Mystery Idle Misfire L83 Stg 2 cam

[gabby23]

Hello all,

I am looking for a little guidance for trouble shooting a potential problem. I have been trying to hunt this issue down and I am running out of ideas and I am hoping some people with way more experience can chime in.

Breakdown of the truck
2014 Chevy Silverado 5.3l
- 6.2 intake and throttle body
- MSD Spark plug wires
- NGK rhodium Spark Plugs
- BTR l83 Stage 2 v2 Cam
- BTR 5.3 GEN V TRUCK CAM KIT - 2241023116R1
- BTR .550" LIFT GEN V LT BEEHIVE VALVE SPRING SET - LIKE 12691120 - BTR91120-16
- BTR VALVE SEAL SET
- BTR CHROMOLY ONE-PIECE PUSHRODS - 7.850" LONG - 11/32" DIAMETER - .080" WALL
- BTR GEN V LT VVT PHASER LIMITER - 4 DEGREES - BTR-VVT-GENV-4CAM
- BTR CAM RETAINER PLATE - LIKE 12589016 - BTR89016
- CBI STREETCARS DOD CONVERSION PLUG SET - GEN IV/V - CBI/OBO
- BTR GEN V LT HEAD BOLTS - COMPLETE SET - BTR/LT1/HBK
- BTR GEN V L83 HEAD GASKETS
- CHEVROLET PERFORMANCE HEADER GASKET - GEN V - 12657093
- DELPHI HYDRAULIC LIFTER SET - GEN V - X17120735
- BRIAN TOOLEY RACING LIFTER TRAYS - SET OF 4 - BTR95365
- Chevrolet Performance Balancer Bolt for Gen V LT Engines - 11547372
- BTR GEN V VALVE COVER GASKET - BTR-19787
- BTR GEN V VALLEY COVER GASKET - BTR-23104
- BTR GEN V LT CAM BOLT - LIKE 12681018 - BTR-81018
- BTR CAM RETAINER BOLTS - BTR61455-4
- SPEED ENGINEERING 2014+ SILVERADO & SIERRA 1 7/8 LONGTUBE HEADERS - 25-1037
- SPEED ENGINEERING Y PIPE - 2014-2019 SILVERADO/SIERRA - 25-1038
- New Intake and exhaust valves
- New oil pump
- New timing gears and chain/tensioner
- K&N catch Can
- K&N CAI
- MBRP single 3.5" exhaust

- rebuilt 6l80 with circle d stage 3 kit
- new circle d Pro 300mm torque converter
- multiple sonnax upgrades as well

I have been working with a tuner for almost the past year. It wasnt until late last year that I started experiencing problems. The initial issue was will cruising at hwy speed the torque converter would unlock and relock almost as if you were to hit a deep crack in the road. Long story short I believe this issue was a coil going bad and shortly after I ended up replacing all of the coils with new NGK round coil packs. Since finding this issue the tuner has had me add misfire tables to the logs. While I believe part of the issue is resolved as you can see in the log the cylinder 1 misfire amount is rather high. Now I do understand that the scanner may see a misfire on 1 and it could really be a different cylinder. So in hunt for more clarity into the issue for a hopeful resolution I have tried to fix whatever might be causing this issue.

First thought was bad plug
bought a whole new set same kind- issue still exists.
swap plug wires around and still nothing changed
checked compression and all were with in 10%, on the closer to outliers I did a leak down to confirm, all less than 5% loss
Changed to all new 6.2 injectors, compression and leakdown again with no change
changed to a new high pressure fuel pump- still no change
changed to new 02 sensors - still no change
new maf sensor - still no change
new map sensor - still no change
new evap - still no change
checked grounds and added additional/better cables

I have hunted throughout this forum and have adjusted many things and although some have helped a little none have truly changed much of anything.

I am hoping some one some where that has some experience in tuning these trucks can help get me pointed in the right direction, or possibly all of this is normal.

Things I haved considered but not done yet would be changing the thermostat, coolant temp sensor. Rev 7 2014 Silverado 5.3 BTR Stage 2 L86 airflow new table.hpt
25-06-11 21-17-40-3.hpl

[Estep40511]

I would try putting GM coils and plugs/wires in it. Ive had nothing but bad luck out of anything else on a GM motor. Also had an issue with my converter doing similar things when I first replaced it. It was in the transmission tuning though.

[gabby23]

@Estep40511, thank you for your input. Before changing all of them I did replace 3 with new ac delco coils, I rearranged them a few times on various cylinders and the misfire never moved. I can some gm wires and see what happens. Since I have replaced the coils i have not had an issue with the torque converter.

[2xLS1]

Do you understand what a cam with any lope at idle does to stock misfire diagnostics?

[gabby23]

@2xLS1, yes I do understand. According to the tuner, we were anticipating the misfire counts to appear but the issue is that the high count on only one cylinder.

[2xLS1]

Check the temperature of that cylinder header tube compared to all the other tubes with a laser thermometer

[gabby23]

@2xLS1, I have previously done this many times over the last several months. Typically the front cylinders 1& 2 are cool by comparison. Usually only a few degrees above ect. Cylinders 3,4,5 & 6 off memory are around 200 or more. Cylinder 7 & 8 usually about 10-20 lower, around 180-190. If I check after driving around for a 15-20 minutes all the header tubes are relatively consistent above 220-240.

Due to my inexperience with long tube headers, I feel that the front temps are low. Which is why I'm trying to figure this out. But I could be wrong and that could be normal. I'm hoping I can verify with others that have some more experience with these setup as to what normal is.

