Vt-vx rev hang RESOLVED!

[StingRedVX]

Recently purchased a factory manual VX S pac. Unfortunately once again I have come across the dreaded ‘rev hang’ between gears.

I’ve read through every thread in here and no one seems to have a confirmed ‘fix’. A lot of people dismiss the problem altogether blaming it on the dual mass flywheel. Yes, it does sound logical. However it is incorrect. My last commodore was a factory manual vy with a confirmed dual mass flywheel and it did not have this problem at all.

This leads me to believe there is a mechanical fault or it’s exclusive to how the VT-VXs were tuned regarding IAC.

Just to clarify, it’s reving freely and dropping quickly in neutral and drops fast when changing down gears.

I’ve gone to inspect the IAC and realised my throttle body and plenum is in dire need of a good clean out. I also have access to very cheap parts through work so I’ll be cleaning it all out and replacing my TPS and IAC.

Has ANYONE been able to confirm a fix for this or is anyone on here an ex Holden tech that has any proper information on this issue?
Hoping I don’t need to create a custom tune!

I will not stop until I figure this out!
I won’t settle for leaving it disconnected! Haha

 

[krusing]

Don't load the parts cannon yet !

Get is scanned to see what DTC's it may have,
not all DTC's activate the MIL,
Then take it from there.

 

[Lex]

Recently purchased a factory manual VX S pac. Unfortunately once again I have come across the dreaded ‘rev hang’ between gears.

I’ve read through every thread in here and no one seems to have a confirmed ‘fix’. A lot of people dismiss the problem altogether blaming it on the dual mass flywheel. Yes, it does sound logical. However it is incorrect. My last commodore was a factory manual vy with a confirmed dual mass flywheel and it did not have this problem at all.

This leads me to believe there is a mechanical fault or it’s exclusive to how the VT-VXs were tuned regarding IAC.

Just to clarify, it’s reving freely and dropping quickly in neutral and drops fast when changing down gears.

I’ve gone to inspect the IAC and realised my throttle body and plenum is in dire need of a good clean out. I also have access to very cheap parts through work so I’ll be cleaning it all out and replacing my TPS and IAC.

Has ANYONE been able to confirm a fix for this or is anyone on here an ex Holden tech that has any proper information on this issue?
Hoping I don’t need to create a custom tune!

I will not stop until I figure this out!
I won’t settle for leaving it disconnected! Haha

Clean the throttle body & plenum & iac first. See how you go from there.

Have you confirmed its factory manual?

 

[StingRedVX]

Clean the throttle body & plenum & iac first. See how you go from there.

Have you confirmed its factory manual?

Yes, confirmed factory manual. M35 stamped on compliance plate. I also need to do the valley gaskets on the weekend so I will clean everything else up during that. Don’t have access to any scan tools so unable to scan for codes. Could possibly try bridging pins 5 and 6 for flash codes

 

[Ginger Beer]

Yes, confirmed factory manual. M35 stamped on compliance plate. I also need to do the valley gaskets on the weekend so I will clean everything else up during that. Don’t have access to any scan tools so unable to scan for codes. Could possibly try bridging pins 5 and 6 for flash codes

Supercheap auto use to scan codes for free, may be an option

Shot gun approach to fault finding/fixing can end up expensive, and still not fix the issue

 

[StingRedVX]

Did some investigation today. My theory is that the IAC isn’t closing fast enough when letting off the throttle.
It makes sense because when down shifting, your foot is already off the throttle and the IAC is already in the position (meaning no rev hang) Whereas coming off the throttle it has to readjust and isn’t doing it fast enough. Hence why the revs jump a tiny bit then slowly come down.

 

[StingRedVX]

So I ended up doing valley gaskets over the weekend and decided to clean everything else up whilst I was at it. IAC was covered in thick black soot/oil/sludge and so was throttle body. Cleaned everything up replaced IAC and TPS.

Still rev hangs!
Grrrrr
Looks like it’s a tuning issue as I’ve proven it’s not the flywheel, I’ve proven it’s not the throttle body or sensors and I’ve proven it’s not the throttle cable.

Anyone know how to tune out the IAC during gear changes? Or maybe I can run it on a switch…

 

[VF2R]

I hear you ... saying it isn't related to the dual mass flywheel.

Makes total sense.

Funny thing is my VF ute had the same hang..annoyed hell out of me. When I went to a solid flywheel it stopped doing it..coincidence?

My V8 manual did the same...then I went to a solid flywheel and again...rev hang disappeared.

Just my own personal experience btw.

 

[StingRedVX]

See the thing is, my last vy was dual mass and it didn’t do this at all. It’s like Holden retuned the “anti-stall” on the VYs.
I will carry out some further tests to prove this is a IAC tuning issue

 

[VF2R]

See the thing is, my last vy was dual mass and it didn’t do this at all. It’s like Holden retuned the “anti-stall” on the VYs.
I will carry out some further tests to prove this is a IAC tuning issue

Ok. Like I say it may just be a 'coincidence'. Let us know how you get on.