Problem with version 7 STi boost control

[chappell943]

Had the car plugged into my laptop and there was no stored knock learning and all the fuel trims were in order indicating a leak is unlikely.

[ben-jamminn]

 chappell943 said:

Had the car plugged into my laptop and there was no stored knock learning and all the fuel trims were in order indicating a leak is unlikely.

Blair, does this totally rule out knock sensor playing up? as suggested by titian?

You said everything seemed to be in order as far as what your laptop showed you, so I guess it must be something that isn\'t controlled by or seen by the ECU ???

Looks like I\'ll recheck the plugs.. :-\

[chappell943]

I can\'t be 100% but a hesitation could be caused by a large amount of timing being removed due to a faulty knock sensor, but when I plugged in there was no stored knock at all. Looking online earlier the maf sensor seemed like a common thing that fixed the problem when replaced, so maybe try another one to eliminate something else.

[ben-jamminn]

Yeah that\'s worth a shot, They\'re bloody expensive from memory :-\

[chappell943]

If you check the plugs, clean the maf again and reset the ecu and see if that makes a difference. If that doesn\'t help I\'m pretty sure I can log misfires through my laptop so we could try that although I\'m unsure what the story is regarding the check engine light and missfires.

[JWDRPN]

Iv got the same issue with my v7 hesitation i tried new afm new coils new plugs even after a full engine rebuild it still is doin it its driving me nuts

[ben-jamminn]

 chappell943 said:

If you check the plugs, clean the maf again and reset the ecu and see if that makes a difference. If that doesn\'t help I\'m pretty sure I can log misfires through my laptop so we could try that although I\'m unsure what the story is regarding the check engine light and missfires.

Yeah I gave the MAF a real good clean this avo, will check the plugs tomorrow after work. Can you confirm that battery disconnect resets ECU? or is it better to do it through your computer? Maybe when we both are free next I\'ll let you take the car for a spin and you\'ll get a first hand experience, as you can compare it to your v7

[chappell943]

Battery off and pump brake pedal a few times will do it, yeah I wouldn\'t mind experiencing the problem, we can always chuck my maf sensor in to see if that fixes it to. So does it only happy if you try accelerate under partial throttle?

[ben-jamminn]

Sweet!

Yep, and kicks in at around 4000 RPM, so I only notice it at \'slightly\' spirited driving, like I said merging with open road traffic, coming out of roundabouts, etc. I usually shift around 3000 RPM under normal conditions so I don\'t notice it 90% of the time. I work out near the airport so I notice it coming out of all the roundabouts down Johns road haha

[chappell943]

So am I right in saying it happens when coming onto boost? Eg if you go into 4th and put your foot flat from 2000rpm will it still happen at 4000 or will it come in earlier?

[ben-jamminn]

Doesn\'t seem to occur under flat foot conditions, I need to take more notice of all the exact conditions, but I only notice it at normal throttle position, just when accelerating through to 4000 RPM. Best to see for yourself I reckon!

[chappell943]

Yeah sounds like a bit of a tricky one, hopefully its an easy fix. Give me a text once you\'ve had a look at plugs and reset ecu and we can try get your car running good again!

[JWDRPN]

mines like that flat foot in 4th as boost creeps on the car feels like its being held back then boost will come on then repeat. (by this point iv back off not willing to blow it)

[ben-jamminn]

 JWDRPN said:

mines like that flat foot in 4th as boost creeps on the car feels like its being held back then boost will come on then repeat. (by this point iv back off not willing to blow it)

Sounds similar to me except mine doesn\'t occur at foot flat.

Bypass your boost control solenoid with a manual controller (boost tap, etc)

That\'s the first step in tracing the fault, if your boost fluctuation goes away its likely your solenoid is poked.

It fixed my boost fluctuation, it\'s just that I still have slight hesitation

[Pappu1]

 JWDRPN said:

mines like that flat foot in 4th as boost creeps on the car feels like its being held back then boost will come on then repeat. (by this point iv back off not willing to blow it)

have u had this diagnosed?

[JWDRPN]

no error codes no leaks all new spark plugs at the right gap new o2 sensors new maf sensor rebuilt heads... i put in a replacment boost controller..

i was told it was lightly to go after heads were rebuilt but its still there..

[boon]

Can\'t remember if you\'ve checked/replaced it but maybe one of the exhaust O2 sensors? If it doesn\'t happen flat-foot then I\'d suspect that, as flat-foot doesn\'t use closed-loop.