[2xLS1]

I think you are chasing a ghost

[gabby23]

I would believe you are correct, but the tuner believes otherwise and continues to say that I have a problem. I also have not received any conclusive evidence or parameters that the tuner is using to determine that there is in fact a problem.

This is why I am on this forum. I feel like I have at least gave a valiant effort into figuring out the so called "problem".

With this thread I am trying to hopefully confirm my suspicion and or find out other places and or things I should be checking.

I appreciate your time in helping me learn.

[relicdew]

Most tuners will change and desensitize the misfire tables that I see. see attached tune file. The only change made was to your misfire tables. Go drive it and see if this is better. I didn't do it, but I've seen other tables turn of P0300 code for random misfire detected. Your converter will unlock during a misfire event in the ECM.
Rev 7 2014 Silverado 5.3 BTR Stage 2 L86 airflow new table_misfireTable.hpt

[edcmat-l1]

I would believe you are correct, but the tuner believes otherwise and continues to say that I have a problem. I also have not received any conclusive evidence or parameters that the tuner is using to determine that there is in fact a problem.

This is why I am on this forum. I feel like I have at least gave a valiant effort into figuring out the so called "problem".

With this thread I am trying to hopefully confirm my suspicion and or find out other places and or things I should be checking.

I appreciate your time in helping me learn.

Your tooner doesn't know what he's talking about.

Love all these "my tuner" posts/threads.

You can't go by the misfire counter after you've put a cam in a vehicle. Period. Stop looking at it and thinking there's a problem. A real misfire will show up in the data in a completely different way and apparently your "tooner" doesn't know how to tell one way or the other. I'm telling you it does not look like your engine is misfiring. I don't care what the misfire counter says.

As for IR temp guns, most people don't know how to use them. If you don't hit each tube in the right spot you can have 200 deg differences between cylinders when there's actually nothing wrong. I've seen "pro" technicians do it. Seems I gotta show everyone how to use a temp gun.

Thermal imaging is the way to go. If a cylinder is just a little cooler than the rest it's completely obvious.

[Alvin]

I don't see any indications of a miss in the log.

Could you point out in the log where you feel this TCC unlock/lock thing?

[gabby23]

Most tuners will change and desensitize the misfire tables that I see. see attached tune file. The only change made was to your misfire tables. Go drive it and see if this is better. I didn't do it, but I've seen other tables turn of P0300 code for random misfire detected. Your converter will unlock during a misfire event in the ECM.
Rev 7 2014 Silverado 5.3 BTR Stage 2 L86 airflow new table_misfireTable.hpt

Thank you relicdew, I much appreciate your time in to helping me out with this issue. I will update later on this evening.

[gabby23]

Thank you edcmat-l1, I appreciate your information and thoughts. I agree with your sentiment around the misfire counter as it does become irrelevant. For the life of me I haven't found the evidence of a misfire either, but I will say im not exactly sure what to look for either. Would you be willing to share what information to look for?

I 100% agree IR temp guns are crap, but for my quick and easy comparison I think it worked out alright. Thermal imaging would definitely be the way to go but I currently do not have easy access or the available money to purchase one at this time.

Thank you again for your time and input. I really appreciate it!

[gabby23]

I don't see any indications of a miss in the log.

Could you point out in the log where you feel this TCC unlock/lock thing?

25-06-12 08-00-37-2.hpl

Alvin, I appreciate your response and I have attached a log file from this morning. I had to shorten the log to upload so for me it was just before 14 minutes in the log. It seemed weird that it didn't immediately lock back up this time. Maybe this is normal. Hopefully you are able to shed some light on the subject

Thank you!

[2xLS1]

Thank you edcmat-l1, I appreciate your information and thoughts. I agree with your sentiment around the misfire counter as it does become irrelevant. For the life of me I haven't found the evidence of a misfire either, but I will say im not exactly sure what to look for either. Would you be willing to share what information to look for?

I 100% agree IR temp guns are crap, but for my quick and easy comparison I think it worked out alright. Thermal imaging would definitely be the way to go but I currently do not have easy access or the available money to purchase one at this time.

Thank you again for your time and input. I really appreciate it!

Real misfires will show up in the narrow band O2 wave forms if you know what to look for.

[2xLS1]

25-06-12 08-00-37-2.hpl

Alvin, I appreciate your response and I have attached a log file from this morning. I had to shorten the log to upload so for me it was just before 14 minutes in the log. It seemed weird that it didn't immediately lock back up this time. Maybe this is normal. Hopefully you are able to shed some light on the subject

Thank you!

Misfires in the counters will keep the converter from locking up or cause it to unlock if locked even if they are false cause by an aftermarket cam with misfire detection diagnostics designed for a smooth rotating crankshaft reluctor.

[gabby23]

Real misfires will show up in the narrow band O2 wave forms if you know what to look for.

Okay, so please correct me if I'm wrong, from what I've been told there would be a rich spike that would be out of sync with the typical wave. If I'm wrong please enlighten me.

Thanks again.

[edcmat-l1]

Okay, so please correct me if I'm wrong, from what I've been told there would be a rich spike that would be out of sync with the typical wave. If I'm wrong please enlighten me.

Thanks again.

You're wrong. It shows up as downward V shaped spikes. The O2 sensor "sees" the raw O2 from the miss.

[gabby23]

edcmat-l1, thank you for the information!