*SOLVED* Inconsistent power output
 

Hey all, I've tried many things and need help.

2017 BRZ manual performance package 45k miles
Catless plm header, srs over pipe, flex fuel kit

Most of the time the car runs like the symptoms below except maybe every 3 to 4 weeks, it'll run like a f****** dream for about 3 days and then it goes back to running like a disaster.

Symptoms/when the car runs like crap:

No CEL
Sluggish acceleration through out rpm band
Rough first gear start do to less responsive gas pedal
Revs drop noticeably quicker between shifts which makes shifts rough
Car sounds very raspy and louder than normal

When the car runs excellent:

Power and strong acceleration everywhere
(Even with the first engine start I can already tell it'll run great because it revs up stronger when I start it)
Gas pedal very responsive, first gear start like butter
Rev drop normal, smooth shifts
Car sounds clean and healthy, all you hear is the crisp rumble

What I've done:

new MAF
new upstream AF sensor
Checked back pressure for restriction (had a header cat collapse which made the front pipe cat collapse as well but all this was solved since then and the tune was updated for the current header)
Checked exhaust leaks, vacuum leaks

I've ran it on 3 different tunes, which were reviewed by the tuners who said everything's running like it should.

Coincidentally the last time it started running great all of a sudden was after I took out the air filter box to check vacuum leaks, I flipped the filter, put everything back and car ran good but no surprise to me, 3 to 4 days later, it's back to being a mess.
Weather doesn't seem to have and impact because it has ran great/awful in both high 90s and low 40s.

Any specific log would help?

Bubba says to remove the air filter for a few miles and see how it runs.

The results just may lead you to the problem.

:iono:

really sounds like un-metered air is entering the motor somewhere, so the a/f ratio is getting thrown off

haha I appreciate bubba but that doesn't seem safe :eyebulge:

this one is when it runs bad

http://datazap.me/u/stix/2nd-gear-pu...?log=0&data=31

this one is when it runs good

http://datazap.me/u/stix/2nd-gear-pu...?log=0&data=31

And yes vacuum leak was my main concern but I just can't find anything unless I'm missing something very small since there are no codes

I had this same issue on my 2017 86 for nearly a year. I tried all kinds of things, even swapped out the throttle body for an aftermarket one. Then one day about a year ago I installed a K24 into the car and my throttle response has been great ever since. When it's not very responsive feeling, are you able to go full throttle and back to no throttle real quick without the engine revving, as If the pedal isn't registering? Mine would do that. For my car it was as if there was a half second delay on inputs with the pedal.

those every 3-4 weeks you wouldn't happen to be disconnecting your battery, would you

Yes I am able to do that, I think for me it has more to do with the power loss. Glad you got fixed it though

No, definitely not

Are you running low on fuel when this happens? Like below 1/4 tank?

No, it happens at all levels of fuel. E5 or 93 it doesn't matter

Inconsistent power output
 

You need to log correct perimeters. There is not enough info in the logs to tell anything. Not sure if there is going to be anything to see being it is not tripping CEL. These are the funnest types of problems.

Engine Speed (rpm)
Throttle (percent)
MAF Voltage (volts)
Engine Load (g/rev)
Ignition Advance / Total Timing (degrees)
AFR
Commanded AFR
LTFT
Oil Temp
Fuel Sys Status
IAT
IAM Advance Multiplier
FLKC

Ok thanks I'll have these logs ready tonight

new logs

warm idle
http://datazap.me/u/stix/warm-idle?log=0&data=4

normal driving
http://datazap.me/u/stix/normal-driving?log=0&data=4

Cams sticking?

From my limited knowledge nothing really stands out except for the way the ignition advance is fluctuating. I am not a tuner/tuning expert so I can't really comment on how normal that is. IAM is steady, LTFT look fine, AFR is following command, no knock correction. :iono: I would think if it was an AVCS issue it would pop a code.

Would a bad crank sensor cause the timing to fluctuate?

Not sure. I am not even entirely certain it’s not normal. It just looks odd to me.

Yeah that's the thing, it looks normal for the most part..

How can you tell?

I think a data log should show it. Sticky cams were an issue early on.

There is a case that AVCS does not work but no code. It does not move even in the active testing in Techstream.

https://www.ft86club.com/forums/showthread.php?t=138803

Even if my logs show vvt enabled 1?

I just dropped my exhaust to check for restrictions just because I had a cat go bad once and thought debris might be stuck in the pipe but nothing there. Rode around with muffler disconnected and also nothing changed.

