Saturn Fast Idle

Verifying proper sensor operation with a scan tool is the best start but if you don't have one of those then look for vacuum lines that have been eaten by squirrels. Vacuum leaks can be revealed by spraying around the lines with carb cleaner and listen for an RPM rise from the engine suddenly seeing a new burst of fuel.

You can also try removing the air filter assembly, and spraying short blasts of throttle body cleaner into the air inlet.

There is a system designed to bypass the throttle body to adjust the engine speed while at idle. If this system has become gummed up, spraying with cleaner will provide a temporary cure, as well as diagnosing the problem. If the spray allows the idle to return to normal, have the throttle body cleaned properly.

If it's a transmission with a vacuum line to the inlet manifold, it may have become dislodged when the "hard hit" occurred. Additional air from an open vacuum line will often cause a fast idle.

At least some GM cars (don't know specifically about Saturn) had an "Idle Control Motor" that was mounted to the throttle body (an electric motor, working through a lead screw if I recall properly, but it HAS been a while). It could be seen wit the entire air cleaner and lower housing off the top of the throttle body; identifiable by the wires leading to it. It could go into a mode where it attempted to drive the control all the way to one end of travel, resulting in such a problem as you describe. I no longer have an address for the mechanic I knew who was correcting the problem on a friend's car (my exposure to it), or I'd ask him what he had to do. I know that he had to power the motor to run it back into the correct range so that it correctly self-adjusted, but I think that there was some additional "fix" needed. Whole job took him maybe 15 minutes including remove-and-replace for the air cleaner housing. A mechanic familiar with GM cars of the era may be able to do the same for you.

Google "GM idle control motor throttle body" or "GM idle air control throttle body". Several forums have threads; they describe it as a four-wire stepper motor, and say it is possible for it to get gummed up (long tapered shaft should withdraw from throttle body during operation; clean it and the hole it goes into). See http://67-72chevytrucks.com/vboard/showthread.php?t=337695 for example, especially post #12. [Despite name of forum, '90 Suburban involved.] Rock Auto's online catalog (http://www.rockauto.com/catalog/raframecatalog.php?a=G-GM) shows the idle air control valve for a 1994 Saturn (I tried the "SC" series, 1.9L w/TBI). Brand new part runs $30 - $56 depending upon brand.

I had the same problem with a 2001 PRIZM and was told to remove the battery cables and let sit for about 15 minutes then put back on this somehow reset the computer and it works fine now it's been almost a year and still ticking along

Be advised - there is a Mass Airflow sensor in the path of the air intake at the throttle body. You do not want to get any typical intake spray cleaner on this sensor as it will remove a coating that prevents sludge buildup on the the sensor. There is a speciality cleaner designed for work around this sensor available at most auto parts stores.

I own two 1995 Saturn's and find the throttle body assemblies very susceptible to becoming "gummed" up, causing all sorts of running problems, including fast idle. Cleaning with the off the shelf cleaner from the auto parts store has kept both cars running from purchase thru today.

On my daughter's SL, with the same symptoms, it was a leaking intake manifold gasket. the gasket crumbled to pieces when I took it off. But do check the easier fixes first. ie- vacuum lines, or the Idle Air Motor.

good luck

Rick

I would suggest you do a diagnostic scan first. It could be a bad IAC (Idle Air Control) valve or a vacuum leak. A service manual from a local auto parts store would be a good investment. These typically have a diagnostic section that should walk you through testing the IAC valve. There is usually some help on how to trouble shoot different problems. Chances are it is either the IAC valve or a vacuum leak. Good luck.