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Car racing and slowing, racing and slowing in neutral and park

(1990 Honda Accord)
in Schenectady, NY on March 29, 2010
WHY DOES MY 1990 Honda Accord engine keep racing and then slowing down and racing and slowing down only when in neutral or park? Car runs fine while in drive.
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Popular Answer
First check the coolant level low coolant level can cause this. Second the coolant temperature switch that reports engine coolant temperature to the computer can cause this symptom if the switch is failing. Third the idle control and fast idle control device if they are experiencing a problem can cause this. If the surge is really high and low the computer can be going into "fuel cut mode" where it cuts fuel until it can take control of the idle speed, this system can malfunction if the engine has a bad vacuum leak and the computer does not have the capability of controlling the idle speed. Basic diagnostic tests are needed to figure out the problem. Autozone have some popular workshop manuals for free on line once you register (for free) on their website .There is a company that independent auto repair shops "buy" their information from that offer a very reasonable service to do it yourselvers. You get a one year subscription to year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... great quality information same as the professionals have ,much better than generic workshop manuals from parts stores, much cheaper than the factory manual. or try and get an online repair manual subscription.
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on December 17, 2010
I think it is the TPS. I could be wrong but just in case mail me back at
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