Q: Changed/removed the thermostat, now idles up and down over and over... 1994 Honda Accord

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I have a 1994 Honda Accord I took out the thermostat and I checked all the hoses when I put everything back together and Crank up the car and let it run for a while then I noticed the RPMs is going back and forth Rebbing up and down so I took off the radiator cap and I looked in the coolant was running out I check the hoses there was no pressure on the Hose but the car just kept Rebbing up and down so I cut the car off

My car has 125497 miles.
My car has an automatic transmission.

Hello - if I understand correctly, you may have completely removed the thermostat, rather than replaced it? If so, the engine will warm up more slowly, and that will confuse the engine management computer, and cause the engine to run with a richer fuel mixture. The oxygen sensor will try to compensate for this by commanding the fuel injection to use a leaner mixture, and a continuing cycle will follow. It is also possible that you bumped a vacuum line or electrical connection for the idle air controller and that component is not operating properly - causing an eratic idle. I recommend a rough engine idle inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.

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