RPM of my 1998 GT takes to fall, because someone knows what?
08-06-2008, 07:57 PM
#1
Thread Starter
Join Date: Aug 2008
Posts: 3
RPM of my 1998 GT takes to fall, because someone knows what?
My GT this with a problem, the rotation of the engine too slow to lower, accelerating this normal rotation but to return to idle about 5 seconds delay, because someone knows what? Or had a similar problem. I know that is not normal, because acelerei another car and spin the same year fell much more quickly. Thank you for your attention[/align][/align]
08-07-2008, 01:12 AM
#2
1st Gear Member
Join Date: Nov 2007
Location:
Posts: 143
RE: RPM of my 1998 GT takes to fall, because someone knows what?
I have a 96GT, and mine does that too it takes about 4 secs to return to a somewhat normal idle so I just decided to replace the whole top end because I could'nt find the problem. Try checking the IAC Valve, and the TPS sensor. If that doesn't work check for a vacum leak because our intake manifolds are known for cracking.
Good luck,
-Matt
Good luck,
-Matt
08-07-2008, 10:45 AM
#3
Thread Starter
Join Date: Aug 2008
Posts: 3
RE: RPM of my 1998 GT takes to fall, because someone knows what?
It took a year that replace the intake manifold, because it was leaving colant, put a model in which water is the line of metal, and the problem of the rotation continues, well, I will check the IAC valve and the sensor TPS, thank you for help .[/align]
08-07-2008, 11:03 AM
#4
6th Gear Member
Join Date: Mar 2007
Location: Slidell, Louisiana
Posts: 5,726
RE: RPM of my 1998 GT takes to fall, because someone knows what?
Welcome to the site, if I had to guess we don't have too many members from Japan.
Some people do what they call an IAC mod, which is a thin piece of metal the fits between the housing and the throttle body. The diameter of the hole is smaller and allows the rpms to drop faster. I tried it and wasn't impressed but many swear by it.
Some people do what they call an IAC mod, which is a thin piece of metal the fits between the housing and the throttle body. The diameter of the hole is smaller and allows the rpms to drop faster. I tried it and wasn't impressed but many swear by it.
12-01-2008, 09:42 PM
#7
6th Gear Member
Join Date: Oct 2006
Location: Texas
Posts: 10,551
12-02-2008, 09:56 AM
#8
2nd Gear Member
Join Date: Aug 2007
Location:
Posts: 427
mine does it also, 4-5 sec delay. I have checked and rechecked evrything replaced whole top of motor and still does it. my dads doesnt, bro inlaws moms doesnt and none of the other stangs I have seen on the street do it either. I have seen a hand full of us on this forum with the issue though. I was told it's a vacume leak by two engine builders but I cant find it. cost for them to find $500. I guess I can live with it for now but when I put turbo on I will want to resolve the issue.
12-02-2008, 01:01 PM
#9
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
It's the digital dashpot programmed into the tune. There are a number of functions and one scalar value associated with it and it can be tuned to drop faster by playing with these.
The Vehicle Speed vs. Lb/Min Airflow and RPM vs. Max Airflow functions control the maximum airflow allowed through the IAC at certain speeds and rpms, and the Dashpot settings function defines the commanded IAC airflow and various rpms. By reducing the allowed airflow values in these functions you can make it behave almost like a carbureted engine.
A related function Dashpot decay rate (which is very sensitive, make small changes) that controls the rate at which the IAC airflow is reduced by during the "dashpot" effect.
One last setting is Minimum MPH/Idle, a scalar value that defines vehicle speed at which the PCM will take over idle control. It is 5 mph in the stock tune, reducing it (I set mine to 2) will reduce the amount of time the idle is held high when stopping.
The Vehicle Speed vs. Lb/Min Airflow and RPM vs. Max Airflow functions control the maximum airflow allowed through the IAC at certain speeds and rpms, and the Dashpot settings function defines the commanded IAC airflow and various rpms. By reducing the allowed airflow values in these functions you can make it behave almost like a carbureted engine.
A related function Dashpot decay rate (which is very sensitive, make small changes) that controls the rate at which the IAC airflow is reduced by during the "dashpot" effect.
One last setting is Minimum MPH/Idle, a scalar value that defines vehicle speed at which the PCM will take over idle control. It is 5 mph in the stock tune, reducing it (I set mine to 2) will reduce the amount of time the idle is held high when stopping.
12-02-2008, 03:38 PM
#10
1st Gear Member
Join Date: Mar 2008
Location: Kadena Air Base, Okinawa, Japan
Posts: 85
It's the digital dashpot programmed into the tune. There are a number of functions and one scalar value associated with it and it can be tuned to drop faster by playing with these.
The Vehicle Speed vs. Lb/Min Airflow and RPM vs. Max Airflow functions control the maximum airflow allowed through the IAC at certain speeds and rpms, and the Dashpot settings function defines the commanded IAC airflow and various rpms. By reducing the allowed airflow values in these functions you can make it behave almost like a carbureted engine.
A related function Dashpot decay rate (which is very sensitive, make small changes) that controls the rate at which the IAC airflow is reduced by during the "dashpot" effect.
One last setting is Minimum MPH/Idle, a scalar value that defines vehicle speed at which the PCM will take over idle control. It is 5 mph in the stock tune, reducing it (I set mine to 2) will reduce the amount of time the idle is held high when stopping.
The Vehicle Speed vs. Lb/Min Airflow and RPM vs. Max Airflow functions control the maximum airflow allowed through the IAC at certain speeds and rpms, and the Dashpot settings function defines the commanded IAC airflow and various rpms. By reducing the allowed airflow values in these functions you can make it behave almost like a carbureted engine.
A related function Dashpot decay rate (which is very sensitive, make small changes) that controls the rate at which the IAC airflow is reduced by during the "dashpot" effect.
One last setting is Minimum MPH/Idle, a scalar value that defines vehicle speed at which the PCM will take over idle control. It is 5 mph in the stock tune, reducing it (I set mine to 2) will reduce the amount of time the idle is held high when stopping.