club.liberty.asn.au

Experiencing a noticeable rattling/vibration under heavy acceleration generally when shifting from 1st to 2nd (Auto) from my exhaust. Happens most commonly in S# mode and S mode if I plant it. The source seems to be coming from below the center console but of course this is just a guess. This is obviously annoying but wait it gets better ...

Was told this noise/rattle/vibration is being picked up by the knock sensor which is the main cause of the engine cutting out for a sec and then springing back to life when under heavy acceleration. Not a great feeling obviously while trying to pull away at the lights.

Had the guys at Daadler Exhaust take a look at it and his professional opinion is he wouldn't touch it with a 10 ft pole. Too many variables and 3 points where it could be occurring. The problem he said was by adjusting something up the front, it can and most likely will, wreck havoc at the end section. He also said I could spend $200 and he might not have made any progress. His final suggestion was to return it because it obviously isn't the right fit for my lib. Oh, and the best bit, they'll probably just say it wasn't fitted properly by my mechanic. Great, just great.

So, does anyone else have a AVO TBE and experienced a similar issue? If so how did you go about fixing it? Is the rattling exhaust the real reason for the engine cutting out? Should I bother with the whole process of returning it?

Any suggestions about any other options would also be much appreciated.

Nothing more frustrating owning a car which doesn't like it when you stomp the accelerator.

I hope the rattle is not pinging

I'm in Collingwood if you'd like to spend an hour or two diagnosing and logging
Is the car tuned?
Who installed the dump etc...
Complete list of mods?
Regularly maintained by who?

Thanks for the offer Ben!

I may just take you up on it seeing as Dashcommand is a POS when it comes to diagnosing issues like these.

Car is KIDo tuned and exhaust installed by a known mechanic on this forum who also maintains my car.

All mods listed in my sig. Let me know if you're having trouble seeing them.

The exhaust noise is interesting, and it may be an idea to have avo take a look if you bought it new.

In regards to engine momentarily shutting off due to knock - who told you this? This is utter rubbish. What you're describing is either boost cut (due to a boost spike) or a fuel cut (if you're over revving into the 7000rpm+ range). Boost spikes are a bad thing, and most likely will be due to something wrong with the tune and you can easily pick this up through logging (your logged boost will be higher than what the tune asks for. eg. if you're tuned for peak of 17psi, and you see 19 or 21psi reading in your log). Fuel cut is also quite simple to diagnose, you can read it in the tune tables or ask your tuner to tell you what rpm fuel cut is set at.

Both are a safety measure by the ECU, it will cut boost if it overboosts (spikes) and it will cut fuel if you over rev.

Can your exhaust tic off the knock sensor? Very very unlikely (they're not near each other), but stranger things have happened. Can too much knock sensor signal shut your engine off momentarily? Hell no. That's not only not how the knock control works, but it also wouldn't make any sense as a knock control strategy.

Post up how you and Benny go. If it's just the exhaust making noise, it shouldn't be a biggie in terms of performance. I'd check clearances between the pipes and car, loose bolts, cracked heat shields etc.

AVO exhaust sold through tuspeed so not entirely sure what my options are. Tbh I'm happy with the exhaust and the note so would like to try every other option before this one.

Thanks for the info Alexi , maybe something Benny will be able to confirm for me. Pretty certain it isn't fuel cut as it generally happens at the beginning of the rpm range in 2nd gear when under acceleration.

Was told the knock sensor was picking up the noise and confusing it for a bad batch of fuel which is why it is cutting out. If this isn't the case then it should be an easy fix? Just trying to verify the exact cause so I know what direction to take.

Was thinking of purchasing some heat shield exhaust wrap as I located a protruding 'lump' on the middle heat shield (bolt behind the heat shield) today which seems to be the most obvious culprit. Probably at most a 4mm clearance between it and the exhaust and it seems to be in the area that the noise comes from. At least it should stop the noise/vibration but what you're saying is it may not solve the cut out problem. Which is obviously the most critical...

Logging might be the best bet for now just to get to the bottom of it.

