RPM TOO LOW AND DYING WHEN LETTING OFF THE GAS

TURBO200R4 said:

just my opinion and i am not going to argue
i have seen cars come in that the throttle plates/shaft was worn.
on these vehicles i was able to reset the throttles back to where they belong by turning the screw slightly so it would bring up the idle to where the tps was correct. for example if the tps was suppose to be .6 and it read .53 i would turn the idle screw till the tps read .6
jmo i think that the stepper motor with the ign on comes out to a fixed position and stays there. i think that it never moves or adjusts. now if some one wants to prove me wrong all they have to do is watch the tps voltage when it is gaining and losing rpm.
now i think that fred is correct that u can set it a little higher. if i wanted to set it higher i would first try to set the stepper motor a little higher before i messed with the throttle plate adjustment screw.

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rng3 said:

I believe one of the differences is that on the cars I have worked on there is a separate Air Idle Control, often a stepper motor and a small valve that allows additional air past the throttle body to control the idle speed. The throttle plates themselves do not move.
On the Rocket it looks like the idle control actually moves throttle plates themselves to control the idle.
Good point on watching the TPS voltage during the idle hunting.

Rick

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TURBO200R4 said:

i guess i forgot my point
if the stepper motor does go out to a fixed point and stay there then when u returned the throttle there would be no way for it to shut off the air supply to cause a problem.

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Rocket Scientist said:

I can't speak for anyone else's, I've only ever looked at mine, but when I'm hooked up to Tuneecu, when I open the throttle slightly, my stepper backs off, because it thinks the idle is to high. The longer your on throttle, the farther it backs off. When you close the throttle, it goes back to the stop screw, and what I call the "base idle speed". If the base idle speed is to low, the throttle plates close to far and choke off the air until the stepper can get them back open, which takes a few seconds. During the time the plates were closed to far on mine, it would buck and run rough and then eventually get back up to the normal idle speed. I never unbolted my stepper to check, but I would guess my idle screw probably keeps it at about 600-700 rpms.

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