Data logging for a misfire

[Turbo99]

My car is has a misfire and I am planning to try and log it tomorrow. I have lost 4-5mph in the 1/4 mile. I seem to be able to make it repeat sometimes, it repeats when I stay in 1 gear and hold above 4k RPM and accelerate slow and then slightly lift and then stay steady and the car just shakes and falls on its face, if I get back into the gas it clears back up but I think I feel it at WOT every time I shift the car feels flat for a seconds and then picks up. It has not thrown a code yet this is what is baffleling me.

Any suggestions on what PIDs to look at. I am thinking all the coils and TB position.

[toml_pa]

Here is an HP Tuners config file I use and some screen shots. Ignore the histograms. You want to look at the chart. The misfire cycles will count up to 100 then reset the count and misfires to 0. This continues to repeat. Once you log some data play the log, hit pause and use the scroll bar at the top of the chart to move the log to right before the cycle count hits 100. Misfires for each cylinder will be in the top chart and when added together should equal total misfires. I haven't had time to figure out how to use all these pids in a meaningful histogram yet, but this gets the job done for now. Once you isolate the cylinder, swap the plug, wire, coil, injector one at a time to another cylinder to see if the misfire follows. Good luck. Misfire.zip

[Turbo99]

Thanks. I will be using SCT but I am sure they have very similar PIDs. I was also thinking of watching the injectors as well to ensure they are firing and fuel pressure too I guess.

[Turbo99]

I am not sure if I picked the correct things, all the coils were consistant so the number 7 & 8 cyl. had the most misfires as much as 10 per second with the #8 and 6per second on #7. I did have some misfires through out all cylinders but only 1-2 max here and there but 7 & 8 would have consecutive misfires and build from 1-10 misfires in a second for several seconds.

My question is where do I start? I am thinking wires, I checked coils and they were consistent through the tests with min & max value being equal for all 8 cylinders. I thought bad gas but I have had a few tanks from different places and put water remover in and problem is still there.
Do I need to log some other PIDs?
Any help would be appreciated.

[Iam Broke]

Swap plugs with a good cyl, if no better, swap coils, then wires, then injectors one step at a time and see if the problem moves cyls to narrow it down.

If no resolve a compression and leakdown test may be in order to see if you have mechanical issues.

[etmx183]

Also get a look at STFT and LTFT they could tell you if your dealing with a lean or rich misfire. My rule is if I'm pulling a plug to check it, do a compression test while I'm there. when the misfires occur do you O2 sensors lock rich or lean?

[Turbo99]

I know it not compression, and afirly sure its not a coil. the car only has the issue at certain RPMs and only when hot. I think plugs are good but will check, but prolly going after wires first because they are by far the easiest. I am

[Turbo99]

bump

[ken53007]

Did you figure it out? I have cutouts on mine and the last couple days its been back firing at wot but I thinks its cause its misfiring if that makes any sence

[Turbo99]

I have not. I have been busy at work. I do have new plug wires MSD and will try to install today, but the passenger side looks like a bitch from the top and I don't have a lift. I may have to remove my blower water reservoir or jack the car up and try from underneath.

[Turbo99]

I got the plug wires changed to MSD wires. Not as bad as I though once I removed my Maggie reservoir. I OHM checked all the MSD wires before install and they were 23-25 ohms best to worst so very pleased with that. I removed my stock wires and found 790-1550 ohms best to worst. My number 8 which is where I was seeing repeated misfires was 1550 ohms the rest were close to each other at 790-850 ohms. Plugs looked good on all cylinders.
I will test the car today if it doesn't rain, I have to run and get some water to put back in the reservoir can't put tap water in.

[ken53007]

I think I just lost my tube or something cause it drives fine as long as I don't get into boost