As some of you know I have been trying to learn how to fully control the PowerFC ignition settings at idle. There is a base programming that you can't edit with the datalogit software that adds a 10 degree split at idle and I have found that the engine idles better with little or no split at all. The only reason for it is emisions.

So after looking at my datalogit software, I remember that it only trys to control idle within like 200 or 400 rpm of idle .. so if you lower your idle speed down to a low number - say 400ish (lowest number you can enter with the commander) - the PowerFC won't try to control ignition timing and it will actually use the IGL and IGT map values. I played around with this some last night and got my vacuum up from 370 mmHg to 430 mmHg and the car idles much better. I also have a lightened flywheel - as topic in another thread. Even though I have done all that I would still occasionaly have my idle drop too far and bog. I'm not done tuning yet, but wanted to give others a heads up on what I found.

 

ok, so does the PFC actually try to lower your idle to 400??? If not did you keep the same idle? If you kept the same idle (rpm) what caused the vacume to change???

Thanks man, looks like you might be stumbling onto something

STEPHEN

 

Hey Stephen ... I'm not stumbling!

I put my old engine and new single turbo in my new car so everything was new. However I knew the engine was good and should be capable of a good idle with strong vacuum.

As you lower the idle speed you get into the PowerFC maps and at some point your idle will probably jump up to 1200 rpm. The engine will try to follow your adjustment to a lower idle speed, but it won't ... at least it didn't on mine. If nothing else turn the motor off and then fire it up after you make the change. At this point it is reading directly from your PowerFC maps.

 

Hey Carson my idle was fine but when driving VERY slow like in reverse out my drive way its rough.....

anyway, I did what you were talking about then pulled some fuel out of my maps in the idle area up to about 1200 rpms and it seems to have smoothed out alot.

I'll keep driving it a while and see how it does for a week or so

Later,
STEPHEN

 

You can play with fuel and timing to get the idle back down to like 900 rpm.

 

I've got it at 1000 right now and I'm ok with that. What did you do to lower it? Pull more fuel or what? I might try to get it down a little lower.

 

Carson,

While doing this, have you tried discounecting the ISC solenoid? You probalby will have to manually add more idle air since the ISC solenoid is one way the ECU controls idle speed.

 

No I didn't bother to unplug the ISC. I adjusted the throttle screw. I also run my timing right around 10 degrees. I'm still playing with it too. I don't quite have all the water temp correction factors setup correctly yet so it doesn't like cold starts!

 

Im still dialing in the idle, here is what has happened so far. it hunted up and down from 600 to 1200 like mad when i first hooked up the PFC . So, i messed with the idle set screw and the air bleed screw and got it to behave better but it is still not perfect. Now, when i sart it,it runs for 5 seconds then quits. it take 3 tries usually to get it to run and ineed to tapp the accelerator pedal for a minute to keep it running. it then smooths out but it still needs adjustment. Any ideas ?
thanks all.
1R1

 

Usually when the idle hunts high than low, it is caused by too much air. This can be caused by a number of factors including intake air leaks around gaskets.

On my engine(rebuilt last spring); I have the throttle set screw out so that it does not even touch the stop plate.
The air bleed screw(bottom right of the throttle body) is out only 1/4 turn.

Also: make sure that the throttle cable is loose enough to allow complete closure of the throttle; and make sure the secondary throttle set screw allows it to be fully closed at idle.

 

as usual Chuck you are one or two steps ahead of me and everybody else. I havent messed with the secondary throttle set screw. Ill try that when i get home this weekend. If i remember correctly, my air bleed screw is out about 1 full turn and the idle screw is just touching the stop plate. but i do rember backing it off alot to get the idle better.
thanks
1R1

 

Just remmebered something, I think im still running rich.
I get a good puff of blueish smoke on the upshit when pushing the car hard. anybody have this happen to them ?
1R1

 

Another posibility that has happened to some others; is dirt or carbon build up in the ISC solenoid valve. Remove the ISC solenoid and clean it well with something like CRC (black and red can) brake cleaner.

Submerse the valve end into some cleaner and with 6 to 12 volts, click it open a few times as well.

 

Good idea Chuck, Ill try that too, i also have an extra ISC so i can swap to see if it changes
thanks

 

I have a question for you guys. My car idles very smoothly at 850 RPM normally but, when I turn on the AC it stubles all over its self and comes very close to dying. Anyone have any ideas as to why this may be?

 

spyfish,

all that stuff about low idle adn being able to manually adjust the timing is uneccesary. just switch off teh idle ign control with PFC, that is the function that control idle with varibale timing.

You may already know that, but seemd liek ti twoudl help with what you tried to do.

 

Yeah, but have you looked at the timing when you turn off the ign-idle control? It is at -5/-15 with no AC or EL! That just doesn't work for me. I want around 10 degrees and no split. I want control over it. I might even run an entirely different ignition setup.

 

can't one just adjust then with the maps when the ign ctr is off?

 

No, the idle ignition is still locked via hard programming. You can turn off the control and see for yourself. There are three different programmings depending on base, E/L, & AC.

 

hey carson,

this is off subject, but im getting my 94 back together and am gonna need the pfc help we were talking about. i got a datalogit, too. im not real sure on what to use as it has no instructions, but ill talk to you later.

 

rotorbrain - the Datalogit should have Instructions.PDF in the root directory of the CDROM. You'll need Adobe Acrobat to open them, free download from www.adobe.com.

K

 

i know about the instructions. id just like to hear some experience. i just dont have the money to just try anything that i think of. if it is too much of a time consumer then ill just have to deal with it right. haha. its just that the whole "total programming ability" thing is new to me and i just want to get good at it and get some pointers on the way, haha.