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Old 11-25-2015, 04:40 PM   #1
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Question Hesitation Under Partial Throttle!

Hey guys, sorry for the long post, but once again another sad thread by me trying to figure out what the hell is wrong with my car. I have made the decision to finally sell the car this winter / next spring, it's just too much of a headache mixed with bad experiences from the aftermarket companies & shops. The thing is I'd like to finally get it running properly with this FI setup. Otherwise I will have to remove every aftermarket part off the car and sell them individually after I just trade the stock car in for KBB value. I'm currently running the entire FBM stage 1 kit (Bosch 550cc injectors, FBM 270 pump) with the GTX 28 turbo open dump, FBM radiator, Crawford AOS with check valves and vented back into the turbo intake. Gauges & BOV are connected to a vacuum distribution block that's tapped into the brake booster line. The wastegate is then tapped into the silicone coupler right after the turbo using an ATP Turbo-Tap. Currently running the FBM basemap at 7psi, with some revisions done by LJ.

The issue is that when it is warm the cars idle fluctuates from 750-1300 at stop lights (not always though). Pulling off in 1st gear is like I'm continuously applying and removing my foot from the gas pedal, it gets pretty bad. 2nd gear and up smooths out, but my AFR gauge is all over the place and I can feel the hesitation if partial throttle or just cruising along. The instant I slam the pedal down to WOT, the AFR stays pinned at 11-11.5, boost spools up smoothly and the car rips down the road just fine.

The car has never once ran right since I installed the FBM stg 1 kit. Yes, the installation is correct, I had No Limit Motorsports check over every inch of it after I installed it. It's been vacuum leak and boost leak tested by them and again by myself. The fuel pump has been removed and O-rings changed out multiple times. I dealt with the never ending exhaust leak problem due to the kits downpipe & manifold having bent flanges, along with the 3 other replacements that were sent until we got it together completely, but now it is good. I was told by No Limit that the tune was the reason for the hesitation in the car. LJ did many revisions for me and got it driveable, but the hesitation is still there. So I bought Delicious Tuning's Flash & Go tune, only to then not even be able to drive the car with it installed. DT responded by telling me that 100% there is a mechanical issue with the car, possibly a direct injection issue? Asked them twice how to find out for sure & I never received an answer back.

So now we have 1 tuner saying the logs look completely normal, the other tuner saying it's mechanical, and my shop saying it's absolutely the tune. So basically I might as well have taken the $10,000+ I've spent and shoved it up my ass.

In all seriousness, I'm willing to test any theories out. Please chime in with any help you can offer, I appreciate it. I will upload a few logs tonight if it helps.


*Added logs =
The first one seems to show it best

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

.
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Last edited by Jhood; 12-06-2015 at 01:12 PM.
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Old 11-25-2015, 04:45 PM   #2
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I have checked so far...

-Boost/vacuum leak tested
-Added extra cable from negative terminal to ground out DI ECU Module
-Fuel Pump O-rings added
-Checked all MAF/MAP wires and cleaned off MAF sensor
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Old 11-25-2015, 05:15 PM   #3
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have yiou checked for exhaust leaks before the O2 sensor?

as any air pulled in here will fool the sensor into adding fuel where its not required
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Old 11-25-2015, 05:27 PM   #4
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Can you post your log?
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Old 11-25-2015, 09:02 PM   #5
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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.

Last edited by aaguirre123; 11-25-2015 at 10:00 PM. Reason: add more comments and correct some comments
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Old 11-25-2015, 09:53 PM   #6
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Im having the same exact issue and ive tried just about everything you can think of.
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Old 11-25-2015, 11:02 PM   #7
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Ya post log....

You're missing and overlooking something. Bring the car to a professional and he'll make sure everything is installed correctly. If you have the slightest exhaust/boost/vacuum leak the cars sensors are going to make the car like shit.
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Old 11-27-2015, 10:59 AM   #8
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My advice is remove and sell that Crawford AOS. Run the crankcase vent tubes to a vented catch can and plug the intake manifold and intake. Then go take your car to Moto-East for a proper in person street and dyno tune. Get your money back from DT. Get the car running properly with a good tune and great dyno numbers. Enjoy the car for a month, see if you still want to sell. If you do want to sell, then now at least you can prove the car is running right and is making good numbers and it will increase your selling price. I have given the same advice to @Frs300 .
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Old 11-27-2015, 08:38 PM   #9
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Quote:
Originally Posted by King Tut View Post
My advice is remove and sell that Crawford AOS. Run the crankcase vent tubes to a vented catch can and plug the intake manifold and intake. Then go take your car to Moto-East for a proper in person street and dyno tune. Get your money back from DT. Get the car running properly with a good tune and great dyno numbers. Enjoy the car for a month, see if you still want to sell. If you do want to sell, then now at least you can prove the car is running right and is making good numbers and it will increase your selling price. I have given the same advice to @Frs300 .
we both have the crawford aos if that says anything.

no tuners close to here or i would have been good by now lol
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Old 11-28-2015, 07:52 PM   #10
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Quote:
Originally Posted by aaguirre123 View Post
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.
Is there way to test the Evap solenoid to confirm if it is functioning correctly or leaking?
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Old 11-28-2015, 09:01 PM   #11
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Sure uninstall apply 12v then blow air thru it
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Old 11-29-2015, 04:06 AM   #12
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Originally Posted by Frs300 View Post
we both have the crawford aos if that says anything.

no tuners close to here or i would have been good by now lol
Jamesm/James Martin/HRI Tuning. Remote Tuning. The guy painstakenly spent nearly 5 MONTHS dedicated to perfecting my street tune. Mostly due to my repeated errors and trying out different setups. He has been the only tuner that has made sure my car was good on all daily conditions and not just the dyno runs.

One of the things we found was slight turbulance caused by the soft coupler hening the passenger headlight. Under partial throttle/light roll ons or keeping the throttle low enough where we were cruising at 0psi the turbulance with the slightest increase of boost would cause the MAF to go weird causing all kinds of hesitations and inconsistancies. After having him redo months of tuning he suggested speed density which completly cured this issue when we got it finished up. Can't speak highly enough of the poor bastard.

PS he's also offering $100 off rightnow via his facebook on his $400 tunes.
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Old 11-29-2015, 12:10 PM   #13
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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
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Old 11-29-2015, 12:29 PM   #14
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Quote:
Originally Posted by Jhood View Post
The issue is that when it is warm the cars idle fluctuates from 750-1300 at stop lights (not always though). Pulling off in 1st gear is like I'm continuously applying and removing my foot from the gas pedal, it gets pretty bad. 2nd gear and up smooths out, but my AFR gauge is all over the place and I can feel the hesitation if partial throttle or just cruising along. The instant I slam the pedal down to WOT, the AFR stays pinned at 11-11.5, boost spools up smoothly and the car rips down the road just fine.
Sounds a lot like my car before a rod let go. Hope you get it fixed soon.
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