will definitely update the thread so that others can have some confidence if they find themselves in the same spot. If it comes back, I'll update as well.

Fingers crossed that this is it.