I recently bought one of Vijay's boost leak detectors and found a boost leak in the AAC unit, which I replaced. I've now driven far enough after reconnecting the battery for the idle to have dropped down to a proper level and now I'm looking to get it all set up properly.

 

Unfortunately the plastic on the connector to the AAC valve seems to be badly cracked and, while watching on the conzult, I could see that the AAC % value was hovering around 45% and then dropping to 0% for a fraction of a second, so replacing that is the first job, followed by setting the idle screw so that the AAC is around 15%!

 

At that point, the conzult idle setting screen was showing an idle of around 650rpm or so (that's with the idle screw adjusted to fully closed), but a few minutes later (after a bit of blipping the throttle and looking at the O2 sensor values) the idle on the same screen was showing around 950rpm. I take that to mean that I have a vacuum leak that gets worse as the engine gets hotter? Is there anything else it could be? :confused:

 

I've spent ages trying to check for boost leaks and I can't find any more. It still seems to me that I must have one as I can't get any pressure to register when I use Vijay's tester and I'm getting a lot less boost than I would expect for the welding tips I'm using. Is there anywhere where I could have a boost leak, but wouldn't be able to hear it all that easily?

 

I want to make sure everything is right before I install my boost controller! :hyper:

 

Thanks

The ECU controls the idle based on engine temperature.

 

up to 30 Celcius it should be around ~1200 rpm

between 30 and 85 Celcius it will drop to ~750 rpm

from 85 celcius and up, the idle RPM will start rising again up to ~ 1000RPM

 

maybe that explains your "problem" ?

 

-Eric

Ah. :o Never heard of that before. :nelson:

 

I'm pretty sure the temp didn't get as high as 85C, but I'm not 100% sure. Does the ECU still control the idle when you're in the conzult idle adjustment screen? :confused:

No, the idle adjustment screen overides the ECU control over idle, so idle should stay at a similar level...even after blipping the throttle.

 

although it sometimes takes some time for the idle to completely drop to base idle level again..

 

other things that can influence idle:

-throttle cable too tight

-incorrect TPS adjustment

-dirty throttle bodies

-faulty injectors or coilpacks (or connectors).