does vss have anything to do with idle?
12-12-2008, 03:26 PM
#1
does vss have anything to do with idle? my motor keeps dying when i come to a stop. and if i put it in nuetral sometimes that keeps it from dying but if i drive real slow like 1 mile an hour down my driveway it surges an wants to die.
i ask about the vss because if im rolling along and throw it in nuetral it idles fine but more than 50% of the time as i come to a stop the idle drops and when i finally stop it dies ?????
and this motor was tuned before i got it (by who i dont know) and i am planning on getting some tuning software.
i ask about the vss because if im rolling along and throw it in nuetral it idles fine but more than 50% of the time as i come to a stop the idle drops and when i finally stop it dies ?????
and this motor was tuned before i got it (by who i dont know) and i am planning on getting some tuning software.
12-12-2008, 03:35 PM
#2
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besides telling the pcm the car isnt moving no. it sounds like the tune isnt very good and def needs to be re-done. does the motor have h/c?
could be something stupid too like a vacumm leak
could be something stupid too like a vacumm leak
12-12-2008, 04:59 PM
#4
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well if you havent had the pcm tuned for this motor you def need to. and if it was done then they didnt tune the idle properly for the cam. what lsa does the cam have?
12-12-2008, 07:11 PM
#7
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Sounds like a tune issue to me also. It's pretty much expected to be something you have to work on with a cammed car. Some times even with just dyno tune this problem exists.
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12-12-2008, 08:10 PM
#8
i wonder if the speedo being off could have anything to do with this problem then. this stang has 355 gears in it and i dont know what was in my buddies t/a but my speedo is definetly off by about 10-15 miles an hour in a 55 zone keeping up with traffic it say 40-45mph.
12-13-2008, 12:09 PM
#11
crap = not working right or not working at all. There are decay tables that are broken down by mph. If the pcm is seeing an incorrect mph it will use incorrect decay/delay values and that can affect the idle.
12-13-2008, 12:20 PM
#12
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you need vss to properly tune the car.. i wasnt running vss on my ls2 notch and my idle was all over the place. it was dying on deceleration and acting funny... i had to keep playing with the throttle cracker in hp tuners to get it to keep idle and kinda fool the computer... i have the vss hooked up now and everything works great
12-13-2008, 02:58 PM
#13
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Both have and have not had a vss on the same car- 23x/24x cam 6.0 and it idles fine 850rpm- no P/N switch either. If you really wanna take the time it can be tuned.
Not that I know the exact controlls off the top of my head, but VSS and TPS should affect idle by having the car change a few values that affect idle-
Not that I know the exact controlls off the top of my head, but VSS and TPS should affect idle by having the car change a few values that affect idle-
12-14-2008, 10:34 PM
#14
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Classic symptoms.
For dying: Engine > Idle > Airflow > Min ETC (raise it)
For idle seeking: Engine > Airflow > dynamic > VE correction factor (more NEGATIVE)
Better get some software.
For dying: Engine > Idle > Airflow > Min ETC (raise it)
For idle seeking: Engine > Airflow > dynamic > VE correction factor (more NEGATIVE)
Better get some software.
12-15-2008, 10:25 PM
#15
one explanation for engine stall coming to a stop with no VSS.
no vehicle speed reported, PCM thinks it should control IDLE. When you let off the gas, if engine RPM is higher then target IDLE, the PCM will close the idle control motor trying to bring the RPM down, again it doesn't know you are moving.
When you come to a stop, the IAC is completely shut and doesn't open fast enough and engine stalls.
I even had the same issues with a Drive By Wire setup, 5.3L TH400. Engine would idle very low, around 400 rpm, for a few seconds before it would finally go back up to target 750 rpm. After I added a 15 pulse/rev sensor and got it programmed, all issues went away.
Throw a cam into the mix and it makes it worse. I had a 383 LT1, LT4 hot cam, etc and it would die every time I come to a stop, got VSS working and it stopped doing that.
no vehicle speed reported, PCM thinks it should control IDLE. When you let off the gas, if engine RPM is higher then target IDLE, the PCM will close the idle control motor trying to bring the RPM down, again it doesn't know you are moving.
When you come to a stop, the IAC is completely shut and doesn't open fast enough and engine stalls.
I even had the same issues with a Drive By Wire setup, 5.3L TH400. Engine would idle very low, around 400 rpm, for a few seconds before it would finally go back up to target 750 rpm. After I added a 15 pulse/rev sensor and got it programmed, all issues went away.
Throw a cam into the mix and it makes it worse. I had a 383 LT1, LT4 hot cam, etc and it would die every time I come to a stop, got VSS working and it stopped doing that.
12-16-2008, 07:45 AM
#16
My car has no VSS & it's fine. There are a few posts in addition to this one that explain most of where you need to look. Usually, IAC parked, IAC steps, IAC airflow, IAT & ECT spark, throttle cracker, are culprits. VE can be, but is less likely. The tuner most likely tuned WOT only, which would explain why the idle remains an issue. DIY tune using your own software is a good choice if you're willing to spend the time & learn. Good-luck
12-17-2008, 09:20 AM
#17
this may sound dumb...... but, do software programs come with any preset tunes (i.e. stock tnue or stage1 etc)?
the reason i ask is when i can buy this software i was thinking it would at least run better with the stock tune and i could go form there.
the reason i ask is when i can buy this software i was thinking it would at least run better with the stock tune and i could go form there.
12-17-2008, 01:42 PM
#18
You can request a stock tune w/ the purchase of the software or download a stock or even a reference modified tune from the LS1Tech (sticky) or software provider's tune repository.
