HELP! - Flat Spot

[brwnboy]

Hey Team really appreciate some help here! ???!

Almost ready to take the car in but wondering if i could have a hand prior to spending too much money at the mechanics! However i am happy to spend money on new sensors etc to update the ol girl.

OK so i have a 98 V4 GF8 Wagon, Have upgraded a few parts to V3 STi as follows, VF23 Turbo, Yellow Top Injectors, Orange Air Flow Meter, 6S STi RA ECU. A few bits in bobs to keep me interested till more funds are available.

So once i installed everything i had a hesitation flat spot and wasnt able to reach 1 bar of boost, i have a Blitz dual boost gauge/ turbo timer but it reads in kg/cm2 currently hitting 0.84kg/cm2 using online converter comes to 0.82bar, correct me if im wrong. I have been told the V3 STi will run 1Bar no probs...

So while i was changing parts I decided to change my spark plugs and leads, swapped to some Bosch Fusion Iridiums and Bosch Super Leads. Once i changed those still had hesitation- almost had enough then read up about the green and black plugs!!! So found out i had error code 32 - O2 Sensor, got a new Bosch Universal Sensor plugged it up and car felt a lot smoother, at the same time did the ol Upper Engine Cleaner again much better idle, took her for a run and still hesitation!! At this point i thought ok it must be a vac leak so bought myself a heap of flextech hosing and changed as much as i could..

So took advice from the site and got myself a new AFM - ran much better then the hesitation came back! Got myself a GFB Atomic boost controller thinking maybe the solenoid was gone burger, this has only allowed me to change the amount of boost im running and still have hesitation!!

Ok so figured maybe the car is demanding too much fuel so out went the standard fuel pump and in went a Walbro 255 LPH GS342, i didnt use the new sock as advised on the forums. Car ran better for the morning no issues what so ever took her for a good drive, couple of hours later and hesitation kicked in!

So ive since changed Bosch 02 Sensor, Walbro Fuel Pump, New AFM, New GFB Boost Controller....

Things to add I have no check engine light with or without green and black plugs connected, when starting car every now and then it may take a few seconds to start up ,the car will turn over but wont start straight away? Is this a timing issue which is affecting the car hitting full boost seen as shes a wrx after all running STi gear? The two would relate wouldnt they?

Any help would be awesome team as im lost on this one!? Yes i should have bought an STi but i love the classic and have plans in future for better mods as mentioned once funds are available.

[G-unit]

have u reset the ecu? that will clear codes i believe and hopefully be ok, sometimes the codes store in the ecu and need to be fixed ie o2 sensor then reset to clear the code

[brwnboy]

Hey, yeah i used the below from another site...Cant hurt to try again? I read elsewhere you should give your car plenty after allowing to warm following a reset of the ecu?

"ECU Reset

On early MYs (especially pre MY97) the ECU retards the ignition when knock is detected, however, it is very slow to advance the timing again. An ECU reset will restore the car to factory default settings. This will remove any stored fault codes and restore ignition advance. It is possible to reset the ECU by following these steps:

* Turn ignition OFF

* Connect Read Memory Connectors & Test Mode Connectors

(jumper 5) [black connectors] – (jumper 6) [green connectors]

* Turn ignition ON (engine off)

* Engine Check lamp turns on

* Depress accelerator pedal completely

* Then return it to the half-throttle position and hold it there for two seconds

* Release pedal completely

* Start engine

* Code is indicated by Pulsing lamp

* If a fault is detected - Check ECU Code

* If no fault is detected - drive the car sensible for a couple of minutes

i.e. until warm (do not run tall & do not thrash it!)

* When the ECU has been reset the Check Engine Light will flash

* Code is indicated by Pulsing lamp

* If a fault is detected Check ECU Code

* Turn ignition OFF & Disconnect Connectors

* If there is a fault Check Appropriate Sensor"

[Timmah]

Is it hesitating when cold or warmed up?

Have you tried unplugging the AFM, quick spin, then plugging back in, unplugging o2, then quick spin and see if the hesitation is going away??

I think i have the same blitz turbo timer, on idle it should be -48ish for there to be no vac leaks.

[kamineko]

just a thought, are the yellow injectors you installed known good? also what about the ecu? easy enough to swap that into the right car to check it

i had huge problems with a sti/loom conversion only to find half the parts i bought off trademe where stuffed to begin with

[Pappu1]

Does it hesitate at fill throttle or part throttle - is there a difference when doing either?

And once it's hesitating does it continue to hesitate all the way till redline or gets better once past a certain rpm?

[brwnboy]

 Timmah']

Is it hesitating when cold or warmed up?

Have you tried unplugging the AFM, quick spin, then plugging back in, unplugging o2, then quick spin and see if the hesitation is going away??

I think i have the same blitz turbo timer, on idle it should be -48ish for there to be no vac leaks.

