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432WHP But Slight Miss/Stumble @ 6500 RPM WOT (datalog)

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smbgsx

Proven Member
225
42
Apr 15, 2017
Richfield, Minnesota
I just switched to e85 and had a tune done. the car pulls good and cruises very good 99% of the time. there are some issues that have started recently though including...
when I go WOT I have a stumble/miss at 6500 basically on the dot everytime. the whole fuel system was just redone and I switched to ecmlink's SD kit with the Omni 4-bar MAP sensor. I've went through about 4 tanks of gas before all this started happening.

some other things I've noticed are...

high (sometimes irradic) idle (1500-2000 depending on outside temp and if I sit in traffic)
some minor bucking at low load/rpm and low throttle.
ecmlink says my throttle position is at 10% when I'm totally off the pedal.
ecmlink's AFRestimate seems crazy lean to me, sometimes 21.4:1. I do have a wideband that's reporting 14.7ish at idle. (which i'm assuming is just the controller multiplying whatever lambda its getting by 14.7 for the analog gauge reading. i'd think with typical e85 id be idling around 10:1 maybe)

the new fuel system consists of a full blown billet dual pump hangar with braided -8 feed/ -6 return
walbro 450LPH rewired directly to the battery, ID1700cc injectors with magnus rail.
aeromotive A1000 regulator (which was used but seems to be working well)
ignition coils were new and only have about 400 miles on them.

I have a datalog of a few pulls and you can see the 02 voltage drop at 6500rpm under load. i'm not very experienced with diagnosis of datalogs and would appreciate any help I get. in the meantime would these be appropriate to start with??
-check plugs for fouling or maybe decrease gap (BPR7ES)
-could a failing alternator cause a current drop large enough to not supply proper voltage to the fuel pump or ignition coils and cause a miss under load?
 

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  • log.2017.miss-pull.elg
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My alternator is failing but it's still enough to pull my car solid to 7500 every time, You're dropping 1 degree of timing at that exact moment of the miss, I'm not sure why.

What are your plugs gapped at?
 
I didn't gap the plugs, I just threw a box of new plugs in the car when I dropped it off to be tuned. I'm gonna pull them out and check the condition and gap tomorrow. Thanks for checking out the log. Does my o2 sensor or estimated AFRs look funky to you? Also, shouldn't my IAT be reporting actual temp to my ecu and not be locked at 77 degrees?
 
I'm not an SD guy, so I'm only comfortable pointing out things that don't look correct to me. There's actually a template that SHOULD be filled out before you post any ECMlink logs.. but I think you didn't get a chance to see that because you're posted in the newbie forums.

I didn't gap the plugs, I just threw a box of new plugs in the car when I dropped it off to be tuned.

That concerns me, plugs should always be checked for cracks in the porcelain and made sure the gaps are correct. plus if your running 33psi like your log suggests, then they should be gapped down anyway. Mine are gapped at .018 which is a lot tighten than they come out of the box.
 
thanks for the reply, i'm running 23 psi tho. and it was at a somewhat reputable shop so I would have hoped they gapped them properly when they put them in before it hit the dyno. but I'm gonna have to check myself. I feel like it may be the problem because it started after maybe 300-500 miles of street driving. I also let my car idle a lot on start up and the coolant/oil temp rarely gets over 210 degrees. so maybe they're just fouled up. but would that miss always happen in the same spot if that were the case? i'd think it would happen in different places and get worse and worse.
 
Get rid of the Protuding plugs. Get yourself some BR7ES. You will need to close your gap some though instead of running the typical .028. There really isn't a sweet spot as every car is different when it comes down to being modified and plug gap size.
 
Is it happens when you switch gears in between them or as soon as you get to 6500 under full load?
 
Was just about to say plugs or wires. Had same issue in addition to other symptoms.
 
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