Idling and flat spot issues on SC 2.5 - help needed!

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Idling and flat spot issues on SC 2.5 - help needed!

Postby Jiyujin » Mon Nov 07, 2016 1:48 pm

Hey all,

It's been a while since I've posted here due to illnesses and death in my family which have taken up most of my time.

I would like to ask some of you long-time experienced members for any help or assistance in solving this mystery.

To cut a long story short, I'm having ongoing idle bounce and flat spot or hesitation issues for a while now and can't seem to find what's causing these problems.
The car gets driven once or twice a week and barely does 10,000 kms a year. I put in Subaru injector cleaner once every 6 months and gets serviced 3 times a year.
It's a running a Raptor Supercharger (7psi boost) on a stock 2.5, and Omni 3 bar MAP sensor.
These problems are intermittent and would happen when the engine is cold or hot when accelerating from a stop.
On some hot or cold days the car would be perfect but on other days it would be a pain to drive.
I'm running 95 from my local BP and have been for the last 2 years since I've had the car.

What I have replaced in the past 12 months of the top of my head, there may be something that I've missed though...

1. New DW 65C fuel pump and in-tank filter.
2. New (3rd set) spark plugs.
3. New (2nd set) Pink Sti injectors.
4. New (3rd one) 02 oxygen sensor.
5. New Apexi air filter.
6. New BOV.
7. New (3rd one) MAF.
8. New SC belt.
9. New water reservoir.
10. New fuel pressure damper
11. Replaced ignition coil
12. Replaced throttle body

I'm out of ideas so any constructive advice is greatly appreciated!

Updates:
I've cleaned the throttle body several months ago but it made no difference.
I was told by my tuner that it is fuel related.
I have had it checked for vacuum leaks, no problem there.
I've installed another tested set of injectors (same flow rate) to check if they were the cause of the idle bounce, no change.
Last edited by Jiyujin on Thu Dec 15, 2016 8:24 am, edited 7 times in total.
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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Surge » Mon Nov 07, 2016 5:25 pm

Who tuned it?
DIY romraider E85 tuned Subaru liberty GT Premium 2010 Auto.
New project: Lexus Soarer 2.5gtt jzz30 1992

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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Jiyujin » Mon Nov 07, 2016 6:38 pm

Surge wrote:Who tuned it?


Hey Surge,

I would rather not say at this time as I'd like to focus on the problem.

Cheers mate!
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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Surge » Mon Nov 07, 2016 10:05 pm

Could it possibly be the wrong size O rings in the fuel pump assembly.
DIY romraider E85 tuned Subaru liberty GT Premium 2010 Auto.
New project: Lexus Soarer 2.5gtt jzz30 1992

[ACT]Free Tune help- Learning view, Romraider, ECU Flash
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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Jiyujin » Tue Nov 08, 2016 8:24 am

Surge wrote:Could it possibly be the wrong size O rings in the fuel pump assembly.


I used the supplied o-rings from DW, unless they gave me the wrong ones which I doubt very much. I may pull the fuel pump out and check that or replace it with a new one.
Do the AUDM have a FPR (Fuel Pressure Regulator ) that controls the fuel pressure in the engine bay?

Cheers Surge.
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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Surge » Tue Nov 08, 2016 12:58 pm

Out6ack wrote:**Additional info on CRITICAL o-ring sizes and placement.**
(Copied from E85 H6 = WINNING thread.)

Out6ack wrote:This was bugging me so I removed the DW65 tonight to triple check everything. I also had my laptop handy to display a bloody good downloaded workshop manual that I'd recently bought online -opened at the fuel pump page.
I noticed something within this manual's guide that I hadn't seen mentioned in either Club Lib's or NASIOC's walk through on the subject -both of which I solely referred to for my guidance during initial install.

The 4 o-rings are 2 different sizes (2X7mm + 2X8mm internal diameter) and MUST be installed to their correct locations or you might suffer pressure retention issues ..like I did.

I'm not to proud to raise my hand and say 'I Phukked Up!' in this instance.

I had overlooked the 1mm diameter difference between these o-rings and didn't have them located in their correct position. The walkthroughs I mentioned were very helpful and excellent guidance, but please be aware for future reference that this critical o-ring diameter and placement location is not mentioned in either guide.

So here tis..

Place a 7mm ring on the BLACK connector.
Place an 8mm ring on the WHITE connector.
image.jpg



Place an 8mm ring on the DW65c pump. (This is where you can put the additional 2nd ring.)
Align the 4 slots on the pump spacer sleeve with the 4 ribs within the basket. (Well, I did anyway..)
image.jpg




Place 7mm ring on lower BLACK connector that feeds to the base of the basket.
image.jpg



Done.

And umm yeah, priming problem tested ...and confirmed SOLVED.
Starts up quickly whether primed or not.

**I can only speak of my own findings, but strongly suggest to anyone having priming/starting/pressure issues to quickly check the correct placement of these o-rings.**

I'll be the one in the corner with a Dunce hat on.. :roll:


Jay.

DIY romraider E85 tuned Subaru liberty GT Premium 2010 Auto.
New project: Lexus Soarer 2.5gtt jzz30 1992

[ACT]Free Tune help- Learning view, Romraider, ECU Flash
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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Surge » Tue Nov 08, 2016 1:00 pm

Would be worth checking o-rings as per above.

Also some people use a double o ring on the pump nozzle.

Lastly the fpr should be in this location (obviously turbo model in pic but location should be the same):
https://encrypted-tbn0.gstatic.com/imag ... tJ2vtJFyMw
DIY romraider E85 tuned Subaru liberty GT Premium 2010 Auto.
New project: Lexus Soarer 2.5gtt jzz30 1992

[ACT]Free Tune help- Learning view, Romraider, ECU Flash
User avatar
Surge
 
Posts: 807
Joined: Sat Dec 08, 2012 1:28 pm
Location: ACT
Car: 2010 lib GT premium + Jzz30 soarer

Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Jiyujin » Tue Nov 08, 2016 2:53 pm

Surge wrote:Would be worth checking o-rings as per above.

Also some people use a double o ring on the pump nozzle.

Lastly the fpr should be in this location (obviously turbo model in pic but location should be the same):
https://encrypted-tbn0.gstatic.com/imag ... tJ2vtJFyMw



Hey Surge,

Appreciate the information and will replace the fuel pump and frp and see how she goes.
Hopefully it'll fix the problem. It drove terribly today, missing and hesitating when taking off.

Cheers mate!
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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Jiyujin » Thu Nov 24, 2016 4:32 pm

Just a quick update. Have replaced the fuel pressure damper and it made a slight difference. There is still an idle bounce during the warm up stage and also hesitation once the engine is at running temperature.
Am at a loss what to do next.... :?: :?:
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Re: Idling and flat spot issues on SC 2.5 - help needed!

Postby Jiyujin » Thu Dec 15, 2016 8:20 am

Update: It seems that the ignition coil was the source of the flat spot / hesitation when accelerating. After replacing it, the problem seems to have gone.
There is still an idle bounce during the warm up stage and at running temperature.
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