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Evo 8 stutters and goes lean above 20 psi.All of a sudden.

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Old Jan 20, 2018, 04:15 PM
  #16  
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Originally Posted by Biggiesacks View Post
Is this 91 or e85? If your trims are pulling fuel like you said that would make me think blend change on e85. -11 is pulling alot of fuel, where you able to verify if the ecu was hitting stoich when it was pulling that much fuel? If you change your scaling back to the way it was before compensating for the trims, clear them out by pulling the battery and then testing, does the problem persist?
Well the cars been tuned on speed denaity for months. Then out of nowere i felt this issue and then the check engine light set for fuel trims on same night.

So i adjusted the latency to bring trims closer to 5 percent. Problem still there.

So it still misfires or stutters but it seems to have gotten better. But i may just be lying to my self. Also injectors were cleaned and benched about a month ago.
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Old Jan 20, 2018, 04:25 PM
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What are your afr's doing durring the pull? Do they look good?
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Old Jan 20, 2018, 04:46 PM
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Originally Posted by Biggiesacks View Post
What are your afr's doing durring the pull? Do they look good?
So im doing 2nd gear pulls from around 2500 rpm WIDE OPEN THROTTLE and afrs are in check. Around the time i hear my wastegate 20 psi or so it bucks/misfires/stutters. And afrs spike up lean.

From target 11.5 or so to 12.6 then i let off. Dont wana make a crank window
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Old Jan 20, 2018, 04:48 PM
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I would assume a misfire would spike rich because of the unburnt fuel in the exhaust stream but i may be wrong.

I read a thread by razorlab or mrfred with similar issue. His ended up being Cam sensor but i already swapped
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Old Jan 20, 2018, 04:57 PM
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Yah I agree you would think a Miss fire would spike rich. If it was me I would crank the boost all the way down and try and see how the afr's respond to tuning. That is if I was pretty sure it's not a mechanical issue. You can test that the pump is getting full voltage durring cranking. It should spike full power then drop off a second or two after it starts and stabilizes. Also you should check all your vacuum lines especially the ones going from manifold to valve to fuel pressure regulator
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Old Jan 20, 2018, 05:02 PM
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Originally Posted by Biggiesacks View Post
Yah I agree you would think a Miss fire would spike rich. If it was me I would crank the boost all the way down and try and see how the afr's respond to tuning. That is if I was pretty sure it's not a mechanical issue. You can test that the pump is getting full voltage durring cranking. It should spike full power then drop off a second or two after it starts and stabilizes. Also you should check all your vacuum lines especially the ones going from manifold to valve to fuel pressure regulator
All vaccum lines are good and ziptied.
Ill check pump voltage next.

Im almost sure dropping the boost would make it run normal. But what will that point to?
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Old Jan 20, 2018, 05:08 PM
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I would think it would point to needing more fuel in the higher load cell areas. If you can dial in more fuel and your afr's respond as expected then that's probably all you needed, if however they don't then that would point to a mechanical problem.From a high level though it sounds like you threw a code for running too rich so you pulled fuel, and now your running too lean, so maybe the problem wasn't you where too rich in the first place, but some other issue was throwing off the trims. That was kind of what I was getting at when I asked if you where actually hitting stoich with that -11 trim. I will add that changing injectors scaling/latency will almost for sure call for some retuning of the fuel map
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Old Jan 20, 2018, 05:17 PM
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Originally Posted by Biggiesacks View Post
I would think it would point to needing more fuel in the higher load cell areas. If you can dial in more fuel and your afr's respond as expected then that's probably all you needed, if however they don't then that would point to a mechanical problem.From a high level though it sounds like you threw a code for running too rich so you pulled fuel, and now your running too lean, so maybe the problem wasn't you where too rich in the first place, but some other issue was throwing off the trims. That was kind of what I was getting at when I asked if you where actually hitting stoich with that -11 trim. I will add that changing injectors scaling/latency will almost for sure call for some retuning of the fuel map
With the code set it still spiked lean during the sputter.

I also think its mechanical but dont know were else to look. Im gonna try my brothers spollin up cop kit. See if it helps
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Old Jan 20, 2018, 05:38 PM
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Running rich on idle / cruise and lean under load could be regulator related, as it's suppose to pull some psi under vacuum and add psi with boost
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Old Jan 20, 2018, 06:51 PM
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Originally Posted by Biggiesacks View Post
Running rich on idle / cruise and lean under load could be regulator related, as it's suppose to pull some psi under vacuum and add psi with boost
Idle is perfect afr and cruise afr is good also.

I can also part throttle all the way to redline and no sputter and perfect afrs
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Old Jan 20, 2018, 09:41 PM
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Originally Posted by 4b11slayer View Post
Idle is perfect afr and cruise afr is good also.

I can also part throttle all the way to redline and no sputter and perfect afrs
It sounds like a pump problem or clogging problem.
I had the same issue before and it turned out to be a bad walbro.

Try swapping pumps.
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Old Jan 20, 2018, 11:28 PM
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Originally Posted by Evo9_Dubai View Post
It sounds like a pump problem or clogging problem.
I had the same issue before and it turned out to be a bad walbro.

Try swapping pumps.
Pump has less then 8k miles. But ill try
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Old Jan 21, 2018, 01:15 AM
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Also, I had an evox show the same symptoms, swapped pumps and it didn't fix it. It turned out to be the injector resistor that went bad. Unless you have that deleted, I'd try to swap that.
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Old Jan 21, 2018, 01:47 AM
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A misfire causes a lean spike not a rich spike.


So it's misfiring because the AFR isn't right, the logger shows lean afterwards.


Your fuel pressure will be wrong of course......lol.
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Old Jan 21, 2018, 06:52 AM
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Reason I said rich on idle/cruise is because you said this started with you throwing a code for trims and they where -11 which means the computer is pulling fuel because it was rich under closed loop. When you rescaled though that compensated.
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