VX L67 with 69mm TB Cold start stalling

[immortality]

Just downloaded that HxD hex editor but it's in bloody spanish. Anybody know how/where to change the language option?

edit:found an english version.

[Holden202T]

lol!

[immortality]

Just thought I would update this,

I haven't really worried about this as it was no longer stalling, however since fitting the CAI the issue seems to have improved somewhat. Since I had bought a new toy from VL400 I thought it was only fair to test it out on the VX and get a log of a cold start this morning.

I've attached a copy of the monitors from this morning as well as the original one. Now it seems that stepper motor does a double take and adds a few steps during the initial decay. Idle isn't dropping as much so that is a win. I haven't changed anything in the tune since the original changes so not sure what the story is but I'll take it I guess.

One day I would like to figure out how it calculates the IAC decay rate though.

The only other difference is it was a few degrees cooler this morning.

[immortality]

Thought I would update this thread.

I have altered these tables IDLE Air Fuel Time Out - P/N V's startup Coolant Temp and IDLE Air Fuel Time Out - Drive V's startup Coolant Temp using the tables from the VS SC bin. This has reduced the IAC decay rate, Idle doesn't drop as fast and it's not dropping below the required idle like it did before which has allowed me to reduce the IAC - Motor Park Position During Crank V's CTS a bit so the engine doesn't rev quiet as much when it first fires. Might save just a little fuel

I'll add a screen shot at a later stage to show the differences.

[immortality]

Thought I would revive this thread as the issue is related.

Been getting a weird intermittent belt squeak type noise for a while and it's gotten worse of late, happens more predominately when the engine is warm but only seems to do it just as the engine is returning to idle, never at idle and worse on a cold morning or evening. Never managed to replicate it sitting in the driveway idling etc.

Anyway the missus was getting annoyed with it so time to pull finger, went out and got some new serpentine belts, put em on and thought that would be the end of it.... well no

Anyway after chasing my tail for a bit I have worked out the noise is actually occurring in the IAC passages. Recently I had had an issue where the throttle was sticking just a touch, rather than cleaning it I had just opened the butterfly a touch (as I was in a hurry to get somewhere) which sorted out the sticking throttle thinking back is also when this issue got worse. Anyway, pulled the TB off, gave it a good clean and thought that would be the end of it.......think again

Pulled it apart again today and I have just rounded off the edge where the IAC passage bore goes through to behind the TB blade, right where the IAC stepper motor pintle travels past it, my theory been the air is whistling over this edge.

Now to see what it does, here's hoping.

Since changing some of the setting over to the earlier VS SC tune it seemed to be using more fuel so I have put those settings back to standard and started to look else where to sort this issue. What I have figured out is that the double step (in IAC steps) in the last screen shot is when the AC compressor engages. It also looks like the various settings labelled under the headings Fuel air Timeout - are related to the IAC decay rate. Hopefully I'm on the right track now.

edit : still doing it but not quiet as bad. Maybe I try a different IAC stepper motor? Not ever had anything like this before.

[HQ355]

Have iac steps changed ? Bushes in throttle shaft not worn ? I'd say your heading in right direction

[immortality]

Yeah, they would have as I have closed up the TB blade a touch to make the IAC open a bit more. TB has needle roller bearings for the butterfly shaft

[HQ355]

When did roller bearings go in ? I'd say there's more air gap in them than a bush ? Regardless of noise it's pointing to vac leak, and higher fuel use is another givaway

[immortality]

Holden started fitting needle bearings to TB's somewhere around the VR models I believe.

I cleaned it out with TB cleaner, I was tossing up whether to strip it right down and re-grease the bearings, would assist with sealing em too.

Edit. I've cleaned out plenty of these types of TB's in the past, never seen this issue before with this noise. I think another IAC motor is the next step, maybe the pintle is loose or moving inside the passage causing the noise?

[The1]

does it only stumble on first cold start? or is this issue every start? As fuel pumps on those models seem to have the valve issue, where it leaks all the fuel out of the rail overnight back to the tank, so first start takes a bit to get the fuel pressure back up, you can check this by turning the key to on a few times to get the pump priming a few times and get the pressure built backup.