GoCarSc300

iTrader: (1)

Here's what previously happened:
Ok, to make a long story as short as possible my car (97 SC300 5speed) was recently in the shop getting a boostlogic turbo kit installed. Everything was cool and then after the dyno we took it on a few street runs. At first it was good, but then with the next few street runs it would go all the way down to 0rpm when coming down out of boost and stall out. We tried adjusting engine parameters on the AEM EMS, but it didn't help. We experimented with unplugging the idle control valve(ICV) and setting the idle on the EMS and it worked just fine coming off of boost. Since I know my ICV is bad I want to replace it...

Here's the problem now:
The car is doing the same thing and I just paid $400 for a brand new ICV from Lexus! What else could it be?

Hints/Possiblities I've thought of:
Something is wrong with my setup because my BOV is vented to the atmosphere? I don't know...Please help I want my car back!!!

574-SC300

With a mass airflow sensor, the MAF reads all the air that goes into the turbo then the engine. so it knows how much fuel to add. If you vent your BOV to the atmosphere you have extra fuel because it thinks air is there, thatcould be why you can get stalling and sputtering after a blowoff when slowing down. I'm sure EMS should be able to compensate for venting to the atmosphere or you can just reroute it back into the intake after the maf.

motorheaddown

There are way too many issues and unknowns here.

First, I don't understand how you came to the conclusion that the IACV was faulty to begin with. When it was unplugged, the EMS can't control the stepper motor of the valve. If it ran better, it's because the bypass air it was letting through was enough for it to catch idle when coming off boost.

FWIW, you can always tell if the IACV is working when it's connected to the AEM. The EMS parks it in a known location after the motor shuts off. You should hear two series of clicks a couple of seconds after key "off". You could also just set key "on" (not start) and change the idle setting through the EMS with the IACV removed but connected to the harness. You should see the plunger move a little bit.

It sounds to me like nothing more than a tuning issue. Basically, it's not catching the idle feedback loop during engine decel. What are your idle AFRs and timing? Is wideband feedback invoked? What's the idle learned value when it's idling ok.

I suggest logging all parameters associated with idle when making a pull and then see what happens to fuel, timing, IACV control, etc., during engine deceleration.

-scott

GoCarSc300

iTrader: (1)

574-SC300: I am not running a MAF setup. I have converted it to the speed density setup with a 3.5 bar map mensor and an AIT sensor from AEM. I did this so that the MAF decell air problem wouldn't occur, but just my luck, it happened anyway. This is so frustrating!

GoCarSc300

iTrader: (1)

Motorheaddown: my tuner has tried all of the tuning parameters that are related to this problem and has troubleshooted over and over with no success. He's even called some other AEM EMS master tuners and their suggestions have not helped either. I'll tell him about your ideas and see if he can get something out of it. Thanks for the help.

GoCarSc300

iTrader: (1)

Here's an update:
1) after the cvar is taken up into boost and you let off, the needle is dropping down in rpms as usual but then it breaks through idle and goes to almost 0 and stalls out. the wierd thing is that it doesn't do this if you unplug the idle control valve (which i just replaced thinking that was the problem)
2) the brand new AEM Tru Boost controller I got isn't functioning properly because we can't make more than 6.5lbs of boost so tomorow we're gonna pressure test the system and try to identify a leak that might be responsible for both problems (I really hope its an easy fix that we identify tomorrow cuz I want my car back with more boost!)

dumdumgreg

iTrader: (5)

just curious, what did you finally do to fix this?