Rep: 13
1
1
Engine surges, up and down, when cold, from about 1,000 rpm to 2,000 rpm.
Possibly related, when using cruise control, engine gradually speeds up to about 75 MPH, then drops back to set speed, then speeds up again. Tapping the 'lower speed' button slows it down, but it starts climbing again.
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Rep: 10.9k
12
10
18
Sounds as though you have a vacuum leak. Try looking online for a vacuum line diagram.
With the engine running and in park, grab a can of brake cleaner or carb cleaner and spray all of the vacuum lines and listen for a change in idle. Replace as necessary.
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I would not recommend the carb cleaner. Try listening with a hose close to your ear and the other end sweeping around the intake. The unknown age of your plug wires with carb cleaner is dangerous.
Kevin
Rep: 157
3
Most of the time it is caused by low coolant. The idle air control motor has a wax element that is heated by the coolant.
Another possible cause is a vacuum leak. Hondas have a deceleration fuel cut off. This is how it works...
When the rpm's are above 1500 with the throttle plate closed it kills the fuel injectors to conserve fuel. This is why it surges. Engine rpm's go up, throttle plate is closed, kills injectors, rpm's drop, and fuel returns. Repeat.
Hope this helps.
Kevin
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Rep: 91
3
There also sensors that regulate the idle or speed. I would check that.
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low coolant, had the exact same problem with mine when a coolant line decided to blow, engine was drained of coolant, when i started it it idles normally for maybe 1-2 minutes, then would go surging from 1000-2000 rpm, filled her up with coolant again, problem solved for me
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