Misfire at idle no code

[NNBS]

Hi guys ,

my truck shakes at idle and fuel smell is so bad . truck misfire at idle but no check engine light or code present .
checked for vacuum leaks at headers and intake nothing there , changed both o2s ,fuel injectors still have problem . if could some had this issue before as I think its a mechanical issue . take a look at this o2 reading at idle tell me what you think please pic .
sierra 2.jpg

[5FDP]

Looks fine to me.

Pull the plugs and check the gap. Stock is .040, some just lower them to .035 when modded and even further when they install superchargers or turbo systems.

Raise the idle rpm by 100 rpm and see if anything changes. My nearly stock 2012 silverado shakes at idle some, to me it's just a normal thing with some of these trucks. It's not a dead miss shake but just enough to feel it sitting in the drivers seat. I have no known engine problems at just over 100,000 miles and still have stock cat converters so no extra smell.

[JBZ]

log misfires and rescan, you can log total misfires and all 8 individual cylinders. if your not getting enough to produce a P0300 code but your seeing which cylinder it is it may help in narrowing down your troubleshooting. then you can check that cylinders plugs, wires, coil packs, injectors, wiring harness so on and so forth.

[NNBS]

Thanks for the quick reply guys ,
The truck runs smooth at open loop , once it gets into close loop it shakes and fuel smell starts comming .

[Michael_D]

Did you leak check with smoke?

[NNBS]

Yes no vaccum leaks ,

[JBZ]

Thanks for the quick reply guys ,
The truck runs smooth at open loop , once it gets into close loop it shakes and fuel smell starts comming .

its probably swinging to fast at idle and the RPM is bouncing due to rich/lean swings. Try increasing your integrator delay in the idle areas.

[NNBS]

I'll try that

[ABADZL1]

I've never seen a bad coil on a 5.3 throw a code. Don't rule that out.

[JBZ]

I've never seen a bad coil on a 5.3 throw a code. Don't rule that out.

That could be it as well

@ OP if you are logging misfires per cylinder you can track which one is the offending cylinder. Than move the coil pack, plug or wires to see if the misfire tracks to another cylinder. Easy way to troubleshoot that.

[NNBS]

misfire.hplmisfire is in every cylinder ,random.
take a look at the log file .

please note that ltft at idle is tuned ,it was at 12% .

[SultanHassanMasTuning]

its normal to see misfire counts you need to adjust the tables

[NNBS]

the problem is the engine shaking at idle with no code ,

[SultanHassanMasTuning]

check is code is disbaled

[NNBS]

code is enabled ,
replaced both o2 , 2 sets of injectors , plugs , wires , intake manifold , map sensor , maf sensor ,coils , lifters ,ecu , I even sold my engine to my friend and he install it "no single misfire or a shake in his truck". I bought a 6.2 l92 engine instead of 5.3 and still the same misfire . by the way i went to a shop that have a lot of gm trucks and checked around 10 trucks non of them even you can feel the engine running .

[5FDP]

Try a cam/crank relearn just for kicks and see what happens.