The famous stumble...fixed?

Fuel filter or pump changed recently? Mine is still present as well but not as pronounced as before. First mod was the fpr (ran good for a week until the ecu learned it back)

Second was spark plugs (previous owner had Tribeca plugs in it )

Then fuel pump and filter (running great but still little hiccups here and there)

Need to tee the bpv line and see how that does. . .

 

DW65c just put in.

 

Tried zero'ing individual ipw comp tables and logging? I think that might be part of my problem; real life fueling no longer matches with stock ipw comp tables. Not that i know much about what i'm talking about.

 

Sent from my XT1028

 

Tune has not been adjusted for the fpr mod. I read earlier in the thread that Dave from cryotune said it was not necessary, he is my tuner.

 

Edit: SBT mentioned something about worn half shafts and I've got another opinion that its driveline lash. The more I read about driveline lash the more I think that is it and is related to something going on down there. I'll start looking in that direction.

Edited July 18, 2015 by xtea

Is it normal to feel a subtle tapping or pulse in the top fuel line, the one not connected to the 07 fpr? The line connected to the fpr does not have the tap or pulse feeling on either side of the fpr. The top one does have that feeling.

Supply and return. Using a larger size hose can be dangerous. It tends to lead to leaks.

I extended the supply line about 3 ft and the hesitation is almost completely gone. I'll add length to the return next and see what the results are. I have not changed the regulator setup. Total spent so far is less than $25.

I extended the supply line about 3 ft and the hesitation is almost completely gone. I'll add length to the return next and see what the results are. I have not changed the regulator setup. Total spent so far is less than $25.

 

Is the supply line the too one or the bottom one going to the regulator?

Is the supply line the too one or the bottom one going to the regulator?

Honestly I'm not sure. I extended the top hose on the manifold. I planned to experiment first to see what worked and then trim my 3ft of hose. Lol

At least on mine, top is feed, bottom is return. The one with the regulator is the return either way. It only allows fuel to flow past if it's over the 43 psi or whatever it's supposed to be.

 

Sent from my XT1028

When I did the FPR mod I did not use 3 feet of hose on the supply line. I just replaced the hoses and installed the sti FPR. I am going to put 3 feet in on the supply line and see if that fixes it.

 

Even still I think my specific issue is mechanical as it seems to be worse when driving down hill. I am stil puzzled that it came out stronger after going stage 3. Is it possible that the stumble could exasperate driveline lash at specific rpms under light load? I am seeing the soft spot almost always at 2500 and sometimes also at 2300 and 2900 depending on how I am driving.

Well I elongated the supply hose to 4ft. I still have my low rpm stutter but I am fairly certain it is mechanical now. The soft spots at 2300, 2500, and 2900 seem all but gone since I elongated the hose. I could be intoxicated with hope and imagining the improvement but I think I am halfway there.

I hated the stumble i switched to topfeed so i eliminated it permanently without mercy and with out guessing, **** the dual fpr setup.

 

http://imageshack.com/a/img901/4205/ONWcRf.jpg

I hated the stumble i switched to topfeed so i eliminated it permanently without mercy and with out guessing, **** the dual fpr setup.

 

http://imageshack.com/a/img901/4205/ONWcRf.jpg

You're 05 so you had side feeds, you're saying when you switch to topfeed you're stumble stopped? What was aftermarket? Just the fuel pressure regulator?

You're 05 so you had side feeds, you're saying when you switch to topfeed you're stumble stopped? What was aftermarket? Just the fuel pressure regulator?

IAG fuel manifolds in the pic (and probably topfeed tgv deletes). I assume all the lines in the engine bay are new and routed differently too. Basically, his entire fueling system in the bay is aftermarket.

 

Sent from my XT1028

+1 as per Lance Lucas of COBB, he curses the sidefeed injector.

I have IAG TGV Deletes, fuel lines and rails with ID1000and Aero FPR, ready to go in.

I cant wait for smooth idle,and no more cold fuel smell...

Yup all new lines, rails, dampeners, tgv deletes, fpr, and it's routed in series 4-2-1-3 to the fpr.

