Major bogging and hesitation when giving throttle - Subaru WRX Forum
Reply
 
LinkBack Thread Tools Display Modes
#1 Old 06-01-2011, 12:22 AM
WRXtuners Member
 
Join Date: Jun 2011
Location: Oregon
Posts: 8
2002wrxpdx is an unknown
Major bogging and hesitation when giving throttle

I have been over all sorts of stuff and I am finally going to post on here and see what feedback you guys might have.
Car: 2002 WRX, 2.5L Sti block, 2.0L heads, stock head gaskets, 900cc injectors, aftermarket fuel rail and regulator (same pressure as stock), VF39 turbo at 15psi, silicone turbo intake tube, short ram intake, AEM cone filter, large billet MAF housing, TGV deletes, custom reflash tune, brand new Walbro 255 pump, brand new fuel filter, brand new Oxygen sensor, brand new OEM ignition coils, good plugs gapped at .028", full catless up/downpipes, 3" exhaust.

Ever since I got the car it has idled poorly, but always ran fine once off of idle. In the process of diagnosing the bad idle, I replace several parts (coils, O2 sensor, etc).
But recently, it has developed a terrible bog when I give it any sort of throttle. major hesitation, and often some popping from the intake (mini back-fires). This has gotten worse over the last week or so, the car is now hardly driveable.

Here is what i have checked:
1. replaced the MAF with a known good MAF
2. replaced the MAP sensor with a known good one
3. checked plugs (tips are clean, no fouling, they look descent).
4. pressure tested inductions system for major leaks, etc, nothing.
5. Cleaned both MAF's with sensor cleaner, re-tried both of them.
6. Flow tested injectors, all flowing at 900cc (de-capped stock injectors) at 3Bar.
7. Installed a fuel pressure gauge, shows exactly specified fuel pressure (3 bar).

Just today I installed a new Walbro fuel pump, problem did not change.
I am not getting any smoke out the tail pipe.

No engine codes (I have the evap, TGV and secondary O2 DTC's turned off).
The only damn thing I have not checked is the throttle position sensor. But I will need to borrow a live-data scan tool to check it, I will do that in a few days.
Any other ideas of what to try???? It is killing me!
2002wrxpdx is offline  
Sponsored Links
Advertisement
 
#2 Old 06-01-2011, 07:42 AM
WRXtuners Member
 
bad grocerygetter's Avatar
 
Join Date: May 2010
Location: Oklahoma
Posts: 453
Images: 2
bad grocerygetter is a helpful contributing member
Prob goes without saying but the car is tuned right??

Kevin.
Cobb ap stage 2 ots, catless uppipe, catless turboback, Cobb Sf intake.
bad grocerygetter is offline  
#3 Old 06-01-2011, 08:52 AM
WRXtuners Member
 
Join Date: Jun 2011
Location: Oregon
Posts: 8
2002wrxpdx is an unknown
Yes, the custom reflash tune is in there. Like I said this bogging is relatively new and has gotten gradually worse over the last week.
2002wrxpdx is offline  
#4 Old 06-01-2011, 09:47 AM
WRXtuners Member
 
bad grocerygetter's Avatar
 
Join Date: May 2010
Location: Oklahoma
Posts: 453
Images: 2
bad grocerygetter is a helpful contributing member
Hmm. Anyway to do a compression and or leakdown on it?

Kevin.
Cobb ap stage 2 ots, catless uppipe, catless turboback, Cobb Sf intake.
bad grocerygetter is offline  
#5 Old 06-01-2011, 10:41 AM
WRXtuners Member
 
Join Date: Jun 2007
Location: Texas
Posts: 4,970
pzr2874 is known to be trustworthy and helpful pzr2874 is known to be trustworthy and helpful
You clean or replace the IACV lately?

