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2018 Sierra Denali
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755 Posts
Discussion Starter · #1 ·
So the the truck is a 2013 1500 with the 5.3. It has long tube headers and a whipple supercharger on 8 pounds the truck was dyno tuned and ran great for about a year.

Recently it will backfire about 4 or 5 times in a row and you can feel the truck stumbling. It only seems to do it when I accelerate enough to get the truck to downshift. If i back off the throttle it will stop as soon as I do but if i continue it will continue to stumble backfire half a dozen times or so then it will take off and drive normal. Just after it does this the check engine light will flash a couple times then turn off. Other than that it runs fine and there are no idle or starting issues at all.

my handheld won't read the code because the light turns off.

Also one day I revved the truck when it was parked and stood near the exhaust, when I did so I could see some black smoke coming from the exhaust, not a ton or a huge cloud but enough of a hazing where I could see it.

The air filter is clean and I didn't have a ton of time the other day so I pulled one plug out, the one i pulled looked fine but I didn't have enough time to check them all.

Any comments or ideas are welcome and thanks in advance
 

· Super Moderator, How-To Author, TOTM
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5,109 Posts
A flashing light could mean misfire. I know my truck ran rich and had black smoke upon start up. No black otherwise noted, but the tail pipe tip would get black often and would need to be cleaned. Since the tune was leaned up a bit, I haven't had to clean the pipe tip for quite some time now. I notice cleaner starts too.
 

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I have not had a forced induction GM vehicle, however had a 2006 supercharged hemi charger for a couple years. Part throttle boost is a killer on those engines. Maybe scope the cylinders to make sure nothing cracked or chipped. The top ring land may work harden and crack. Also, work with your tuner, sometimes the tunes adapt and adjust fuel, not realizing it is forced induction. Good luck.
 

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2018 Sierra Denali
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755 Posts
Discussion Starter · #4 ·
The truck doesn't get used much however has had absolutely no problems till now I was almost leaning toward plugs and wires. Would like to get the saved engine code read to see what it was but I don't have any easy access to one minus a garage or dealer. I was thinking misfire with the way it is acting hence the thought about plugs and wires. I may try to find somewhere this week that can plug in for cheap or free and just see if there is a stored code in there.

The supercharger has a bunch of miles and almost a full year of being installed with no issues so I wouldn't think that it would be in the tune but anything could happen I guess.

Thanks for the responses, hopefully this is a relatively cheap/easy fix. and if anyone else has input or experience keep it coming
 

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2018 Sierra Denali
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755 Posts
Discussion Starter · #6 ·
The light does not remain up after it blinks. I have a handle programmer and it is showing that there are no codes. Asked Autozone if they could read a code that was stored without the engine light actively lit up and they stated that they could not.
 

· Supr Moderator AutoTech SS-Guru Mbr Extraordinaire
2015 High Country Duramax
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If the light was on, there should definitely be codes stored.

And auto zone is full of it because I know for a fact that they can see stored codes.

A flashing engine light can indicate a misfire condition. My torque app will read stored codes as well as active codes obviously.
 

· Registered
2018 Sierra Denali
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755 Posts
Discussion Starter · #8 ·
I ordered my own code reader. Much easier that way.

Hope I have a bad plug or wire and its an easy fix. I feel like it should be with how intermittent the problem is and how it is still running great minus periodically and only in certain situations

Thanks everyone for the assistance
 

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509 Posts
My handheld has live data so i can watch it while driving/engine running, and also records the whole time its plugged in. Does yours have the option to watch as your driving, or were you can review it and see whats happening when it does it? just a thought.
 

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2018 Sierra Denali
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755 Posts
Discussion Starter · #10 ·
It is just a cheap one that came with the supercharger, not even sure on what brand. The only reason I keep it around is to read codes other than that is pretty much a paperweight to me. The truck was dyno tuned using HP Tuners. I could look into it and see if I can, the code reader should be here tomorrow hopefully and I am hoping that it can pull a code out of the computer for a starting point
 
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