Hey,

Just tried earlier tonight, allowed car to warm for 10mins turned off and unplugged 02 went for a drive up the hill came on boost and then....still playing up, ran it for a good 10mins. While up the hill i shut her off then plugged 02 back in, started her up and unplugged afm, car shut down. Started the car went for a drive back up the hill hesitation felt worse and didnt want to give her much pulled over after 2mins shut down, plugged in afm then went for a boost, still hesitating but felt better than afm unplugged. Idle is not steady when i first start the car idle goes up to around 1250 - 1500rpm, the gauge reads -31 is this normal when cold? the boost gauge moves between -47 and -49 when warm, would this indicate a leak?

[quote name='kamineko said:

just a thought, are the yellow injectors you installed known good? also what about the ecu? easy enough to swap that into the right car to check it

i had huge problems with a sti/loom conversion only to find half the parts i bought off trademe where stuffed to begin with

Hey,

The ECU i bought from a member on here so I would assume all good, it doesnt have a 6S sticker on top but has the details in vivid on the outer shell V3 Sti Ra 6S, connection board on the ecu reads D35 (url]http://www.clubsub.org.nz/forum/index.php/topic,9493.0.html[/url]) <--- Big Ups for the post ;D

Cant hurt to try and find one, if anyone has a spare 6S ECU that would be awesome to borrow for testing?

The injectors are from Trade Me, i had them checked, cleaned and seals replaced down at diesel n turbo in Welly, I was told they were all good.

[brwnboy]

 pappu said:

Does it hesitate at fill throttle or part throttle - is there a difference when doing either?

And once it's hesitating does it continue to hesitate all the way till redline or gets better once past a certain rpm?

Hey,

Both but seems to be mainly full throttle when putting load on the car, boost gets to around 0.84kg/cm2 then starts playing up, part throttle isnt as bad, but again till i get to 0.84kg/cm2 = 11.94psi it starts playing up again? I should be reaching 1.02kg/cm2 = 14.50psi atleast? Car continues to keep hesitating until i back off the pedal but continues to accelerate when on the gas.

[kamineko]

cool, few people bother to get the injectors checked

umm, sort of pissing in the wind here, bad knock sensor?

[Timmah]

 kamineko said:

cool, few people bother to get the injectors checked

umm, sort of pissing in the wind here, bad knock sensor?

Don't think that the Yellow Tips off the Legacy's could cause this too?? Seeing as they're different from the WRX ones?

[brwnboy]

 kamineko said:

cool, few people bother to get the injectors checked

umm, sort of pissing in the wind here, bad knock sensor?

Haha, well not so cause my car is sill playing up!

Ill give the knock sensor move a go in the morning and update once ive taken her for a run.

[G-unit]

wouldnt a knock sensor put it into limp mode tho? say 7-8psi but run ok?

anyway keep us informed

[brwnboy]

 Timmah']

[quote name='kamineko said:

cool, few people bother to get the injectors checked

umm, sort of pissing in the wind here, bad knock sensor?

/quote]

Don't think that the Yellow Tips off the Legacy's could cause this too?? Seeing as they're different from the WRX ones?

The injectors came in the rails....Diesel n Turbo told me they were genuine

02 sensor wiring from loom is black and 2x white, i matched the new 02 sensor up to those colours is this right? Would conecting the white wires incorrectly cause a problem? How can i test this prior to moving the knock sensor, think id do knock sensor relocation as a last resort really....

[kamineko]

no, the o2 white wires are just the heater, polarity is not important there. black is the sensor output. good earthing to your block is helpful

o2 is only used during cruise anyway

and yeah, excessive knock can trigger limp mode, but a cracked knock sensor typically gives all sorts of problems on an early legacy TT so its worth checking out

some more random things to check:

block off the BOV incase its leaking on boost - would have to be pretty stuffed tho

pull out and clean the cam/crank sensors

[brwnboy]

Hey guys, took car for a good drive today after swapping in a another coil pack, went well but still hesitating.

I can confirm that the car hesitates only under full throttle like changing down and putting the foot down or heavy accelerating, I can gain boost and car does not hesitate while gradually increasing throttle all the way to redline. Car idles between -49 and -51cm/hg and was hunting today after a good boosting.. Does this indicate an air leak?

Checked my pod filter and theres a small amount of wear n tear, the sponge is there but the metal netting has perished, about the size of a 50c coin... ???

[Timmah]

 brwnboy said:

Hey guys, took car for a good drive today after swapping in a another coil pack, went well but still hesitating.

I can confirm that the car hesitates only under full throttle like changing down and putting the foot down or heavy accelerating, I can gain boost and car does not hesitate while gradually increasing throttle all the way to redline. Car idles between -49 and -51cm/hg and was hunting today after a good boosting.. Does this indicate an air leak?

Checked my pod filter and theres a small amount of wear n tear, the sponge is there but the metal netting has perished, about the size of a 50c coin... ???

Cleant your IACV at all?? Hopefully fix the idle hunt.

But as a precaution, is your pod secured down so it can't vibrate at all? And blocked off from the engine in a cold air box type thing??

