How to Determine Which Cylinder is Misfiring Using HP Tuners

[@grominwithrob1339]

I had a pretty bad misfire on my 2010 GMC Sierra 5.3. I hooked up my Bi-Directional scan tool and identified that cyl 3 was the culprit. I swapped plugs and coils and the misfire stayed on #3. I swapped wires and the misfire moved with the wire. I went out and bought a new set of Delco Wires. Truck is running very smooth and has noticeable increase in power. I decided to hook up the scan tool and just see how everything is doing. Showed #3 has 2 misfires at idle every few cycles or so. No problem under acceleration. I decided to tweak my HP Tune because I had used it to turn off DOD and to disable flex fuel. Disabling flex fuel would obviously make the truck have to compensate for the 10% ethanol, but I figured it would be well within the PCM's ability to a just the fuel ratio. I decided to tweak it to allow a parameter of 8%-11% ethanol because our fuel is supposed to have no more than 10%. I did this and took it for a drive. Everything sounds and feels good. I hooked up my Bi-Directional scan tool and it bounced around saying I had a couple of misfires per every couple of cycles on 2 and then 5 and then 3 and then 8. It would take a few cycles at idle to show anything. Each cycle was 99 revolutions. it would register a high of 4-6 misfires per cycle and a low of 2 misfires per every couple of cycles. I hooked up my HP Tuners to do a log because I wanted to have a longer history than 99 Revolutions. HP Tuners connected showed absolutely no misfires at all. The O2 sensors on the Bi-Directional scan tool stayed pretty consistent, but the O2 sensors on the HP Tuners showed the values jumping around substantially more. I took the truck for a good long drive with the HP Tuners logging to see if I could find a misfire but after a 20min drive around town and setting the cruise on back roads at different speeds and of course sitting idle still returned no misfires. I did notice the fuel trims also where more consistent although Bank one is always calling for more fuel. Bank 2 normally calls for .8% and bank 1 calls for 5-6%. Is it possible that the Bi-Directional scan tool is wrong. Maybe after changing the flex fuel settings, the trucks ECU needs to sort out what it needs? Any Ideas?

[@burr-leeTV]

Great Info , Thank for the vid .

[@TheTuningSchool]

Thanks so much for watching!

[@digitalme4404]

My HPTuners doesn't have misfire under Engine

[@jcesparza7490]

Thanks will do this to find my issue

[@TheTuningSchool]

Awesome! Let us know if it's working for you.

[@miguelandrade909]

Many thanks and regards of México

[@ELEISONCARABALLO]

Good video. BTW, the part I didn't like: at minute 5:00 you stated ...We start replacing things like coils, plugs, plug wires......

[@TheTuningSchool]

That's right. Thanks for your feedback!

[@nickhattler8236]

Beuller?

[@White-Head]

Thanks for the info

[@mptorecon]

How about, I only have Miss fires at idle and when the A/C is on, the Miss fires increase but runs fine under normal driving conditions. Even full throttle is clean. Im running heads and 228/232 TSP cam and Hinson headers and k&n cold air.

[@dangerousfreedom4965]

mptorecon what was the fix?

[@MrDulvalius69]

I know this is old, but i get the same thing.

[@MugelloZ06]

How much variation between cylinders is conclusive evidence of a misfire? What does a stock engine look like if you ran the same scan?

[@MugelloZ06]

Would have also been useful to use the IR gun to confirm your findings. I've used these PIDs to try to diagnose a slight miss and the scanner didn't really help me. I ultimately ran the engine in pitch black and found sparks around 2 plugs.

[@fasnuf]

@@MugelloZ06 That was a smart idea looking in the dark for spark jump.

[@randyschaefer3777]

Why can't I do this for a 2006 f150? When I go to the channels list I don't have the option for individual cylinders only a total misfired channel.

[@TheTuningSchool]

The channels are not universal across all manufacture platforms and ECUs. We suggest contacting [e-mail] to see if they can assist.

[@teamanomalous6037]

Any reason why my misfire history wouldn’t be staying nor adding up the amount of total misfires ?

[@dangerousfreedom4965]

For some reason my 2006 TBSS with a large cam shows 0 misfires? Is it turned off in the tune?

[@isidrosevier1125]

407ForRent more than likely it is, most tuners will turn misfire counter off due to a big cam.

[@panagiotisf7228]

Whats an acceptable amount of misfires on a fbo 6th gen camaro cylinder 3 has 2 counts and cylinder 8 has 1

[@ryanprettyman3123]

Anything on Gen3 Hemi's?