Ok... I know there is another post on here that is similar to this one, but the help in there doesn't fix my issue... i've replaced the TPS sensor AND the IAC, to no avail. I know the IAT sensor is bad, but waiting on AGP for a new one, but I do not think that it is the problem...
The idle at start up is very rough and sporadic. Sometimes the car will start, turn over a couple of times and shut off, but it will always start up again after that and "idle". About 9 times out of 10, the idle is horrible... watching the tps voltage, you can see it go from 0.82/0.83 (the base read on the sensor when car is 'on' but not running) down to 0.64 and then up to 0.99 (at which point, the rpms follow in suit... from 1000 down to 600ish up to 1300). It seems sporadic when it does that, but is also seems to follow a pattern. Typically if you do not let it sit for a minute or two idling, if you try to hit the throttle, the car will either die, or will try to die, and you have to feather the throttle until it behaves normally. The idle problem will persist as you drive around (if sitting at a light, or if you shift out of gear), but will typically go away after about 20-30 minutes of driving. Sometimes the car starts up perfectly fine and idles like a champ, but like I mentioned earlier, that is the case about 1 out of 10 times. I have a data logged idle session if that would help out. Here is the parts list on the vehicle (stock cams on car):
Block bored 0.040"; 2.5L from 2.4L
Eagle H-beam Rods
JE Forged Pistons 0.040" over, 8:1 Compression, and DCR modified
Windage tray + crank scraper + baffle replacing the balancing shafts
Ceramic Coated, port and polished cylinder (NRGY)
Manley stainless steel valvetrain with 2.7L rocker arms (I think Mopar calls them lash adjusters... something stupid)
Ceramic Coated rod and main bearings
DCR Billet Steel Crank strap kit
Ceramic and Teflon coated, port and polished intake manifold
AGP 3" Intake
AGP 2.5" cold and hot pipes with AGP front mount intercooler
Accufab fuel pressure regulator with return line
AEM EMS
Boomba Fuel Rail
Deatschwerks Stage 2 injectors
Ported exhaust manifold and compressor housing on stock 16g turbo (TD04)
Borla 2.75" exhaust
PLX Devices M-series wideband going to the AEM EMS
AEM UEGO gauge in the pillar pod
DCR Modified Oil Pump
DCR Big Filter Kit
DCR Pick up Tube
DCR Oil Flow Modified
AGP Intake Air Temp sensor
PTP 55mm Throttle Body
AGP Oil catchcan with check valve
Walboro 255lph fuel pump with bottle neck delete and modified cage
Forward Motion wastegate with Hallman MBC
HKS SSQV (replacing with Synapse)
MSD Coilpack with MSD wires and NGK Iridium plugs
BWoody Coilpack Heatshield
Autowerks strut tower bar
ACT Flywheel + Clutch drag kit
Billet 2-3 shift fork
Fuel Pressure is set to 38 psi... car runs lean at idle (between 16 and 17) and the AEM UEGO goes --- when the TPS dips off (the EMS says the PLX reads around 21.x during this time; and yes, the UEGO and the PLX read identical numbers). If you have any ideas and/or advice, they will be greatly appreciated.
sounds like your car is hunting
there are a couple ways to get it to idle good, unfortunatly there are many parameters and if you hit up the wrong one it could take a long time to undo the mess up
BUT what i would start off with is
#1 start enrichment bring it up (start with 10% and keep adding untill it starts easy)
#2 start IGN advance make sure it is in the negative (-2 or something) this will prevent the starter from straining and "kick backs"
#3 the fuel map get it as close as possible (sometimes you will need to move the Y (rpm's) so you can get it in the bulls eye make sure the next lowest rpm and load are also set very close
#4 idle feed back rate lowering the feedback rate (actually raising the number) could eliminate the over shoot (up and down hunting)
#5 double check for vacume leaks in the TB and intake mani (juss do it)
there are many more variables BUT you were very vauge with your description (yet you listed all mods in extream detail)
please post up a current map and log of your idle (w/ the idle parameters on your screen) this will help people help you
please post up a current map and log of your idle (w/ the idle parameters on your screen) this will help people help you
Here you go and thanks for the advice. I listed the mods in detail in case anyone saw anything important in them (my Turbo T/A, like all Grand Nationals, suffer from specific issues that can be caused by almost any of the mods... so I made sure I didn't hold back :P besides, I had just given a list to a friend of mine and thought about posting here, so it was cut-and-paste hence why some of the items really were useless to post).
subscribed. my car does the exact same thing. also have constant small idle fluctuations after reaching operating temp. jay tuned the car and suggested i move the wideband to the upstream position... didn't help.
I believed you, lol. Guess something messed them up... not sure. The idle log is for the AEMLog program, of course, so that you can see the whole thing. A bee was sitting pretty mean on my driver seat, so I let it idle and log for a while before it flew off.
I believed you, lol. Guess something messed them up... not sure. The idle log is for the AEMLog program, of course, so that you can see the whole thing. A bee was sitting pretty mean on my driver seat, so I let it idle and log for a while before it flew off.
I didn't feel like taking an epinephrine shot and spending the night in the hospital How do I add the files so that you can get them?
1.19 files you can attach to a post (advanced post) and the log files you will need to zip and then attach em ...if ya have trouble you can e-mail them to me and i can post em up for ya
try to log another idle log(make sure your tune parameters are showing on the screen or they will not log)
your crank advance is at +10 try to make it -2 (always a negative)
and your start enrichment could go up to 120 raw (you are at 102)
other than that it seems you are relying on ign. to stabalize the idle (and 10* is allot) try to use a little fuel too (so when letting out the clutch it dosnt go lean)
try to log another idle log(make sure your tune parameters are showing on the screen or they will not log)
your crank advance is at +10 try to make it -2 (always a negative)
and your start enrichment could go up to 120 raw (you are at 102)
other than that it seems you are relying on ign. to stabalize the idle (and 10* is allot) try to use a little fuel too (so when letting out the clutch it dosnt go lean)
Crank Advance at +10 actually started the car without an issue. At -2 it would take 20 seconds sometimes for the car to start. At +10 it would start the second you turned the key. I tried giving it more fuel (lowered it to about 14ish AFR at idle) but it still had the same issue. Will try some more enrichment and see how it goes.
My car never wanted to idle nice till it got between 12 and 13.......... Hope you get yours fixed... hate when it idles like ass, everyone thinks your driving a honda.lol
__________________
The Cobalt firmly grabs you and whisks you along your way instantly.
It does so with authority and poise, but while slipping relatively unnoticed through traffic,
never being violent, or dare I say it, frightening. When you ask the SRT-4 to take you somewhere fast,
it punches you in the face, throws you over its shoulder, and runs, screaming,
so quickly that its tires can barely keep up
some things i do is to re-do my breakpoints for the lowest rpm (i set it for about 400 just where my low idle is set to) this will allow for a much more stable idle, i also follow the instructions in the manuel and start at 900 and go up every 50 rpm until my IAC map is very close to dead on,and get the base fuel and ign timing close to perfect and i let the EMS do the work for me
all engine combos will differ but below is a copy of a map that has worked and will give you an idea
and i use allot of timing down low , it helps build vac (for me)
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Major Idle Issue; need help
and thanks for the advice. I listed the mods in detail in case anyone saw anything important in them (my Turbo T/A, like all Grand Nationals, suffer from specific issues that can be caused by almost any of the mods... so I made sure I didn't hold back :P besides, I had just given a list to a friend of mine and thought about posting here, so it was cut-and-paste hence why some of the items really were useless to post).
How do I add the files so that you can get them?
try to make it -2 (always a negative)
, it helps build vac (for me)
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