I haven't read everything, so I hope its not a repeat.

I would put a different, mostly basic map. One that will work for your exhaust and intake for sure, but just a basic off the shelf map from the car.

UPDATE for anyone still interested

Flashed a stock 2017 ecutek map and I couldn't believe how much better the car ran. Even with the torque dip and all I have better acceleration and responsiveness and it's actually fun to drive again NOTE that I've ran 3 different tunes from 3 different reputable tuners (2 tuned it remotely and said everything looks fine) but all 3 have made my car run terrible before flashing the stock tune, which feels like an upgrade as crazy as it sounds. I'm positive the tunes aren't the problem and something else is f****** with me but what?

What gives?

I hope someone has a clue.

Very odd. My car throttle feels significantly better tuned vs stock, along with overall powerband.

My tuner switched me over to a euro ROM when I tuned with ecutek. Cannot comment on the exact differences between USDM and EURO ROMs as I don't have the technical know-how. Dumbed down answer I was given is that it's less buggy.

Maybe somebody can shed more light on the difference. @tomm.brz ?

Bugs are related to racerom patch applied to >17 US oem map, so an unpatched rom as his doesn t have problem

i think it s case is that he just doesn t like the tunes he got from those tuners, and maybe the were not objectively well done :) oem tunes are very refined under 3000 rpm, and it s very much easy to mess up with smoothess and bogging down at low rpm if you don t spend time to improve it

That's not the case man. If you read my previous posts, the car runs perfect for about a couple days and then runs like it's on 3 cylinders for weeks until back to normal for a couple days again. I'm pretty sure you wouldn't be thrilled with your car running with the symptoms I listed earlier either..

i'm just going over everything in this thread again because it still makes little sense.

it sounds like you've already checked your air box. doesn't sound like you have an aftermarket/modded intake at all. that should rule out vacuum leak. should.

the temperature has been wild around here, but you indicate it does it at intervals not in line with specific temps.

you said you've got an e85 kit--correct me if i'm wrong, but doesn't the e85 kit require a tune to correctly interface to read the ethanol content of the fuel and adjust fuel trims accordingly?

the stock tune wouldn't include that component.

could it be your e85 content sensor is mucking up the fuel trims?

That's a good point maybe my flex kit is faulty. All the tunes I've been running are flex tunes so it would make sense. When I went to the stock tune I ran a tank of 93 before flashing it, and I reconnected the upstream sensor and disconnected the flex kit. I'm not sure how to test the flex sensor for accuracy.

Well to start with, did your flex readout seem reasonable when you would fill up on E85? Did you watch it and see if there was any odd fluctuation or possible misread of what you expected it to be?

I didn't keep a close eye but it looked reasonable when I'd fill it up. The only thing I noticed was that the flex app was showing 5 to 10 percent more e85 than ecutek was

Not too familiar with the app so I don't know if that's a typical discrepancy or not. But to be honest, that would seem odd. 5 to 10% is a pretty decent difference if there truly is a discrepancy there. Either way, the most important thing is what the actual flex sensor is reading. I agree with soundman that this is likely your culprit considering your problem and the solutions you've attempted.

I would contact the manufacturer of the flex fuel kit you have and discuss this with them. They may be able to provide a particular replacement part. They may also be aware of very rare cases like this and know what is likely failing in the kit.

Because from everything you describe, it definitely sounds very unusual that you are experiencing issues with the tune. I doubt your car is allergic to one. :D

I'm not sure if this is possible since you have ECU-Tek flashed on your car, but maybe you can have someone local with an OFT un-marry their device and flash it onto your car to see if that stage 2+ tune presents the same issues?

Also I believe most of the vacuum lines are underneath the intake manifold if you wanted to take a look at that. Do you get bad MPG when the car isn't running right?

Yeah I'll double check, but in regards to oft I think I'd lose my ecutek license

SOLVED. I assumed my flex kit was scaled 0v-5v but it was in fact 0.5v-4.5v. I gave my tuner the wrong info, a big error on my part which caused a difference in ethanol between the sensor and ecutek of around 8%. Logs looked good but the car ran terrible and I had no answers for months. Now it's scaled correctly and it's like driving a new car. Thanks for the help y'all.

thanks for updating us, glad to hear you figured it out!

so it was the sensor after all, just an error between the obd2 port and the keyboard, instead of the sensor, which in some ways is better, as it's cheaper to fix!