Paul
2007 XT
2007 MS3
pzr2874 is offline  
#6 Old 06-01-2011, 11:32 AM
WRXtuners Member
 
Join Date: Jun 2011
Location: Oregon
Posts: 8
2002wrxpdx is an unknown
Did a compression test about a month ago, all was good, since then I have not beat on it at idles.
it starts and idles fine (well, idle has always been somewhat shaky, but for now it seems good.)
i can't give it more than 10% throttle or it lurches, bogsand bucks.it is either pulling timing or getting inaccurate inputs from maf or tps.this sucks.
i about to take it to a shop....which I hate doing.
2002wrxpdx is offline  
#7 Old 06-01-2011, 12:26 PM
WRXtuners Member
 
Join Date: Jun 2007
Location: Texas
Posts: 4,970
pzr2874 is known to be trustworthy and helpful pzr2874 is known to be trustworthy and helpful
Couple buddies of mine had similar issues that you have and it was 2 different issues, one was the IACV and the other was one injector that had the wiring backwards (DW believe it or not).

You have a way to datalog or monitor anything?

Paul
2007 XT
2007 MS3
pzr2874 is offline  
#8 Old 06-01-2011, 04:12 PM
WRXtuners Member
 
Join Date: Jun 2011
Location: Oregon
Posts: 8
2002wrxpdx is an unknown
Isnt idle irrelevant when I am into the throttle? And it idles pretty well too.
Also, since injecors are just solenoids, they dont have polarity.
I honestly do appreciate all the input. Sometimes a suggestion can lead to a solution , even if the suggestion itself is not the solution..
2002wrxpdx is offline  
#9 Old 06-01-2011, 09:44 PM
WRXtuners Member
 
BLAZE2099's Avatar
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 2,574
Images: 6
BLAZE2099 is known to be trustworthy and helpful BLAZE2099 is known to be trustworthy and helpful
Quote:
Originally Posted by pzr2874 View Post
You clean or replace the IACV lately?
get a new gasket for it and try it, this sounds to be your cause as I was thinking the same thing while reading your list of things done to try and solve.
pretty sure that unabomber over on nasioc has a how to for this as well, maybe its in his manifesto?....GL

....................CHEERS!!!

Randy-
2002 blaze WRX- sold:(
2004 Wrx-sold
2011 Wrx limited
99 Fozz- sold
Eagle eye crew
BLAZE2099 is offline  
#10 Old 06-01-2011, 09:46 PM
WRXtuners Member
 
BLAZE2099's Avatar
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 2,574
Images: 6
BLAZE2099 is known to be trustworthy and helpful BLAZE2099 is known to be trustworthy and helpful
oh, and did you check your BPV for leaks?, that would give you those same exact symptoms.

I know you stated you checked for leaks, but that just sounds too dead on.

Randy-
2002 blaze WRX- sold:(
2004 Wrx-sold
2011 Wrx limited
99 Fozz- sold
Eagle eye crew
BLAZE2099 is offline  
#11 Old 06-02-2011, 05:51 AM
WRXtuners Member
 
Join Date: Jun 2007
Location: Texas
Posts: 4,970
pzr2874 is known to be trustworthy and helpful pzr2874 is known to be trustworthy and helpful
Quote:
Originally Posted by 2002wrxpdx View Post
Isnt idle irrelevant when I am into the throttle? And it idles pretty well too.
Also, since injecors are just solenoids, they dont have polarity.
I honestly do appreciate all the input. Sometimes a suggestion can lead to a solution , even if the suggestion itself is not the solution..
It was something "backwards" on it... Maybe the pins. Engine rocked like it had no motor mounts but acceleration was "ok" till the gas was released and afterfired like a MF.

Not to be a stickler, but who did the pump install? Did you play with the intake manifold or the fuel lines at all ?

Paul
2007 XT
2007 MS3
pzr2874 is offline  
#12 Old 06-02-2011, 11:45 AM
WRXtuners Member
 
Join Date: Jun 2011
Location: Oregon
Posts: 8
2002wrxpdx is an unknown
I have cleaned the idle valve, back when I was diagnosing a poor idle a month or so ago. I reinstalled with a brand-new idle valve gasket from the dealer.

