Idle & Off Throttle Hang - Sometimes

[Monarols71]

More weirdness.
Started car from cold, cam sensor signal intermittently AWOL as before, and even when up to temperature.
Turn ignition off, restart car, cam sensor signal doesn't miss a beat.

[Monarols71]

"Item Lists > Engine Data Only > Cam Signal"

[brindo]

Please excuse the dumb questions, but apart from any problems that the DTC 49 may cause, is there a Throttle Follower function in the Series 3 PCM to adjust the rate at which the IAC valve returns or starts to return? Or is there a Throttle Cracker function in the PCM that can be changed to prevent the IAC opening up more after a certain speed? Or do these only need adjusting if using a non standard throttle body?

I have a similar issue with rpm hanging up in my Series 3 VS, but being a manual, it is not as much an issue as it is with an Auto. I also use an LS1 throttle body.

Thanks

[Holden202T]

i haven't played with these settings on the VS but i just recently had some issues with a VR V8 auto, due to the cam and the higher idle, it would actually keep the car at 60kms with zero tps on a flat road, so i reduced the "iac - throttle crack offset vs rpm" ... i left it as it was at idle settings just turned it down a bit at rpms above idle .... it didn't fix the problem completed but it did help alot, also could have decreased them more if i had the car for longer i guess ....

so the question is, is the same or similar tables in the newer code!

[Monarols71]

These are the only ones I can find.
Are they too high considering our idle steps are now around the 20 mark?
These tables haven't been changed since I changed the throttle screw to get the steps down as advised, but I did ask in the very first post.
Regards

[Holden202T]

the crank table i would say will only do anything when you are starting the engine ..... the other one.... im not sure what nornal load you would be seeing when your having the issues .... i guess you could always try and decrease the table and see what it does.

[Monarols71]

Thanks. I guessed it wasn't any problem because nobody said we had to drop the IAC settings. But we know the problem we have to fix before looking at any tables etc. Good old DTC49.
I suppose we'll have to beg, borrow, buy or steal another distributor or OEM hall sensor plate (can't buy that), even if it's purely to test whether or not that is the fault.
Intermittent faults are always such fun, aren't they.
Thank you all for your assistance and ideas.

[brindo]

I haven't done any logs of the idle hang in my car, but it only occurs when the engine is cold. I don't know the exact temp when it stops happening, but suspect it is somewhere around a coolant temp of 70 deg C which is where I have set the BLM to be active. But when it is cold, the gear changes are much smoother, and when it is hot, there is some hesitation evident during gear changes.

Is this a similar situation to what you are seeing in your car Monarals71?

Thanks

[Holden202T]

that sounds to me like the revs are dropping more when you off the throttle and hense you need to push the throttle down more to get the revs back up when applying the clutch on the next gear, but when its colder it keeps the revs up more and hense throttle open more so less required from your foot....

if this is the case you might be able to change it when cold via the cold higher idle IAC settings ....

[Monarols71]

Hi brindo. Ours does it hot or cold, but seems to do it more when hot. But then, I suppose that is what the temperature is more.
But I have to cure our DTC49 before I start chasing the tune, as I agree with THE1, that because the engine is not running sequentially, it's fuelling more than it should which is most likely causing the hang.
But going by the last logs I did, I think the coil might be sus. I don't understand the electrics of it, but (going on past experiences) temperature can make them play up. In our case it Throws DTC49 when cold, restart car when warm, no DTC49.
Oh well, more testing on the weekend.
Regards