07 Gt SPEC-B engine jerking in low revs half/full throttle

[cal_egan]

hey guys. I have had some work done by all star garage in perth. Just a tune. they got her up to 185kw which was impressive. i have a new factory head gasket, driveshaft, sparkies, basically a brand new engine after i was having some over heating issues.

for the past couple of months between 2500 and 4000 rpm the car jerks back and forth in any gear. it sort of feels like lag but more violent and it never used to do this. im thinking it could be a back pressure issue as i do hear some air escaping the hoses which the guys at all star is because i have some leaks. i was just wondering if anyone may be able to diagnose the issue for me?

cheers.

callum.

[shav]

mine does this too a bit when under load. Feels like a sticky throttle or something. Be interesting to find out what it is too.

[sharpie]

very common on my07/08. kinked boost hose going to wastegate actuator due to manifold/turbo design. i used to replace the small wastegate hose with some longer vaccum hose and looped it so air will not get restricted.

note: this thread needs to be moved.

sharpie.

[bosc0]

very common on my07/08. kinked boost hose going to wastegate actuator due to manifold/turbo design. i used to replace the small wastegate hose with some longer vaccum hose and looped it so air will not get restricted.

Interesting... something to look at.
I was under the impression this was a common issue due to the drive by wire system, which can be tuned out.

[KiDo_Tuning]

very common on my07/08. kinked boost hose going to wastegate actuator due to manifold/turbo design. i used to replace the small wastegate hose with some longer vaccum hose and looped it so air will not get restricted.

Interesting... something to look at.
I was under the impression this was a common issue due to the drive by wire system, which can be tuned out.

Depends on the cause, can also be the rough Target boost table delivery 'pumping' the wastegate as there is plenty of tunes that just lift target boost at the right of the table not looking at the overall shape

[bosc0]

Just reading the original post and whats described isn't what i'm referring to. My issue is at much lower rpm and in stop start traffic. A combination of anti-stall and DBW i've read, which can be tuned out apparently.

A similar issue above 2500 and to 4000rpm would be as mentioned boost related, or maybe even spark breakdown?

[GTB Liberty]

Just reading the original post and whats described isn't what i'm referring to. My issue is at much lower rpm and in stop start traffic. A combination of anti-stall and DBW i've read, which can be tuned out apparently.

A similar issue above 2500 and to 4000rpm would be as mentioned boost related, or maybe even spark breakdown?

Turn off the airconditioning ... See. If it still occurs?

[bosc0]

A/C....do not use in winter and i don't appreciated the fact that you western Australians continue to rub that in our face

[Robbks]

A/C....do not use in winter and i don't appreciated the fact that you western Australians continue to rub that in our face

I use mine in winter more...
fastest way to unfog the widowzz

as a trained AC tech,
can people please leave the AC on all the time. it keeps teh lubrication oil well dispersed in the system preventing the seals from drying out/ cracking and you losing your gas and needing a re-charge and new seals.
modern systems use very little engine power and are efficient.
AND when you ask for >70% (maybe higher) throttle, the AC system disengages anyway as it also does with high rpm
so when you need the power, the AC is not taking any.

[bosc0]

as a trained AC tech,
can people please leave the AC on all the time. it keeps teh lubrication oil well dispersed in the system preventing the seals from drying out/ cracking and you losing your gas and needing a re-charge and new seals.
modern systems use very little engine power and are efficient.
AND when you ask for >70% (maybe higher) throttle, the AC system disengages anyway as it also does with high rpm
so when you need the power, the AC is not taking any.

Do use for 5 mins every morning for this reason

[bigBADbenny]

^^^ Great advice!

[Robbks]

Do use for 5 mins every morning for this reason

Nice..!!
i'd just leave it on
keeps the evaporator cleaner and none of that horrible musty smell in the car

[bosc0]

A/C is always on when Climate is, but climate is often off as it's a real annoying system. Sunroof for fresh air.
A well looked after A/C system should never need regassing. If it does, its due to a leak correct?

[Robbks]

A/C is always on when Climate is, but climate is often off as it's a real annoying system. Sunroof for fresh air.
A well looked after A/C system should never need regassing. If it does, its due to a leak correct?

not really.

the seals do leak over time, especially with expansion and contraction due to heat/ cold/ movement, no matter how well cared for they are.
that lets in air, and within that air is moisture.
the water/ moisture is incompressible and can result in high system pressures.
AC oil is hygroscopic and it does a good job at locking and retaining the moisture in the receiver drier (full of dessicant) but once it's saturated you'll get corrosion in the pump and pressure issues.

for $100 every 5 years (dealers recommend sooner of course) for a quick vac out, re-gas and oil top-up, it's good insurance.

[sharpie]

poss a tune issue its just what ive seen at Sti. Most my07/08/09 have a kinked hose to the actuator causing a boost surge. Anyway get a tune......stuff driving around with crappy dbw and boost tables!