Hesitation Under Partial Throttle!

[xkalelx]

subbed.

Having the same idle hunt from 600-1400rpm ONLY while on e85. Smooth idle with 93. Having stumbling/hesitation with both 93 and e85. Interested in throwing some check valves in my dual catch can lines (PCV plumbed to manifold and Crank Vent plumbed in to intake track) to see if that makes a difference. X2 on what fuel pressure regulator to upgrade to.

When running an EBCS using the EVAP harness pigtail, what does the EVAP solenoid default to? Closed?

EDIT: It DOES still hunt at idle on 93, just not as exaggerated.

[neutral]

Originally Posted by aaguirre123

I had the same problem. I have the solutions for you.


For the 750-1300 rpm fluctuations:
1) install two check valves. one between the AOS and the intake manifold (located on top of the intake manifold). If elected not to have an AOS then check valve is installed between PCV and intake manifold. Make sure that the check valve flows in the right direction. Flow direction should be from the PVC to the AOS (again if you installed one) and to the top of the intake manifold.
2) the other check valve is between the EVAP solenoid and EVAP line. The EVAP solenoid is located under the intake manifold. EVAP line is near and behind the AC compressor. By memory I think the EVAP line is between the DI and PI line. Again make sure the check valve flows in the right direction. Flow should be from EVAP line to the EVAP solenoid.
3) install clamps between the EVAP solenoid and throttle body (located under intake manifold near the throttle body).
4) Install clamps between the EVAP solenoid and the EVAP line.


In my case, which I think it's the same with yours, the reason why it fluctuates is because the EVAP solenoid is defective. The EVAP solenoid is leaking fuel fumes (gasses) from the gas tank to the intake manifold or vice versa. Working order EVAP solenoid only do two things; Open or close. Nothing in between. When the EVAP is not completely closed it creates a leak (vacuum leak). When the ECU sees a low pressure signal from the MAP sensor, it corrects this by sending more fuel and open more throttle. Hence, rpm increases. When the ECU sees pressure within normal range is reached then fuel amount is reduced. Hence, rpm decreases. Fluctuating rpm during idle is an attempt by the ECU to correct low pressure created by the defective EVAP solenoid. The ECU does not throw a CEL because either the tuner tells the ECU to ignore a drop/increase in gas pressure in the fuel tank (tuners usually disable this feature because flex fuel was installed) or it does not throw a CEL because the leak created by the defective EVAP solenoid is too low (within normal range). A minor leaking EVAP solenoid during close operation is ok with a NA engine but in a FI engine it's a nightmare.


Hesitation when transmission is on 1st gear solution:
1) change or replace the OEM fuel pressure regulator installed in the fuel pump canister.
2) 2nd option is to install an after market fuel regulator inline with the PI (port injection) line. A second aftermarket fuel regulator will make sure proper fuel pressure and volume is met.


There's hesitation because there's not enough fuel being delivered by PI.

The problem with the OEM fuel pressure regulator is that when they manufacture these parts, the tolerances are too wide during manufacturing. They are not concern about it because FR-S/BRZ are NA cars.

There's no hesitation at higher rpm because DI is being utilized. DI has an independent mechanical fuel pump so fuel pressure and volume is being met.

Tuners can't see any problems via logs because I don't think there's a fuel volume sensor or a way of sensing how much fuel volume is being delivered. When I read the logs I don't see any information regarding fuel volume; Only fuel pressure. So if the fuel pressure is within normal range and everything else are within normal range then tuners will say "There's no problem with my tune so it's not my problem. My tune is the best and I've sold my tunes around the world so I conclude that it's definitely the stupid owner's fault and/or you have a stupid car". I will not name names but some tuners are not mechanics. Many are just tuners. One of the tuner that tuned my car thought that there's a return line from the engine bay to the fuel tank. He noticed that there were three fuel lines and therefore the third line must be a return line. It's an EVAP line you dumb ass tuner.


Well I hope this fixes your problem.

So just to be 100% clear before I throw more money at this stupid car, you're saying that you had random hesitations/stumbles on partial throttle before, and you replaced the stock FPR and (without changing anything else), the problem disappeared? It's just strange to me that there's at least a handful of us in this thread, with this specific kit, having the same specific issue, while my tuner is telling me they've never seen anything like this before and it makes zero sense. I'm also $10k+ into my car and at this point I'm about ready to rip everything off and go back to NA.

[Xuningshen]

I would start by taking off the crawford AOS, and then try to get it working smoothly. Having a PCV catch can, or whatever, can do funky things, it did for me at least. Some cars don't like them so much. Having a more simple setup can be easier to get it running basic.

[Sportsguy83]

Replace the Crawford AOS,

Don't need to change the fuel pressure regulator, there's lots of people (thousands) running a turbo kit with stock regulator and no issues.

Since the car has been leak tested AND at WOT the car behaves fine with no leaning out issues, I'm pointing towards the tune BUT, it seems weird two tuners taking a crack at it and not being able to resolve it.

