Need some help diagnosing this. Fuel Cut?

[Kiske]

Hi guys, this has recently started happening the past 3 days and has made my BRZ undrivable without risk of getting stranded on the side of the road.

The issue started as a slight hesitation, then became a feeling similar to hitting a fuel cutoff/rev limiter. It happens under all driving conditions (light & partial throttle, wot.) It very rarely happens at idle, or is masked well enough I cannot tell. Car has been running fine for the majority of the year otherwise. It seems to happen in closed loop (warmed up) way more frequently. In fact the first 10min of driving are problem free. After a good half hour daily commute the car violently bucks and jerks. After this has happened enough eventually the car will stall if not moving. After it gets to this point it becomes very difficult to restart until it has cooled or sat for a bit. Then the issue repeats. The exhaust smells pretty rich despite fuel trims not being too far off.

Here is a video of the issue. In the video the car is warm and being held around 3100rpms with a steady pedal. As you can see it cuts out, dips, stumbles and catches itself just as I let off the throttle. (trying to prevent it from stalling.)
https://www.facebook.com/847745593/v...7785091455594/



After the vehicle settles back down and idles in the video, I tried my best to quickly get a snap shot of what everything was reading.

I've been trying to log the even with ecutek but, the stalling and bucking keeps messing up the connection kicking me out of map access.

[humfrz]

Originally Posted by Kiske

Hi guys, this has recently started happening the past 3 days and has made my BRZ undrivable without risk of getting stranded on the side of the road.

DANG, Kiske, you have been around long enough to know we need more information ........

Miles on your car .. ??

Under warranty .. ??

Power mods .. ??

Do you track it hard .. ??

Aftermarket tune .. ??

Is it giving you a code(s) ..... if so, what .. ??





humfrz

[Ultramaroon]

If it eventually stalls while idling I bet if you log engine parameters while that happens, we'll be able to see something.

Also, it's surprising that it hasn't thrown any codes.
@humfrz, he has it all in his build thread. FBM Turbo kit.

[Tcoat]

In the old days I would say clogged fuel filter in a heart beat. Hell I am still going to say that! I have zero clue about what all the numbers mean but your description is a clogged filter to a tee. Clogs up sucking fuel and then clears it self once suction is stopped. Rinse and repeat.
Ok at idle since the demand is low. Check
Can be unpredictable but usually happens after running a certain period of time. Check
Cough, sputters and stalls. Check
Trims look ok (will take your word on that one) Check
Doesn't trigger a CEL. Check
Smell rich (just before running out of fuel there is not the proper mix and ironically the car will run rich before stalling because not enough gas) Check

[Ultramaroon]

Originally Posted by Tcoat

In the old days I would say clogged fuel filter in a heart beat. Hell I am still going to say that! I have zero clue about what all the numbers mean but your description is a clogged filter to a tee. Clogs up sucking fuel and then clears it self once suction is stopped. Rinse and repeat.
Ok at idle since the demand is low. Check
Can be unpredictable but usually happens after running a certain period of time. Check
Cough, sputters and stalls. Check
Trims look ok (will take your word on that one) Check
Doesn't trigger a CEL. Check
Smell rich (just before running out of fuel there is not the proper mix and ironically the car will run rich before stalling because not enough gas) Check

Hmmmm.... Except it stalls at idle.

[Tcoat]

Originally Posted by Ultramaroon

Hmmmm.... Except it stalls at idle.

"Very rarely"

[Ultramaroon]

Originally Posted by Tcoat

"Very rarely"

I like it.

[Kiske]

Originally Posted by humfrz

DANG, Kiske, you have been around long enough to know we need more information ........ humfrz

Miles on your car .. 30,xxx boosted since 2,000mi

Under warranty .. lol though I do sometimes fantisize about demoding and passing the car off as 'lightly driven' :P

Power mods .. yup, nothing changed recently though. Just reliability mods, maintance and suspension work this year

Do you track it hard .. not in a year or so. cars been needing everything under the sun before it will see track again.

Aftermarket tune .. yes, hri/jamesm. Has been running fantastic since turbo installation

Is it giving you a code(s) ..... if so, what .. zero dtc, nothing pending either. This is bothering me most because I'd think surely if the car is fucking up bad enough to stall and be undrivable I'd get something at least to narrorw down my search. I've tried to drive it safely as much as I can since the issue showed up trying to get a cel to pop on and nothing.

Originally Posted by Ultramaroon

If it eventually stalls while idling I bet if you log engine parameters while that happens, we'll be able to see something.

Like I said, I can't really log the event because when it the bucking happens and I stall I it boots me out of map access and kills the log file. Instead of saving it until the car dies.
I'll keep trying though.

Originally Posted by Tcoat

In the old days I would say clogged fuel filter in a heart beat. Hell I am still going to say that!

I've already peeked at the filter in the tank. Best think about this car is how easy it is to pull the seat cushion to get to the pump. Sock still looks brand new.

Originally Posted by Tcoat

"Very rarely"

Correct, the only time it will stall at idle is after it has been bucking for a while and I've been driving it a good half hour. When I first cold start it, it is perfect until changing over to closed loop after a good 5-10 min of operation. Because of this I started checking the maf, o2 and intake/exhaust for leaks. Even swapped the sensors with new ones.

[Tcoat]

Well that should rule the filter out then.

[humfrz]

Maybe the crickets all died .......thus, the HPFP is not working too good ...... ??


humfrz

[Kiske]

Finally managed some logs. Ecutek cord is crapped out on me.

Large file is me slowly taking the car to 3k then back to idle a few times. In this file everything seems happy except fuel trims at idle. The car isn't bucking or wanting to die in this log.

The small file is the car at it's worst. Me just trying to keep the car alive before it stalls. I'm holding the throttle open at around 30% the best I can and the cars bouncing around mad.

http://www.filehosting.org/file/deta.../kiskelogs.zip

[humfrz]

Have you checked the fuel pressure at the fuel rail ......??


humfrz

[Ultramaroon]

Originally Posted by humfrz

Have you checked the fuel pressure at the fuel rail ......??


humfrz

That's logged.

[Kiske]

I let the car sit a couple hours and restarted it, letting it idle 3-4min before this log. At the beginning of the log you can see the car idling, I then slowly rev the car up to 2500rpms and it does a cutout before returning to 2500 and then I let off the throttle ending the log.

http://s000.tinyupload.com/index.php...24056653087890