idle specific issue

[A80Avant]

Hello all,

im struggling a bit with the following problem:
Although idle seems to work nicely on most occasions, even on high electical load it does not dip that much, i have this problem:

as im cruising, if i step on the clutch and go to neutral while the car is still moving, and on top of that if i press on the brake slightly, the rpm needle as it drops towards 1000rpm, it dips, as if it will stall, then jumps up and settles to my idle speed.

i have tried various idle configurations to avoid this from happening, all unsuccesfull

I presume that this happens because as the car goes to idle config once the gear is out and TPS=0, there is not enough air allowed through the idle valve to allow for the idle settle properly without dipping.

I tried using min PW allowed up to 30-35% and above that it makes my idle really high so i dont like it.
This somehow helped a bit, but not much.

I tried playing around with PID and deadbands, again without any real change.

I tried altering the PW in hardware settings, again without real luck.

can you help me with this one? which area of the idle settings should i focus on?


what does the IAC delay do as well?

thanks
vasilis

[A80Avant]

tried a few more setups today and realised that if i keep D to zero or a very low value, it seems to be able to hold the idle put, without issues for that specific condition.

idle overall seems a bit high, so i may need to adjust the TPS once im happy with this setup.

ill report back

[UrS4boy]

I think you needed to mention that this is a VEMS-equipped car, not Motronic. If it was Motronic, I would be telling you that your Idle Stabilization Valve (ISV) is dirty and is sticking and needs to be cleaned. With VEMS, that could be the problem too but it could also just be a VEMS TPS signal processing issue.

[A80Avant]

yes, i forgot to mention that, but this is posted in the aftermarket management section!

my ISV was a bit dirty and i cleaned it a little while ago, but it wont hurt rechecking!
thanks

[diesel des]

Adjusting the throttle damper fixed this for me.

[A80Avant]

yes that is my next move....

[A80Avant]

just tried it again today and it works nicely.

i adjusted the TPS slightly as well and idle is nice. I think this solves all of my idle problems as now the idle stays put with all electrics on (minus AC as it doesnt work atm) and is very stable.

yeah!

[A80Avant]

more news on this,

apparently the fuel cut feature with the kpa set to 30 was also having something to do with as the car was leaning out when pressing the clutch to go to neutral and didnt restabilize the fueling fast enough to keep the idle from dipping( car was still too lean from the fuel cut).

i used 0 value for the kpa fuel cut and only use the rpm fuel cut now and the problem seems to be solved completelly.

i do have a weird combination of ignition and IAC operation to control idle but it seems to be working nicely now, so in th future i may be trying out other stuff to see what works best.

[A80Avant]

update:

recently found a torn vaccum hose at the back of the inlet manifold which was related to higher idle speeds. Now rectified and idle speed is better and some of the idle settings needed to be changed.

However, i still get this weird issue: Once the IATs become higher with subsequently higher CLT, the idle speed becomes higher as well. I have disabled the feature that seems to elevate the idle speed according to CLT and i still get this thing happening.

To check, i disabled the ignition based idle and noticed that the idle speed climbs to 1150+ rpm without it, even if i keep the IAC DC at its lowest possible value( somewhere around 29) as anything below that, it starts bringing the idle speed even higher.

According to Gints, over at the vemsforum, the bosch IAC has a limb home mode whereas if the DC drops below 30% it acts the opposite way and the idle speed climbs instead of lowering. However at 30% according to him, the valve should be completely shut and the engine should die! Now most certainly, this is not happening with my engine!!!

any personal experiences with this one?

what is the DC that you have to set the idle valve in order for the engine idle rpm to drop to the point of the engine is about to die?

[diesel des]

40 to 50% duty on iac gives me a good idle.

[A80Avant]

on warm engine???

also do you have stock throttle valve size ?

and what hz on the valve?

[diesel des]

Have you opened the set screw at the throttle for more air. Check for air leak round injectors etc.

[diesel des]

Yea about 44% with warm engine and freq of 250hz I think. Stock aan intake throttle. Bypass screw never adjusted.

[A80Avant]

the screw is checked to make sure that the flap is completelly shut, yes.

how can i check for leaks from the injectors?should i pull them out?

[A80Avant]

yes that sounds about right for you.

it seems that i may be getting more air in from somewhere. either the TPS is not making a total seal, or i have to look at the injector seals.

the inlet had been removed to fit the phenolic spacer, but i dont think the injectors themselves were taken off..