I installed the pump a few days ago as an effort to diagnose the surging/stumbling/seizure it has.
It did not effect the problem (not better, not worse). But It was good because I wanted a Walbro in there anyway, and this gave me an excuse to get it done.

Yes I have had the intake manifold off, reinstalled with all new gaskets, same problem. The fuel rails are plumbed up with -6AN hose and fittings.

As for the BPV, it is recirculating back to the turbo inlet tube (as it should be).
Here is how I check for leaks:
I take off the cone air filter from the intake and put a plastic cap with an air fitting into the coupler and tighten the coupler clamp down.
I dial down my air compressor to 15 psi and hook it up to the fitting on the intake. Then I listen and look for leaks. I also spray questionable areas with soapy water and look for bubbles. This method works pretty well, I can hear even the smallest leaks. It is all solid and leak free.

Last night I pulled out all the injectors. In the #1, there were some very small metal chips in the inlet on the injector. Luckily each injector has a small screen on the inlet, this is where the chips were. Maybe this is from the IXIZ Concept fuel rails. I cleaned it all out blew air through the injector while activating it with a battery and reinstalled all the injectors (I cleaned all of them out). I also celaned out the fuel rails and lines, but nothing came out of them.
I also swapped in my other MAF sensor, just for the hell of it. I have been alternating between the 2, but usually it doesnt help.

The first couple minutes of a test drive and it seemed better. Then as I got down the road a mile or two, it all came back. I swore out loud and wanted to drive off a cliff.

Here is the deal, it is pretty much OK up to 2500RPM, then it bucks violently and stumbles, I can rev through it and stops bucking at 3500RPM. I dont want to rev it up becuase of this problem, so I am stuck driving around under 2500RPM.

$25 Paypal to anyone who solves this!
2002wrxpdx is offline  
#13 Old 06-02-2011, 11:54 AM
WRXtuners Member
 
Join Date: Jun 2007
Location: Texas
Posts: 4,970
pzr2874 is known to be trustworthy and helpful pzr2874 is known to be trustworthy and helpful
AHHAHAA... ^^ Better be no fees... j/k

Did you have the issue B4 the fuel rails went in ?

Another question... I like Ming as much as the next person.... But why did you get new rails ? Are you running a Garrett 40R ?

Just an idea but put the stock rails back on and see if it does it...

Paul
2007 XT
2007 MS3
pzr2874 is offline  
#14 Old 06-02-2011, 01:43 PM
WRXtuners Member
 
Join Date: Jun 2011
Location: Oregon
Posts: 8
2002wrxpdx is an unknown
Quote:
Originally Posted by pzr2874 View Post
AHHAHAA... ^^ Better be no fees... j/k

Did you have the issue B4 the fuel rails went in ?

Another question... I like Ming as much as the next person.... But why did you get new rails ? Are you running a Garrett 40R ?

Just an idea but put the stock rails back on and see if it does it...
I got new rails because I was swapping injectors in and out diagnosing the bad idle, The stock rails made it a pain in the ass. Way easier to pull ou the injectors with these rails. Also, my stock fuel rails were rusted all over the outside, and the regulator was all seriously rusty too. this used to be an east coast car.
The stock rails were corroded so bad, one of the mouting tabs broke off. They are long gone in the trash.

Yes, it has run fine with the new fuel rails and regulator. I am running the exact same fuel pressure as stock. I checked before and after the install.
2002wrxpdx is offline  
#15 Old 06-02-2011, 07:06 PM
WRXtuners Member
 
Join Date: Jun 2011
Location: Oregon
Posts: 8
2002wrxpdx is an unknown
Here is a new clue. I borrowed an OBD2 scan tool that lets me watch live data. During the bogging/bucking event short term fuel trims shoot up to +25% which means the computer is trying desparately to add fuel. So I am thinking it is a fuel delivery problem.
I am going to take it all apart tonight and test everything.

I have another set of injectors to put in, but they are 600cc. I am currently tuned for 900cc. ANyone know how to rescale injectors with ECU Flash software?
thanks
2002wrxpdx is offline  
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On