[Pappu1]

 JWDRPN said:

no error codes no leaks all new spark plugs at the right gap new o2 sensors new maf sensor rebuilt heads... i put in a replacment boost controller..

i was told it was lightly to go after heads were rebuilt but its still there..

does it boost well after flat spot?

what PSI?

did they do afr reading?

is it leaning out or det something and the ecu really pulled things back in some zones?

leaky bov?

[Marky]

Might be worth your trouble seeing about chucking it on a dyno (no shortage of options in chch) just to see if there\'s anything a bit more apparent in a controlled environment

Depends how much it annoys you I guess

[titian]

Ho Hum!! ???

A Knock sensor fault WILL NOT necessarily throw a code fault.

They cost $112 retail less on trade discount from winger. :-*

Bet it is this crucial sensor....Have seen this scenario before. Have also just changed one recently for a customer that had done/cleaned or replaced almost every other sensor,plugs re gapped etc...And still it had this maddening flat spot and occasional miss....NO code logged or discrepancies in the mapping. :\'( :\'(

Even Winger could not sort it out! ??? ???

After spending hours and many dollars (close to a grand!) I was asked about it.

Fault cleared as soon as knock sensor was replaced....Took me 20 min to sort it out!

Customer was so pleased that he insisted i took the $250 that he offered me! ;D

KNOCK SENSOR!!

[chappell943]

 titian said:

Ho Hum!! ???

A Knock sensor fault WILL NOT necessarily throw a code fault.

They cost $112 retail less on trade discount from winger. :-*

Bet it is this crucial sensor....Have seen this scenario before. Have also just changed one recently for a customer that had done/cleaned or replaced almost every other sensor,plugs re gapped etc...And still it had this maddening flat spot and occasional miss....NO code logged or discrepancies in the mapping. :\'( :\'(

Even Winger could not sort it out! ??? ???

After spending hours and many dollars (close to a grand!) I was asked about it.

Fault cleared as soon as knock sensor was replaced....Took me 20 min to sort it out!

Customer was so pleased that he insisted i took the $250 that he offered me! ;D

KNOCK SENSOR!!

Are you saying the knock sensor is pulling timing because it is detecting knocking that is not actually there resulting in a hesitation from the altered timing?

[titian]

 chappell943']

[quote name='titian said:

Ho Hum!! ???

A Knock sensor fault WILL NOT necessarily throw a code fault.

They cost $112 retail less on trade discount from winger. :-*

Bet it is this crucial sensor....Have seen this scenario before. Have also just changed one recently for a customer that had done/cleaned or replaced almost every other sensor,plugs re gapped etc...And still it had this maddening flat spot and occasional miss....NO code logged or discrepancies in the mapping. :\'( :\'(

Even Winger could not sort it out! ??? ???

After spending hours and many dollars (close to a grand!) I was asked about it.

Fault cleared as soon as knock sensor was replaced....Took me 20 min to sort it out!

Customer was so pleased that he insisted i took the $250 that he offered me! ;D

KNOCK SENSOR!!

/quote]

Are you saying the knock sensor is pulling timing because it is detecting knocking that is not actually there resulting in a hesitation from the altered timing?

The knock sensor is a high frequency microphone,for want of a better description. listening for detonation

If it is damaged in any way it still hears the "knock" But because the sound is not "true" the timing is altered to suit.

As far as the ECU is concerned a signal was "heard" so no code is acknowledged.

If there is a missing signal ECU will emit code. But not if the sensor is not "hearing" correctly

Clarified? ??

For the cost...Less than a tank of gas...Replace it. In fact replace it at least every 180,000km as it will be hard of hearing at this point in its life.

You will be surprised at the result!.......Damn i hate repeating stuff >

http://www.clubsub.org.nz/forum/index.php/topic,33060.0.html

[titian]

 JWDRPN said:

Iv got the same issue with my v7 hesitation i tried new afm new coils new plugs even after a full engine rebuild it still is doin it its driving me nuts

KNOCK SENSOR FAULT. ;D..Replace it...Simple ;)

[ben-jamminn]

 titian']

[quote name='JWDRPN said:

Iv got the same issue with my v7 hesitation i tried new afm new coils new plugs even after a full engine rebuild it still is doin it its driving me nuts

/quote]

KNOCK SENSOR FAULT. ;D..Replace it...Simple ;)

Priced a knock sensor today from Armstrong, $120.

Will be replacing it this weekend

[Stoffa]

I used to be an urgent courier and we used to deliver a crazy amount of knock sensors on 1 hour deliveries, so very common to be replaced