TrinaBabe

iTrader: (3)

I went from a decent idle to pretty much no idle in a day. I had the stock turbo set-up with stock injectors. 272/272, FMIC, Upper/Lower IC Pipes, stock intake pipe, open air filter, sheetmetal intake, 3" turboback exhaust, Adjustable fuel pressure regulator, and an AFC. I just added headers, o2 housing, GT35R, new lower IC piping, intake piping, and 780cc injectors. Now the idle blows donkey. It BARELY will hold at between 500-1000 rpm if I SLOWLY let off the gas and let it pick up the idle. If I just straight let off the gas it will die 90% of the time.

I hear other people are having no problems with the 780cc injectors holding idle fine. Could it be the ECU is still trying to map out the new fuel trims and is just taking a while? I had to lean out the AFC to -36% or so across the board... is this pulling too much air flow confusing the ECU too much to compensate? Should i try raising the idle, lowering the fuel pressure, and just run it for a day and see if the idle gets any better?

Any ideas would be helpful! Thanks guys

GTVEVO

iTrader: (22)

Man since you are only running an AFC the only thing I would know to try would be to adjust the bliss screw on the throtle body (worth a shot, just mark the spot so you can put it back if it doesn't do any good). It shouldn't take much one way or the other but you are probably just alittle bit to lean during idle due to the -36 being marked on the AFC if the AFC is set low throttle to zero. Otherwise the ECU isn't even looking at it and it is just to lean altogether.

You best bet might be to get the ECU flashed for some better idle control or puchase a blow through maf or Standalone. Sucks to just say spend more money, more money but you look to be set well so far so you might as well go ahead and finish it.

Good luck man.

jj_008

iTrader: (8)

You may need to go to smaller injectors for the MAF. I use 680cc w/ my GT30R and my idle is perfect w/ the stock MAF. I am using an XEDE/XEDEflash.

MayhemSi

iTrader: (2)

Though I don't endorse it as the correct way to do things, you can always run two afcs..

TrinaBabe

iTrader: (3)

Anyone else? Running 2 AFCs wont help. The reason I am thinking it might be idling bad is because the dead time on the injectors. The AFC being leaned out to -36% would be the correct fuel adjustment but it is cheating the ECU into thinking it has less air than it does. I can't really see any reason for the idle to be too bad except the dead time on the injectors. Any other ideas?

rlazer5000

iTrader: (16)

Im just taking a guess, but could u have some kind of leak? U mentioned u installed a whole bunch of new parts, so maybe there could be leak of some sort. How long have u had this problem?

MalibuJack

iTrader: (5)

Those injectors are just way too big to try to adjust with the S-AFC.. Your right about the dead time, your either getting all or nothing when it comes to fueling which means its going to be difficult to get a smooth idle..

You may have to manually adjust your idle so its around 1000rpm, that should keep the airflow up high enough that the fuel demand is a little higher, then you can adjust your S-AFC to around -40% (Probably something around 12hz at idle) any lower and your likely swinging into open loop and startup fueling parameters..

TrinaBabe

iTrader: (3)

I figured as much. I figured the ECU said give some gas, then it flooded it so it said cut the gas and it choked. Resulting in ridiculously bad idle issues. So how do I adjust the idle? Sounds stupid but I know on DSM's you had to ground a little connector on the firewall. Do I just turn the screw or do I need to ground something or what? Also, should I remove the fuel pressure solenoid? I believe it's only purpose it for startup. I wouldn't see how that could help unless it is overfueling when the idle dips low enough. Thanks Malibu Informative as ever!

MalibuJack

iTrader: (5)

I think you need to try to force open loop, so you can bump the idle.. There's an adjustment on the throttlebody near the idle speed solenoid, there's not alot of adjustment so don't force it, but it should give you a few hundred RPM's of help..

Not sure what to do to help the dead time though... its "Sluggishness" is just a factor of its size and internal solenoid.. so you have 1% on time, but you have two problems.. 1% due to dead time isnt 1%, but its still more than stock.. when you go lower, you get less fuel, when you get higher, you just flood it..

The big problem is the closed loop fueling trying to hunt for the idle.. you have the triple whammy.. Big injectors, big cams, and big turbo.. all affect idle in some way.. the first thing oyu need to do is get the airflow through the maf a bit higher.. so you will need to get your idle up.. then you need to get your MAF to reading to be more stable (not sure how you will do that with an s-afc though) but if you can get your MAF reading fairly steady, it will help the quality of idle alot.. Then you can focus on altering your fuel trims for the injectors.. on an OBD-II scanner, look at your long term and short term trims.. If its -20% it means its 20% too rich, so you have to remove some portion more fuel (unfortunately your limited with how much signal you can remove at idle, stock engines idle at 30-40hz, your probably a little lower, and you can't go much lower than 12hz)
I'm not aware of any grounding trick for the evo's idle.. but you can help things with some minor adjustments.

Hope this helps..

MalibuJack

iTrader: (5)

Also check for the obvious vacuum and boost leaks too.. That might help a little to find a few leaks..

11secEVO7

iTrader: (37)

i basically have the same setup...
272's,GT35R,750cc injectors..
My afc is set around -18 or so...for 1000-2000rpms..
idle isnt the best..but it doesnt cut off.
u may have a leak somewhere..

evo 8 ya

iTrader: (31)

Go easy on the car untill you get a reflash or some kind of tuning. With the AFC that far in the negetives the ECU is advancing the engine timing because the AFC has "tricked" the air flow meter in to thinking there isn't that much air going into the engine. Baby it untill it's tuned.

TrinaBabe

iTrader: (3)

I do need to check for leaks. I did it before the turbo and everything was ok aside from a large leak on the BOV flange. I got that fixed but it still idled ok (Died SOMETIMES) even with an audible leak from the bov. When I had the Sheetmetal, intercooler and piping and the cams it was ok. After the turbo, intake pipe and injectors is where it started to get horrid. The AFC reading on the hertz is around 40 but then I am taking away 36% of that which brings it around 25-26 that the ECU sees. That should be ok. The idle was never raised so I am sure that will help. I just know on DSM's the ECU will fight any adjustment you make unless you ground the do-hicky on the firewall (I think the same one you ground to adjust the base timing). I guess I will just do my best and try to raise the idle and check for leaks and go from there.

My other question I guess is who else could i get to reflash the ECU to simply lower the fuel trims and nothing else. I dont want to pay $200 or more for a reflash. I will buy either a stand alone or get something like the ECU plus later but for now I do realize that my timing is crap. I talked to Dynoflash about it and he told me $80 but now I cant get ahold of him. I have tried two times this week with nothing back yet. Can turbotrix or someone else do it for?

rlazer5000

iTrader: (16)

^^ they coould both do it, i guess its more of if the price is right. Try sending both of them a pm and have them quote u how much its gonna cost. Sorry to go off topic, but did u install all ur mods urself?

evo 8 ya

iTrader: (31)

I would at least get a reflash. Even if it's $200 it'll be alot cheaper than $2500 for a new shortblock.
Al "Dynoflash" is a busy guy and he will get back to you as soon as he gets a chance.