VX L67 with 69mm TB Cold start stalling

[immortality]

Yep, I thought yesterday with the vac leak it may have sorted it as the leak would be leaning it out.

Good news it's no longer stalling. It's not perfect by a long shot.

When I have the laptop connected it's in diagnostic mode so I can't turn the thermo fans off which would be altering the IAC steps. 45 Steps at running temp idle with thermo's on. TPS 0.57v

It's also throwing a lean o2 sensor fault, L bank so that's going to need investigation.

I've attached a screen dump of the start up and a log.

VX L67 Cold start.png

vx v6 69mm cold start problem.xdl

Using The1 VX_V6_SC_A5K_enhanced_v1.3 XDF

[immortality]

I think maybe I need to reduce the decay rate (for the IAC) as it comes down very fast and then has to come back up a little to recover the idle RPM as it drops below the desired rpm.

[jenko]

play with the mixture before mucking with the idle speed stepper motor , as you have noticed the lean mixture is probably more the issue,
the more constant the fuel mixture the less the motors idle will fluctuate and therefore the less the stepper motor has to work

[immortality]

Yeah, I'll definitely be looking into the lean error code. I've got a new IR gun on the way as it's an easy way to see if any one cylinder is running leaner than the others.

Although I do think the decay rate is to fast for the stepper motor at this point I can't see anything in the tune that will allow me to adjust it.

[VL400]

In the log screenshot at about 9 seconds is where closed loop idle speed takes over. Until that point the PCM uses base steps plus some offsets. It does not do anything but decay the steps at a rate determined by the IAC decay table.

When closed loop idle speed takes over the PCM then tries to get the idle RPM to match the target. But before that point the steps need to be enough to keep it running and preferably slightly above the target, with the smaller IAC ports its likely going to need tweaking.

[immortality]

In the log screenshot at about 9 seconds is where closed loop idle speed takes over. Until that point the PCM uses base steps plus some offsets. It does not do anything but decay the steps at a rate determined by the IAC decay table.

When closed loop idle speed takes over the PCM then tries to get the idle RPM to match the target. But before that point the steps need to be enough to keep it running and preferably slightly above the target, with the smaller IAC ports its likely going to need tweaking.

I thought so too. Unfortunately I don't see a IAC decay table in this tune/definition to adjust. I've tried looking in earlier ecotec tunes but see nothing there either to compare to.

[immortality]

OK, time to become a little more learned.....

How do I find/define this table?

I figured out how to create a table, and to start to define the parameters etc, however I need to learn how to find the actual table location in the bin.

edit: i've been using the graphical table finder and using other IAC tables as a rough starting point to look through the bin. In the table I used the equation that was used in the 12p definition as well as other bins/XDF's I've looked at.

edit2: going off my previous data log. Coolant temp was around the 18°C and it dropped approx 35 steps/sec.

[VX L67 Getrag]

When I edit xdf's I find a similar code base with a more defined xdf & identify matching hex characters & add table from other xdf & if it looks good it should be pretty close!

It normally needs a lot of refining, but gets you in the ball park!

[immortality]

Yeah, I've been searching other XDF's but it seems it's not been defined on other ecotec/L67 definitions either. I think the VS ecotec XDF is about the most well defined file about?

I have found something that looks fairly close but I have no way to test it other than on a live vehicle.

I've attached my XDF if anybody wants to take a look/check.

edit:nope that's another table

[Holden202T]

yeah I can't seem to find much to do with iac decay