RPMs too high


Old 09-17-11, 10:43 AM
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RPMs too high

My car's tachometer is going up much higher than it used to, and it is eating up gas. The RPM's are too high whether driving or idling. Occassionally, the problem will go away for a day or two, then return. I know I need to change my battery because the voltage is a little weak. A while ago, the Throttle Position Sensor went off but turned off after 1 day. The error message has not returned in a long time. Any suggestions on what I should replace other than the battery?

2000 Oldsmobile Alero, 6-cylinder
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Old 09-17-11, 10:55 AM
chandler's Avatar
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Welcome to the forums! The battery will only cause you to wake up one morning and not be able to go to work, by not starting the car. Once the car is started, the combination of the alternator and battery will power everything, regardless of the battery's condition. Now, if your alternator is going south, your could be replacing it soon. Have you had it checked lately? Have you run codes on the car? Go to an AutoZone or other parts house. They will usually run the codes for you for free. How do you know the throttle position sensor "went off"? Do you mean the code showed up? Did you reset the codes? I would start by replacing the air filter, as it could have adverse affects on engine performance, and fuel mileage.
Old 09-17-11, 12:18 PM
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1. air leak somewhere, including loose air filter hose, PCV, etc. whatever can feed extra air into the intake/engine
2. idle speed control unit, applicable to your make and model, is not working right
3. ECU thinks your engine is running low on RPMs and jags them up; this can be caused by various sensors malfunction, anywhere from coolant temp one through throttle and cam ones
4. mechanical damage to throttle cable; maybe debris stuck somewhere, or rust; would have been nice, easy fix
5. vacuum leak or malfunction; listen for hissing or check on all vacuum lines.

Symptom: The engine idles too fast. After the engine has run long enough to be warm, the idle speed does not come down to normal. You really notice it when you come to a stop and must have to push hard on the brake pedal to keep the car from moving.

Possible causes:

If you have a carburetor, you may have a bad accelerator pump or power circuit.
The Fix: Replace accelerator pump or replace carburetor.
The engine may be overheating.
The Fix: Check and repair cooling system.
The fuel pressure regulator may be operating at too low a pressure.
The Fix: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (Generally not a DIY job)
The ignition timing may be set wrong.
The Fix: Adjust ignition timing.
There may be some type of ignition problem.
The Fix: Check and replace distributor cap, rotor, ignition wires and spark plugs.
There may be a fault in the computerized engine control system.
The Fix: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (Generally not a DIY job)
There may be a vacuum leak.
The Fix: Check and replace vacuum lines as required.
You have a bad idle speed control unit.
The Fix: Replace idle speed control unit.
The alternator may not be working properly.
The Fix: Replace alternator.

just like chandler said. read codes. if none present, let us know.

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