There is a way to test if it's the DI, you can turn the injectors off via the tune and test if the car behavior improves.

[neutral]

Originally Posted by Sportsguy83

Replace the Crawford AOS,

Don't need to change the fuel pressure regulator, there's lots of people (thousands) running a turbo kit with stock regulator and no issues.

Since the car has been leak tested AND at WOT the car behaves fine with no leaning out issues, I'm pointing towards the tune BUT, it seems weird two tuners taking a crack at it and not being able to resolve it.

There is a way to test if it's the DI, you can turn the injectors off via the tune and test if the car behavior improves.

Would DI injector leak cause this sort of semi-random crap though? My tuner said that they use DI until they need PI, so it makes sense to me why light throttle shows the issue way more than WOT. If DI seal leaks really could cause this, then I'm definitely willing to spend the money to fix it. I was just under the impression that when those seals fail, your engine runs way worse/not at all.

Another symptom I experience sometimes: I'll be in first, around 1k RPM or so, lightly hit the throttle, and nothing will happen for about a second, and then the car jerks to life and starts accelerating. That's a fun one. Also this morning my car really didn't want to start. Turned and turned for about 4 seconds before I tried again with the gas pedal to the floor. Then it started up. Leaky DI seal == gas chilling in cylinders on cold start maybe?

[Sportsguy83]

Originally Posted by neutral

Would DI injector leak cause this sort of semi-random crap though? My tuner said that they use DI until they need PI, so it makes sense to me why light throttle shows the issue way more than WOT. If DI seal leaks really could cause this, then I'm definitely willing to spend the money to fix it. I was just under the impression that when those seals fail, your engine runs way worse/not at all.

There are other symptoms you can check for DI seal injector leaks before spending money on it. Search on the forum and there are videos with the firecracker sound the engine makes when DI seals are shot.

[neutral]

Originally Posted by Sportsguy83

There are other symptoms you can check for DI seal injector leaks before spending money on it. Search on the forum and there are videos with the firecracker sound the engine makes when DI seals are shot.

Yeah I don't have that, and I suspect the other people in this thread don't either.

[Xero-Limit]

There's a lot that goes into the tuning side that can play a role here. Some cars/setups are much worse than others with the idle fluctuations, but often you can hone it in with precision if you adjust things correctly. Increasing the MAF size/location will have a very significant impact on the values the ECU expects to see at idle. If the tune adjusts the scaling to such a degree that that those are outside of the expected range, you will see severe fluctuations and stalling. You can also get the same exact issue if you overcorrect.

AOS, improperly installed catch cans, loose hoses and all those mechanical things will cause issues, no doubt about that. But if you've exhausted those then that would be the next place to look.

[Ken@PTuning]

We've tune numerous FB kits at the shop with good results. We've seen various issues but have always been able to correct them and tune them completely. PM me and I can go over some things to try in detail if you'd like.

[Jhood]

Thanks for all the replies guys, I have been very busy the past few days, but I am going to rip out the AOS tomorrow after work to see if it helps any. It didn't show any signs of leaking though when checking the system. I am also looking into other shops on Long Island that I can bring the car to for one last hope of finding out what the issue is. Moto East, you guys are almost 4 hours from me as you are located in PA and I'm in NY so I don't know if that is possible for me to drive the car as is that far of a distance.

Here are some logs I promised - the first one is with the Delicious Tuning 'hybrid' map & was a terrible drive, and the last two are with Full Blown's basemap installed. The "highway cruising" one probably shows it the best, although it gets much worse.

FBM Highway Cruising Hesitation
FBM 1st-2nd-3rd Driving
DT Hybrid 2nd-3rd Gear Driving

[VitViper]

Originally Posted by neutral

Count me in as another guy running Full Blown's kit with nasty partial throttle hesitations/stumbles. Been running the kit for about 8 months with various degrees of hesitation/drivability. Idles fine. I've been through 2 different tuners now (Dynosty, Delicious) which obviously points to something being wonky with my setup. Here's a log of the stumble through partial-throttle acceleration: http://datazap.me/u/neutral/driving-...d?log=0&data=6

If what you're saying is true, and it's just the FPR that's causing my headache..... I can't even begin to describe how happy I'll be.

Would something like this be what I might need? http://www.fastscions.com/NRG-Adjust...B-xD-FR-S.aspx

Or do you have another part to recommend?

Thanks,
Jeremy

It's pretty clear from that log you have an issue with the tune.

[GsxrMe]

Um.... is it me or does the exhaust valves look like they are opening super early on the DT Hybrid?

[GsxrMe]

Um.... is it me or does the exhaust valves look like they are opening super early on the DT Hybrid?

[Jhood]

Originally Posted by GsxrMe

Um.... is it me or does the exhaust valves look like they are opening super early on the DT Hybrid?

Yea I'm not sure what the issue is with their tune and my car, but I actually became scared to drive it after they revised it every time due to how erratic the driving / stalling / hesitations & noises became.