Here's a quick summary of the fix:
Used btSsm to diagnose avcs vvt out of sync.
Tried one new ocv swapped into each side and logged to isolate the issue to just faulty ocv's and not ocv oil supply issues (eg banjo bolt filters etc)
One new ocv did not fix the sync issue so another was installed to completely fix avcs out of sync issue.
Whilst we did that we noticed:
a missing turbo heatshield bolt, we bent the shield away from the bracket for extra rattle free clearance.
a loose up pipe bolt: tightened

Then the car got tuned again by Matt with a bpt 3 port also installed by Matt.

The car still had clanking issues on throttle lift.
We put the car on stands and inspected the 3" tbe install.
We found:
Slight rubbing contact of the down pipe on the iirc gearbox x member (4mm clearance)
We twanged the heatshield between the prop shaft and mid pipe and noticed it was rattling on the prop shaft center bearing and resonating itself as well.
So we cleaned and clearanced it, added extra bends along the length of it, and lastly added a little Resomat to the edges to quell any remaining resonance.

A biscuit of wadded aluminium foil about 5mm thick was wedged between the DP and the x member, at least until the member can be bent or dremeled (preferably bent) clear of the DP.

End result: one happy owner with one very smooth postFL GT...

bigBADbenny wrote:Here's a quick summary of the fix:
Used btSsm to diagnose avcs vvt out of sync.
Tried one new ocv swapped into each side and logged to isolate the issue to just faulty ocv's and not ocv oil supply issues (eg banjo bolt filters etc)
One new ocv did not fix the sync issue so another was installed to completely fix avcs out of sync issue.
Whilst we did that we noticed:
a missing turbo heatshield bolt, we bent the shield away from the bracket for extra rattle free clearance.
a loose up pipe bolt: tightened

Then the car got tuned again by Matt with a bpt 3 port also installed by Matt.

The car still had clanking issues on throttle lift.
We put the car on stands and inspected the 3" tbe install.
We found:
Slight rubbing contact of the down pipe on the iirc gearbox x member (4mm clearance)
We twanged the heatshield between the prop shaft and mid pipe and noticed it was rattling on the prop shaft center bearing and resonating itself as well.
So we cleaned and clearanced it, added extra bends along the length of it, and lastly added a little Resomat to the edges to quell any remaining resonance.

A biscuit of wadded aluminium foil about 5mm thick was wedged between the DP and the x member, at least until the member can be bent or dremeled (preferably bent) clear of the DP.

End result: one happy owner with one very smooth postFL GT...

Sounds like a task!
Did you check Engine Mounts & Pitch ?

bigBADbenny wrote:Here's a quick summary of the fix:
Used btSsm to diagnose avcs vvt out of sync.
Tried one new ocv swapped into each side and logged to isolate the issue to just faulty ocv's and not ocv oil supply issues (eg banjo bolt filters etc)
One new ocv did not fix the sync issue so another was installed to completely fix avcs out of sync issue.
Whilst we did that we noticed:
a missing turbo heatshield bolt, we bent the shield away from the bracket for extra rattle free clearance.
a loose up pipe bolt: tightened

Then the car got tuned again by Matt with a bpt 3 port also installed by Matt.

The car still had clanking issues on throttle lift.
We put the car on stands and inspected the 3" tbe install.
We found:
Slight rubbing contact of the down pipe on the iirc gearbox x member (4mm clearance)
We twanged the heatshield between the prop shaft and mid pipe and noticed it was rattling on the prop shaft center bearing and resonating itself as well.
So we cleaned and clearanced it, added extra bends along the length of it, and lastly added a little Resomat to the edges to quell any remaining resonance.

A biscuit of wadded aluminium foil about 5mm thick was wedged between the DP and the x member, at least until the member can be bent or dremeled (preferably bent) clear of the DP.

End result: one happy owner with one very smooth postFL GT...

One very happy owner

Thanks again Benny. Really appreciate your time and effort on this especially when dealing with such a n00b. I can now add heat shield to the list of instruments that I can play/twang.

That drive home has never been so enjoyable

Stay tuned for info regarding AVOs possible revisions to the dump or mid and in the meantime consider a roll of dei ti wrap to shield the dump heat from the auto box...

Not much of a task, between myself and Jayson, maybe 3 sessions of a couple of hours each, plus a tune revision from Matt, just methodically going through the issues until each was eliminated.

It's a combination of research, knowledge, experience and logic.
Jayson is up to speed and with that confidence could repeat the process solo if required.
But it's more fun to team up