Hesitation Under Boost - TriStateTuners.com :: Home of Tristate Auto Enthusiast

jkjersey · 02-10-2007, 06:37 PM

I am having issues with my GC8. I am still awaiting to hear back from Rallispec to see what they think could be wrong or to take a look at it.

The car has a JDM STI VI (EJ207) drivetrain swap in it along with the JDM STI ECU
When the temperature started to drop last month I noticed my car started to hesitate when I was going from a cruise to when I pressed on the throttle more to accelerate.

It sounds like a sputter. I then started using Lucas Octane Booster according to their directions. This masked or fixed the problem. I thought it was an octane issue with the winter blends of gas. Then yesterday it started acting up more and worse to the point that when I get in boost it sputters. I do not hear any pinging or metal on metal of which I assume detonation sounds like. On my Greddy E-01 I see the curve spike and dropout and not look smooth when it happens.

Now when the weather was warmer I took the car back to Rallispec right away after getting it back because I heard a fuel pump noise like an electric humming. I took it back to them and they said that it probably needs a new pump and they had a hard time sourcing a pump for my GC8 due to compatibility reasons. (Can someone let me know what pumps would work for my GC8). So they had to modify my existing one.

Do you think these symptoms could be a fuel pump issue or even a fuel filter one?

No variables changed I use the same gas from the same gas stations.. unless I got a bad batch?

When the car isn't under boost and I lightly and slowly accelerate it can get in revs fine and is smooth as butter.

Can fuel pumps fail partially? Or is it all or nothing? I did notice that when my car got to a 1/4 tank or below it ran much worse and the acceleration under boost got more jerky.

I am very troubled and would like this fixed asap because it is my daily driver any input would be appreciated.

The car never got tuned for 93 octane because Rallispec and others said it should be fine with running the stock JDM sti ecu because the ecu would just pull timing. I was kind of always perplexed why others werent insisting that it has to be tuned from the getgo with ECUTEK. I just hope major damage hasn't occured.

----------------------------------------------------------------

Impreza GC8 JDM STI VI conversion
05 MCS

Drop by my page @ http://www.myspace.com/jkjersey

IMPREZvWRX · 02-10-2007, 06:57 PM

Quote:

Originally Posted by jkjersey

When the car isn't under boost and I lightly and slowly accelerate it can get in revs fine and is smooth as butter.

Can fuel pumps fail partially? Or is it all or nothing? I did notice that when my car got to a 1/4 tank or below it ran much worse and the acceleration under boost got more jerky.

Yes, they can. My old WRX had a Walbro 255 in it that wouldn't maintain pressure under boost after about 2 years of flawless service. It took forever to troubleshoot because the car didn't have a fuel pressure gauge in it, and showed strange symptoms (same as yours) with no trouble codes. It would probably be cheaper and easier to swap the pump out than to add a FP gauge at this point. Plus, you'd have a fresh pump either way.

jkjersey · 02-13-2007, 09:20 PM

Ok thanks Chris. Rallispec hasn't got back to me yet. I would like them to install the new pump since I paid mucho $$$ in labor for them to do the conversion. In the mean time I am driving it accelerating very gently.

Are there any other reputable places besides XoticMotorsports that could install a fuel pump for me and hook up a fuel pressure gauge? Xotic hasn't gotten back to me either I guess they are tied up or closed temporarily.
----------------------------------------------------------------

Impreza GC8 JDM STI VI conversion
05 MCS

Drop by my page @ http://www.myspace.com/jkjersey

IMPREZvWRX · 02-13-2007, 09:26 PM

When are you free? I'm down to 1 hand, but if you don't mind getting your hands dirty, we'll have the pump in quick...an hour, tops. Maybe Ralph would be up for it. Just gotta get my junker out of the garage first.

02-10-2007, 06:37 PM	#1
jkjersey Tri-State Training Wheels Join Date: Dec 2005 Location: South Jersey Member #1148 iTrader: (0)	Hesitation Under Boost I am having issues with my GC8. I am still awaiting to hear back from Rallispec to see what they think could be wrong or to take a look at it. The car has a JDM STI VI (EJ207) drivetrain swap in it along with the JDM STI ECU When the temperature started to drop last month I noticed my car started to hesitate when I was going from a cruise to when I pressed on the throttle more to accelerate. It sounds like a sputter. I then started using Lucas Octane Booster according to their directions. This masked or fixed the problem. I thought it was an octane issue with the winter blends of gas. Then yesterday it started acting up more and worse to the point that when I get in boost it sputters. I do not hear any pinging or metal on metal of which I assume detonation sounds like. On my Greddy E-01 I see the curve spike and dropout and not look smooth when it happens. Now when the weather was warmer I took the car back to Rallispec right away after getting it back because I heard a fuel pump noise like an electric humming. I took it back to them and they said that it probably needs a new pump and they had a hard time sourcing a pump for my GC8 due to compatibility reasons. (Can someone let me know what pumps would work for my GC8). So they had to modify my existing one. Do you think these symptoms could be a fuel pump issue or even a fuel filter one? No variables changed I use the same gas from the same gas stations.. unless I got a bad batch? When the car isn't under boost and I lightly and slowly accelerate it can get in revs fine and is smooth as butter. Can fuel pumps fail partially? Or is it all or nothing? I did notice that when my car got to a 1/4 tank or below it ran much worse and the acceleration under boost got more jerky. I am very troubled and would like this fixed asap because it is my daily driver any input would be appreciated. The car never got tuned for 93 octane because Rallispec and others said it should be fine with running the stock JDM sti ecu because the ecu would just pull timing. I was kind of always perplexed why others werent insisting that it has to be tuned from the getgo with ECUTEK. I just hope major damage hasn't occured. ---------------------------------------------------------------- Impreza GC8 JDM STI VI conversion 05 MCS Drop by my page @ http://www.myspace.com/jkjersey Last edited by jkjersey; 02-10-2007 at 06:49 PM.

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02-13-2007, 09:20 PM	#3
jkjersey Tri-State Training Wheels Join Date: Dec 2005 Location: South Jersey Member #1148 iTrader: (0)	Ok thanks Chris. Rallispec hasn't got back to me yet. I would like them to install the new pump since I paid mucho $$$ in labor for them to do the conversion. In the mean time I am driving it accelerating very gently. Are there any other reputable places besides XoticMotorsports that could install a fuel pump for me and hook up a fuel pressure gauge? Xotic hasn't gotten back to me either I guess they are tied up or closed temporarily. ---------------------------------------------------------------- Impreza GC8 JDM STI VI conversion 05 MCS Drop by my page @ http://www.myspace.com/jkjersey

02-13-2007, 09:26 PM	#4
IMPREZvWRX Tri-State Post Whore Join Date: Feb 2005 Member #164 iTrader: (3)	When are you free? I'm down to 1 hand, but if you don't mind getting your hands dirty, we'll have the pump in quick...an hour, tops. Maybe Ralph would be up for it. Just gotta get my junker out of the garage first.