Anyone here with an 08-09 done this?

Me, but didn't fix my issue, but i'm not on stock fueling.

 

I believe the stumbles i have are different.

 

Sent from my XT1028

Edited July 22, 2015 by Flinkly

my stumble was totally removed with custom tune. 08 top feed on stock fueling

also, as good of a place as any, I made a custom adapter for my stock 08 FPR location (I believe 07-09 LGT and OBXT, 08-14 WRX) to replace it with a different FPR, and have 5 extras (cost for 1 vs. 5 was insignificant). FPR location adapter on one side, stock hose sized barb on the other. re-use screws and o-ring from FPR. stainless barb section press fit into aluminum part.

Just installed the 05 STI FPR, here are some pics and feedback.

 

All of the crap on the left replaced with one small part.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_004.jpg~original

 

Went from this:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_001.jpg~original

 

To this:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_011.jpg~original

 

Still having a hard time finding a spot for the fuel filter, but with the stock FPR out of the way some room opened up for the filter.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_009.jpg~original

 

Also the head is not attached but is clamped on, I was able to carefully rotate it to eliminate any kinks in the vacuum line.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_010.jpg~original

 

 

As for the stumble, the hill that I would usually get it on (climbing at 2-2.5k rpm) seems just about fully eliminated, but that's on a fairly fresh ecu reset, I'll hold my judgement until I drive a bit more.

 

As for AFR's at WOT, they stayed roughly the same, a touch richer (within margin of error). Power gains were also within margin of error, nothing worth mention.

Edited July 24, 2015 by covertrussian

Just installed the 05 STI FPR, here are some pics and feedback.

 

All of the crap on the left replaced with one small part.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_004.jpg~original

 

Went from this:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_001.jpg~original

 

To this:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_011.jpg~original

 

Still having a hard time finding a spot for the fuel filter, but with the stock FPR out of the way some room opened up for the filter.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_009.jpg~original

 

Also the head is not attached but is clamped on, I was able to carefully rotate it to eliminate any kinks in the vacuum line.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_010.jpg~original

 

 

As for the stumble, the hill that I would usually get it on (climbing at 2-2.5k rpm) seems just about fully eliminated, but that's on a fairly fresh ecu reset, I'll hold my judgement until I drive a bit more.

 

As for AFR's at WOT, they stayed roughly the same, a touch richer (within margin of error). Power gains were also within margin of error, nothing worth mention.

 

What is the black thing in the feed line? How did you rotate the head of fpr?

What is the black thing in the feed line? How did you rotate the head of fpr?

 

Pre 05/06 Subaru's had them in the engine bay, then they moved them to the gas tank.

 

Rotated it very carefully with vice grips, didn't clamp it, just pushing on the vacuum rotated it.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/FPR/STI-FPR_006.jpg~original

Oh Snap thats the fuel filter! That is pretty smart to move it to the bay. I didn't think rotating the fpr head was safe. I'll give it a go. Right now my vacuum line is making a right angle.

Oh Snap thats the fuel filter! That is pretty smart to move it to the bay. I didn't think rotating the fpr head was safe. I'll give it a go. Right now my vacuum line is making a right angle.

 

I didn't want to pay $70 every couple years and dig in the fuel tank, thus I retrofitted the fuel filter in the engine bay and bypassed in-tank filter. Took a couple months of research and trial and error but so far it has been pretty solid.

 

It shouldn't hurt rotating it, but if you wanna wait a some time I'll report back if mine is still doing fine in a couple days.

Thanks for this Brian, definitely saved my stumble. There is mechanical chatter at idle, but it's worth it.

 

I also have 4 of the Doorman adapters, brand new, which I cannot return so if anyone wants some cheaper than Amazon, hit me up

Thanks for this Brian, definitely saved my stumble. There is mechanical chatter at idle, but it's worth it.

 

I also have 4 of the Doorman adapters, brand new, which I cannot return so if anyone wants some cheaper than Amazon, hit me up

 

Interested in the adapters, will send you a PM .

PM replied