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Thread: He y'all. Trying to get my truck tuned out but cant seem to get it to stop misfiring

  1. #101
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    So I've started having an issue with my truck not firing on a single cylinder, the wierd part is that all the wiring is intact from what I can tell. I checked for grounds on the wiring and the only one that has anything is the one that is suppose to. Its cylinder 6. I have a spark tester inline with it, so I can visually see if there is one. The truck is not throwing a code and not saying anything about a misfire. Anyone have an idea? here is the current tune that I have programmed in the truck.
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  2. #102
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    From your lack of pe and 22 degrees of timing I would say time for a compression check. Why you running it so lean?

  3. #103
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    Not sure, the right bank is running really lean but I feel like thats a lack of not having spark and nothing being sent to the cylinder. I'll run a log on it tonight and let you see what I see. I still have the spark testing light in line with cylinder six. I did order a new crankshaft position sensor today to be installed tomorrow. Cylinder 4 did this before for no apparent reason, but Cylinder 4 is still firing now, just not six. I pulled the harness off from the passenger bank and did a though look at the cabling, to no avail. I feel like I'm chasing a rabbit and not catching it. I'll run another CASE relearn tonight before the run, to make sure its not something simple. I'll look into getting a compression check performed on all cylinders to check to see if there are any differences between them. I did pull the rocker cover off the passenger side, nothing was amiss. Thanks for the assistance again.

  4. #104
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    Mecanicman here is the log file from tonight. At the beginning cylinder 6 didn't fire for a bit and then started firing again. When i say not firing, I mean no spark with the test light still in place. After that it started firing normally without hesitation. I did some almost full throttle runs with it to populate the tables. If you have any suggestions, please don't hesitate to tell this nub. Thanks again for all the help in the past.
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  5. #105
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    Looks like you gave up on adjusting ve table and raped the pe table? Your commanding 12.92 and hitting 11.5. You can hold off on compression test. Your tune had me more worried then the scan doesl. Move your coil pack from cylinder 6 to another cylinder and see if problem follows.

  6. #106
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    I tried that, and the problem still existed on cylinder 6. Checked for any grounds on cylinder 6 and only had the one ground that is suppose to exist based on the color and the electrical diagram for AllDataDIY and the Haynes manual. There is another but its the low reference. I've still been adjusting my VE table a bit, and then smoothing it out. The weather has been a bit crazy from 50 at night to 70-80 during the day. With the colder weather the differences are a bit annoying to keep track of. As for the PE I did rape it a bit, I was attempting to adjust the AFR to prevent it from getting crazy. I'll check what the Tuner and the LM-2 are reading to see how close they are, maybe the wideband is differing a bit which would be causing it to need a VE table adjustment.

  7. #107
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    Tweeked a few things in the DTCs and removed the ability for the Cats to be monitored. I dont know whether or not to re-enable the MAF sensor would help or my VE table needs more work first. attached are the log for a run and the tune is post log with the VE corrections multiplied minus half. IAT was definitely a bit high, weather here has been all over the place. I'll try and get a good log with the tune and post it. Hopefully cylinder 6 will start working correctly. I did purchase a stock ignition coil and see if the coil is the issue or something else. Also I was told by a friend that has seen issues with the harmonic balancer free spinning on the crankshaft and curious if thats an absolute or opinion based? Thanks again for anything and everything.
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  8. #108
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    Here are two logs I ran earlier, with cylinder 6 still not firing 100% of the time. I also noted the ambient temp based off the vehicle RTD located before the radiator.

  9. #109
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    You need to solve your cylinder 6 issue, I would not continue driving it like this. Your tune was looking better before. Go back to your old pe settings and tune the ve.

  10. #110
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    will do. as for the cylinder 6 issues, what would you suggest looking at, I can try doing a swap again with another cylinder. Any other ideas?

  11. #111
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    I restored the PE table back to what it was previous. Ran the truck for a bit, getting into boost before it booged down. I was able to get the cylinder 6 'misfire' but it still comes in once I turn it over being hot, after idling for a minute or two it stops. Still troubleshooting that. Attached is a log and the tune prior and post run, using the past percentage not minus half. Any words of advice, please feel free to correct me.
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  12. #112
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    Fix cylinder 6 first. It will skew results and you could be doing damage.

  13. #113
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    Understood.

    10/3. Cylinder 6 issue seems to have been resolved. I had some older MSD coil packs sitting in a box. Did a swap with cylinder 6. Fired up no issues, drove it around a bit. Shut it down and started it back up 15 mins or so later. Fired up no issues. No idea if there is a circuit board that was overheating but doesn't seem to be an issue anymore. MSD didn't really pay attention to the coil packs they were replacing, when a heat sink is on top of the stock ones, after market ones should meet or exceed functionality. That being said I picked up "The Ultimate GM EFI Tuning Guide" and giving it a look. See what things I can do on my own. Once I read and do, I'll post runs and tune. Thanks again for everything Mecanicman, for everything you've given me for assistance.
    Last edited by kawilliams06; 10-03-2014 at 02:47 AM.

  14. #114
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    So after getting cylinder 6 to fire correctly by swapping another coil I had in the garage with cylinder 6, attached is the results log and the tune I'm currently working with. I did change the pulley from a 3.4 to 2.8 inch. I pinned the crankshaft to the harmonic balancer. Right now I'm trying to figure out what I can do so that I can get more power when I get over 160 kpa, the truck gets into a fit and I have to release throttle before I'll play right again.
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  15. #115
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    So did some logging and tweeking of the VE table and messed a little with the spark tables. The issue I'm having now is that at about 6-7 psi the truck loses power and feels like it sputters out. Also going uphill at around 4 psi is does the same. Not sure what needs to be adjusted. I did touch the PE and BE tables but other than having AFR around 12.0 to 11.5ish under boost, nothing else I've touched seems to help. Any opinions?
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  16. #116
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    Your ve needs lots of work, your pe settings are not realistic, your miss is not gone, and your scanning a bunch of useless pids that are slowing down your scanner and skewing your results.

    Get rid of calculated load, both maf pids, both iac pids, ldle stit, all the fuel trims, fuel trim cell, delivered engine torque, trans fluid temp, baro.

    I still dont trust your wideband, your narrow bands dont agree with it.

  17. #117
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    Sorry for the delay in response. I ran the truck a few times, and I feel like I resolved the issue of the misfire. attached are the tune with the log applied that is also attached. The only thing I've noticed is under boost the truck feels like it surges a litttle, nothing I could see that was very clear on the log. The pulley size was changed with the supercharger and the harmonic balancer is pinned to the crankshaft now. I re-gapped the plugs to 0.22. Looking to get some BR7EF plugs soon, just have to find somewhere that has them.
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  18. #118
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    so looking at the logs and thinking about everything that is going on that I'm trying to resolve, I wondering if my engine load is the reason the truck stops accelerating until I let off the throttle a bit. attached is a log a ran last night, and at 6 1/2 minutes into the run, the calculated engine load is 100% and only putting out 4 lbs or so of boost. Could this be the reason for me note being able to accelerate more? I'm only at 55% throttle. Should I go with a large pulley to be able to squeeze more power without blowing my motor? Is actual engine load the same as calculated, and is there anything I can change to allow me to have more accurate indication of actual engine load if they are not the same?
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  19. #119
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    Too much fuel and not enough timing. You need to tune ve table.

  20. #120
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    Started to look at others with a similar setup and found timing tables they were running, attached is the post-run adjusted tune and the log that was used to adjust the tune. Sorry for all the extras on the log, just wanted to see everything. will do a run with fewer info on it.
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