1997 Saturn RPM

Tiny
HERTWIG
  • MEMBER
  • 1997 SATURN SL1
  • 4 CYL
  • FWD
  • MANUAL
  • 168,000 MILES
97 SL1 saturn 5 speed rpm goes up when car is moving also goes up when shifting between gears. Rpm does not raise when car is parked or stopped what is the cause.
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Friday, January 28th, 2011 AT 10:35 PM

5 Replies

Tiny
SATURNTECH9
  • EXPERT
I'm confused the rpm's go up when your driving especially when you have a stick.A little more detail's please.
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Friday, January 28th, 2011 AT 10:59 PM
Tiny
HERTWIG
  • MEMBER
I start car, idles fine at about 800 rpm. Push on gas pedal while in netural (5 speed) parked, rpm drops down to 800 right away. Everything is good so far. When driving and shifting between all gears, rpm will go up about 300,400 rpm more, when clutch pedal is pushed down while car is moving. Also when I roll to a stop coming to a stop sign rpm will stay at about 1500 rpm for about 8 seconds, than go down to 800 rpm. As long as I stay parked or not moving rpm works fine, drops down to 800 rpm right away. Service engine light does not come on. Only when moving does the rpm seem to raise some what, maybe something do to with transmission speed sensor if there is such a thing.I hope this explains it. HELP THANKS
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Saturday, January 29th, 2011 AT 3:33 PM
Tiny
SATURNTECH9
  • EXPERT
If the rpm's go up while moving that's normal on a stick shift the rpm's get kicked up otherwise when you let off the gas to shift the rpm's would drop too low. Here is a description of the iac.
GENERAL DESCRIPTION

The PCM controls engine idle speed by controlling current to two stepper coils contained within the idle air control valve assembly.

The PCM controls a two-coil stepper motor, which controls the bypass air intake into the throttle body, to decrease or increase engine idle speed. The motor allows air to bypass the throttle plate and enter the intake manifold. The determination of how much air is allowed to enter the engine is based on current engine speed, A/C compressor operation (On/Off), coolant temperature, throttle position or if the transaxle controller requests greater engine torque during power-off downshifts (automatic trans axle vehicles only). The PCM/TC will also use the Idle Air Control (IAC) Motor to control coast down shifts.

IDLE AIR CONTROL SYSTEM

The purpose of the idle air control system is to control engine idle speed, while compensating for changes in engine load.

The idle air control (IAC) valve, mounted in the throttle body, controls bypass air around the throttle plate. By moving a conical valve, called a pintle, in towards the seat will decrease airflow. If the pintle is moved outwards from the seat a controlled amount of air is allowed to bypass the throttle plate. If the PCM determines that rpm is too low, more air is allowed to bypass the throttle to increase rpm. If rpm is too high, less air is allowed to bypass the throttle plate decreasing rpm.

During idle, the proper position of the IAC valve is calculated by the PCM, based on battery voltage, coolant temperature, engine load and engine rpm. If the rpm drops below specification and the throttle valve is closed, the PCM moves the IAC valve to control speed.

Once the PCM has sought a desired idle it can retard or advance spark timing to smooth the idle out in slight changes. This operation keeps the IAC valve from continuously moving in and out. The PCM will learn the IAC position for both A/C and non-A/C operations. These values can be displayed using a Scan tool.

An unstable TP sensor at idle, varying more than four counts (TP counts read on Scan tool), will disrupt closed loop engine idle control.
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Monday, January 31st, 2011 AT 4:24 AM
Tiny
HERTWIG
  • MEMBER
Damm! Your smart and knowageable, this explains alot. Talked to alot of mancanics they could not give me an answer THANKS VERY MUCH!
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Wednesday, February 2nd, 2011 AT 12:00 AM
Tiny
SATURNTECH9
  • EXPERT
Your welcome let me know if you have anymore question's or problem's.
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Wednesday, February 2nd, 2011 AT 3:56 AM

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