EDIT: Your idle is the same as mine so I doubt there's any leaks

[EJ20T]

Is the fuel pressure reg plugged in?, maybe a long process but you could try swapping back to your og ecu afm injectors, and then run 1 bar on it and see how the car reacts, if its ok then you have elminated everything else on the car. By the sounds of your problem its either the ignition breaking down, the mixture lean or over rich or the ecu is doing something stupid with the timing/fueling

[Guest]

im having the same sorta issues man.expect my cars drives fine.only hesitates when it packs a shitty

its rather anyoying i cant fin the issue aswell

so far what iv done and hasnt helpd

new plugs,all leads and coils are sweet

has a walbro fuel pump

brand new airflow meter from subaru-genuine

airbox back on with new genuine filter

fuel additive

universal o2 sensor

cleand idel controll valve and re placed gasket

tested another good working bov-no change

upper engine cleaner.

iv kinda given up and decied im just guna save and get it taken in some were,theres no coeds that are stored in my ecu and none coming up when i check them

so if you find what it is let me know

chur

[brwnboy]

 Timmah']

Hey guys, took car for a good drive today after swapping in a another coil pack, went well but still hesitating.

I can confirm that the car hesitates only under full throttle like changing down and putting the foot down or heavy accelerating, I can gain boost and car does not hesitate while gradually increasing throttle all the way to redline. Car idles between -49 and -51cm/hg and was hunting today after a good boosting.. Does this indicate an air leak?

Checked my pod filter and theres a small amount of wear n tear, the sponge is there but the metal netting has perished, about the size of a 50c coin... ???

Cleant your IACV at all?? Hopefully fix the idle hunt.

But as a precaution, is your pod secured down so it can't vibrate at all? And blocked off from the engine in a cold air box type thing??

EDIT: Your idle is the same as mine so I doubt there's any leaks

Yea ive cleaned the IACV, no harm in doing anutha can of upper engine cleaner through the subbie tho. POD is secured down now, im thinking there may be a leak around the air filter itself, ill grab a new o ring seal over the weekend.

Whats the deal with the injectors being STi or Legacy as asked above? Is there a difference as the ones i have are yellow tops and i guess i thought all yellows were 440cc? The car is back firing after a bit of gas and easing off throttle, this maybe due to not upping the boost whilst problem is around tho...

Going to go over the intake, cant see any visible leaks or cracks but will do another check during the week and report back...New hose clamps and maybe time to replace the intercooler piping as well...

[quote name='EJ20T said:

Is the fuel pressure reg plugged in?, maybe a long process but you could try swapping back to your og ecu afm injectors, and then run 1 bar on it and see how the car reacts, if its ok then you have elminated everything else on the car. By the sounds of your problem its either the ignition breaking down, the mixture lean or over rich or the ecu is doing something stupid with the timing/fueling

Yes FPR is plugged in. I changed the lines on this also...Car back fires which would indicate over fuelling?

[Pappu1]

Have u still got ur stock afm and ecu and inj to try on so as to eliminate everything else on the car?

Pm kingpin on here

He did the exact same thing to his Wrx and managed to get working perfect

He may know what bits needed tweaking with the mods u did

I know he had some issues but they were all sorted in Te end and car pulled good

[Guest]

prty sure it doesnt matter if theres a leak on the pod side of the afm.but itl matter on the other side,i did a few runs in my car without a pod just afm.didnt seem like it was a issue

[brwnboy]

 pappu']

Have u still got ur stock afm and ecu and inj to try on so as to eliminate everything else on the car?

Pm kingpin on here

He did the exact same thing to his Wrx and managed to get working perfect

He may know what bits needed tweaking with the mods u did

I know he had some issues but they were all sorted in Te end and car pulled good

Hey man, thanks for that I've PM'd King Pin......

I do have all the stock gear on hand , ill wait to hear from King Pin prior to trying all the old gear out and go from there, if i dont hear from him before Saturday ill go back to standard inj, ecu and afm to see if any probs...

[quote name='sti8u said:

prty sure it doesnt matter if theres a leak on the pod side of the afm.but itl matter on the other side,i did a few runs in my car without a pod just afm.didnt seem like it was a issue

Sweet as, thanks for the reply. Ill keep you posted also on any changes or improvements fingers crossed.

On another note would the temp sensor have any involvement with the probs im having? Starting probs (takes a few turns for the car to start) and foot flat is where im having the hesitation....

[Guest]

algood,what makes you think a temp sensor would cause a flat spot when you plant it?

[brwnboy]

 sti8u said:

algood,what makes you think a temp sensor would cause a flat spot when you plant it?

Havent read too much into it, but from scouring over other forums most people have replaced their temp sensor when having similair issues? Checking some sites at the mo for further info....

Do you know what this controls or looks after during idle, normal driving conditions and WOT? Or does it not have any involvement at all?

Trying not to go too off topic here

[EJ20T]

If it backfires it means its got a missfire, it would have to be way over rich to backfire, you would see plenty of black smoke under boost. so its likely lean or ignition break down, are the plugs gapped to .7 to .8? you could have a poor powersupply or earth to the coil giving it weak spark.