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Discussion Starter · #1 ·
This issue has been developing for a month or so now but now more frequent. When coming into boost it would stutter but now when i get into it at all it does it. AFR's are around 8 when in boost and 14-15 normal driving. It got worse after a "F* around and find out" session with a BMW and Mustang. I don't think I broke anything as it drives fine when not in boost and when no load is present. I think I'm gonna start with plugs and then maybe aux pump. Any help would be appreciated.
 

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could have a plug missing, also AFR at 8 i assume ur on ethanol ? what lambda ? i don't like to use AFR, if ur only on petrol at 8 AFR then ur crazy rich
 

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Discussion Starter · #3 ·
At the time it was on 93 but it is set up for e85 as well. When the weather is better I will take it to see. I’ve got new plugs on the way.
 

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Discussion Starter · #6 ·
8 is what it was on at the time I will switch it to lamda and see when the weather is nicer. The car was tuned prior to me purchasing the vehicle but I have an appointment with my tuner in a month.
 

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I'm not a tuning expert yet, but I don't think you want an 8 lambda on gasoline! I would pull the plugs and nake sure they still have the straps on them.
.8 Lambda for WOT or 11.76 AFR on gas. I run mine a little richer at .78 and tune my own. Most run around .75 to.8 from what I have seen. Depends on your tuner.

8 AFR puts you about 12.05 AFR on E85 and is still a bit lean IMHO. But I'm not a professional tuner and don't run Corn. Again depends on your tuner and how it was set up.
 

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since u mentioned 8 AFR as well as 14-15 AFR when not on boost that shows like its normal closed loop stoich for petrol, so the 8 is very rich and will cause stumbles as its almost 45% increase in fuel over stoich should only be about 20% depending on mods/fuel, also is this a commanded AFR or actual wideband ur reading ? if its wideband set it to lambda and then it wont matter what fuel u are using it will show true, if it shows lambda 0.544 then ur crazy rich but if its 0.800 then ur fine, if u can cause the issue close to your house and shut engine off as soon as possible then when u pull the plugs u should be able to see a color difference on the affected cylinders so u can check out whats going on
 
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Discussion Starter · #11 ·
since u mentioned 8 AFR as well as 14-15 AFR when not on boost that shows like its normal closed loop stoich for petrol, so the 8 is very rich and will cause stumbles as its almost 45% increase in fuel over stoich should only be about 20% depending on mods/fuel, also is this a commanded AFR or actual wideband ur reading ? if its wideband set it to lambda and then it wont matter what fuel u are using it will show true, if it shows lambda 0.544 then ur crazy rich but if its 0.800 then ur fine, if u can cause the issue close to your house and shut engine off as soon as possible then when u pull the plugs u should be able to see a color difference on the affected cylinders so u can check out whats going on
Pulled the plugs, 6 and 8 were the only ones like this. Lambda runs around .88 - 1.04.
 

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Well you found your problem. Replace them and see if you still have the stumble. Check for misses also. Not sure if you have HPTuners or an Aeroforce gauge.
 

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Discussion Starter · #14 ·
Uh oh. Those straps WENT somehwere, too. 😬
scoped the bores and saw nothing that would indicate that they broke off and were bouncing around or anything. I will cut open oil filter and see if I can find anything.
 

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Discussion Starter · #15 ·

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check lambda at 0.88 at wot as it may be ok on ethanol but petrol wouldnt last that lean in boost, u may have a PE petrol and ethanol table so u can make the petrol richer at least 0.80 or u can go that for ethanol as well as it will help with cooling anyway then ur safe both ways, unless ur full built for boost its good to keep those cylinder a bit cooler if u want it to last longer
 
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