My honda idles funny...up and down repeatedly...anyone help?

Question

My honda idles funny...up and down repeatedly...anyone help?

Answer 1

As HONDA GUY says you likely have a Idle air control valve that is dirty or bad.Also one easy check to make is to make sure the coolant level is good.If your coolant is low(due to poss. leak)the IAC valve which operates one of its parameters off coolant temp can search up and down for idle when it doesnt see a hot or cold reading!If coolant is good try cleaning the IAC valve before replacing it.

Answer 2

Honda Guy I agree with you on #3 There is a vacuum leak or the E.G.R is stuck open on this Engine. My advice apply vacuum to E.G.R. if nothing changes then the EGR is faulty if the engine stalls then there is a vacuum leak some where else. Good luck  

Answer 3

I had this symptom on my Honda it could be called a "rolling idle".  My problem was a faulty thermostat. It got replaced and the problem was gone. Not too costly.

Answer 4

The condition is called "hunting for an idle".  it happens when the idle is not controlled by the idle air control valve.  There are three possible reasons for that to happen.

1) the idle air control valve is electrically "dead".  the idle air control valve is located on the side or under the throttle body and it has a plunger that extends into a port to vary the amount of air that bypasses the throttle plates to maintain the idle.  If the valve is electrically burnt out the plunger can't work and the result is you are hunting for an idle.  if the IAC valve is toast you have to replace it

2) the passages that the air flows through that are controlled by the idle air control valve are clogged with carbon.  Think of 'soot in a chimney' and you'll get the idea.  over time carbon builds up in the passage that the air that bypasses the throttle plates flows through.  when that happens the plunger that is moving in and out to control the idle air volume has no effect.  you can clean out these passages by removing the valve and using a carburetor cleaner or throttle body cleaner to dissolve the build up

3) there is vacuum leak after the throttle plates.  A large vacuum leak will cause the unmetered air to enter the engine and the IAC will not be able to regulate the idle.  

these items are in order of their probility with #1 and #2 being about equal in probability.  #3 is least likely.

hope that helps

Answer 5

have u tried resetting your computer? disconnect the negative battery cable for 10 - 20 minutes. reconnect it and restart the car. leave it idleing for ten minutes. then turn the car off and then restart it and see if it has done anything. if not, then i have no idea.  

Answer 6

its probably your TPS throttle positioning sensor. My car did this it would go from 800 to 1500 rpms repediatly sometimes higher. It was hard to find the tps but that fixed it