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Q: Can you please figure out what could be the problem so I can fix it?

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I was on my way out of town going 70mph and the speed limit was changing to 55mph so I put the clutch in and as soon as I did that the rpm shot right up to redline then down to 5000 and continued to do so as if I was revving. It would continue to do so until I slowed down to around 50-60mph or it would stop sometimes when I just take my foot of the clutch. Also when I'm using cruise control I tested to see what would happen if I pressed cancel without putting in the clutch pedal, giving any gas, or taking it out of gear. The rpm's stayed at around 3000 and the car would go forward and backwards on its own.

My car has 164665 miles.
My car has a manual transmission.

Check for any OBD-II diagnostic codes that may have set using a scan tool. There is an ECM update for this vehicle that addresses throttle position and control; although the TSB does not exactly match your reported difficulty if the update does pertain to your VIN you should still definitely do it in the course of diagnosing your issue. Typically, the RPM excursion you are describing is due to any one, or more, of the below listed causes. If you are not able to resolve it on your own, simply request an idle speed diagnostic - high speed excursions and the responding certified mechanic will pinpoint the cause.

Faulty Fuse: In the majority of vehicles, engine idle speed is controlled via an idle control valve (ICV). A faulty or blown fuse in other electronically controlled systems can cause the IAC motor to malfunction, leading to a higher than normal engine idle speed.

Faulty Idle Control Valve (ICV) and/or faulty mass airflow sensor: The job of the idle control valve is to maintain and control a consistent idle speed. The ICV will help counter any extra loads put on the engine such as lights, stereo and air conditioning. This part will often malfunction due to excessive carbon buildup in the intake manifold.

Vacuum Leak: On a fuel injected engine a vacuum leak will cause a high engine idle. The engine’s oxygen sensor(s) will detect the extra oxygen entering the engine via the vacuum leak which will alert the engine’s computer that the exhaust is running lean, which will prompt the computer to pump in additional fuel, resulting in an abnormally high speed.

Malfunctioning Throttle: A malfunctioning throttle system can cause both a high idle as well as an engine stall. A dirty air intake or cracked air intake tube is often the culprit.

Computer Malfunction: A computer malfunction can cause a high engine idle, especially the powertrain control computer. If it misinterprets the information it is receiving about the current engine speed, a high speed may be the result.

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