Misfire data log

boost88

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So one night I started getting a random break up at WOT. What parameters should I be data logging to check this? Hardware i have is an SCT xcal 3 and live link. I also have a wideband.

I tried data logging using the Ford misfire PID in live link and got some odd results. For example the picture below will show a spike. That value though isn't a basic "1" it shoots to like 54k for a split second and returns to normal. However that value changes. Sometimes it's half that or less.

On a data log wot pull I have everything seems good except for the rpm. You can see each dip when the car breaks up. I'll post a picture of that too. No change in stft, ltft or spark, timing nothing just a normal good looking data log. I have noticed my wideband going lean to a value of 1 lamba on these instances. Normal WOT shows .84ish lamba which is good just those small blips. (Wide band is on driver side after LT collector)

Any thoughts or help.
20221026_165558.jpeg


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boost88

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Yellow line is RPM signal. You can see the dips I'm speaking of which correlate to my drop on power. I also have thr CSV if anyone wants to take a peak at it. I know it's not the tune decipha has it dialed in and I've made great power on this same tune. He just a little busy right now and out of pocket for a while
unknown-19.jpeg


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DSG2003Mach1

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misfire out of nowhere Id throw in fresh plugs at the correct gap, I went hammer down the other day and it broke up bad around 5,500. Fresh plugs and good to go.

Depending on age could be weak coils as well.

The O2 sensors read oxygen, not fuel, a misfire where you don't get a good burn will leave a bunch of unburned oxygen going out and it'll read lean.
 

boost88

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Thank you. Here's a plug picture they're about a year ish old with maybe 3k miles. I'm running e85 on them but I've never been told I needed different plugs for e.

Coil packs were a Chinese brand about 1 year old but I swapped to my Motorcraft ones same issue. Ford racing 9mm wires about the same age as well.
20220929_164508.jpeg


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DSG2003Mach1

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as mentioned - that gap looks pretty big on a boosted car and they're definitely due to be replaced
 

DSG2003Mach1

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1) it would help a lot to tell us exactly wtf you have and what mods
2) I'd check with the tuner what plugs and gap he recommends
3) I still vote for those plugs look done
 

boost88

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Mods are e85, short runner, imrc delete, long tubes, x pipe, 4.30s and full under drive pulleys. Soon will have cams. On a b head cobra stock bottom end and heads


And I'll look into new plugs and see what decipha recommends

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2003RedfireVert

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I always ran .045 gap when I was NA in my GT (Ford called for a .054 which I believe is the same as the 96-98 Cobras). I still vote new plugs gapped properly/shorter than OEM. I wonder if these older ECUs will even register a misfire if the Coil fires properly. I'm unsure on that.

What is the actual gap on that plug? Looks wider than .054 but hard to tell from pics.
 

boost88

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I also just checked and my coil packs are 1k ohm out of the 6.5-11.5k ohm spec. Looks like that could be an issue too. They're 27 year old Motorcraft. And the cheap China ones I have read the same or worse

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boost88

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Update. Have some new autolite 764s I'm throwing in. I also changed the fuel filter because I've heard on older cars you can get some cleaning action when switching to E85 and they can clog. Cut the old one open though and it looked great.

However I checked with a plug gap tool this time and discovered this.... so thank you all because you may have been on to something
20221028_161116.jpeg
20221028_155024.jpeg
20221028_155022.jpeg


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DSG2003Mach1

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Update. Have some new autolite 764s I'm throwing in. I also changed the fuel filter because I've heard on older cars you can get some cleaning action when switching to E85 and they can clog. Cut the old one open though and it looked great.

However I checked with a plug gap tool this time and discovered this.... so thank you all because you may have been on to something View attachment 1766941View attachment 1766942View attachment 1766943

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Honestly I think the dirty fuel filter thing is insanely exaggerated in more modern tanks. I can’t recall seeing a vehicle from say the middle 90s on having their issues fixed because a fuel filter was dirty
 

boost88

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Most of that info I found was forum posts on jdm places. I'm still pretty new to e85 and thought it was worth looking into. But yeah doesn't appear to be an issue at all.

I'll just continue with the plugs as planned and see if it works. If not most likely look into the coil packs/wires. Probably end up ditching them this winter anyway. It's tough to find the Motorcraft wires and the coil packs. COP is much easier and it looks better too

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2003RedfireVert

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Most of that info I found was forum posts on jdm places. I'm still pretty new to e85 and thought it was worth looking into. But yeah doesn't appear to be an issue at all.

I'll just continue with the plugs as planned and see if it works. If not most likely look into the coil packs/wires. Probably end up ditching them this winter anyway. It's tough to find the Motorcraft wires and the coil packs. COP is much easier and it looks better too

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Can the pre-COP ECMs be tuned with COP ignition/harness/wiring?
 

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