Misfire after longtube header install

2017Sierra1500 · October 13, 2018

Installed Pacesetter longtubes and ran true duals on my 2017 Sierra 5.3 today. I did not install my rear oxygen sensors because I assumed that it would run fine off of the front sensors like every other vehicle i have. I did not get it tuned yet but before I even got home from the garage the truck is running like shit And throwing a code for cyl 7 misfire, along with all the codes that come with the rear o2’s being unhooked.

Can anyone tell me if these are related , or is it just coincidence that it happened right after? Truck has 27 thousand km’s. Thanks in advance.

cmysstailights · October 13, 2018

Check the spark plug wires. I had a similar miss on my camaro and i forgot to hook up the injector wire. Check all connections. Swap coils and see if miss follows.

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2017Sierra1500 · October 13, 2018

Swapped wires but did not have time to swap coils, nothing else was unhooked besides the plug wires.

Centex14 · October 14, 2018

I’d get everything hooked up and tuned before troubleshooting any farther.

2014 z71 LTZ
Volant Intake
Borla Exhaust
Diablo
Bilstein 5100
Rough Country Level

2017Sierra1500 · October 14, 2018

Alright , I was hoping to not have to use the local tuner but looks I’ll have to.

Centex14 · October 14, 2018

You should be able to get an email tune. Black bear or Lew or several others.

2014 z71 LTZ
Volant Intake
Borla Exhaust
Diablo
Bilstein 5100
Rough Country Level

cmysstailights · October 16, 2018

Alright , I was hoping to not have to use the local tuner but looks I’ll have to.

Its ur best bet, they use a sniffer for a/f

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EJPolaski · October 19, 2018

Off topic, but are you satisfied with the fit/finish of that brand?

2017Sierra1500 · October 22, 2018

Found a cracked plug causing my misfire. Fixed that and it runs great other than the cel. On the drivers side we had to go in from the top and on the transition from holding it from the top to grabbing it from the bottom we banged it around a little so that must have been when it happened.

Couldn’t be happier with the pacesetters. They look awesome and installed rather nicely. Now I’m attempting to quiet it down some. I went with true duals off of the collectors with an H pipe and 7” flowmaster outlaws. Sounds unreal at WOT, and from idle up to 2000 rpm. Hoping an x pipe will get rid of my blatting and snapping or at least tone it down.