Anonymous asked in Cars & TransportationCar MakesHonda · 1 decade ago

rpm of my honda accord goes up and down when in park or neutral why?

6 Answers

  • Anonymous
    1 decade ago
    Favorite Answer

    You din't mention what year / model. If it's more'n 8 or 10 years old I'd look for dried and leaking vaccuum lines.

  • Anonymous
    1 decade ago

    This is a common problem with Hondas and many other cars.

    The sources of the problem vary, but they are all related to the air intake system and simple to fix.

    1. The idle air control value (IACV) is stuck open or closed. Clean it (inside and out) with brake cleaner. If it still has a problem, replace it or bypass the water hose it uses to warm up the throttle body. This is an easy job to do on the street, but give yourself about 2 hours for any work you do on it AND have access to your ratchet set, screwdrivers, and possibly have a few new/small hose clamps on stand-by, in case one is busted or badly deteriorated.

    An IACV bypass should only be done if you live in a warm climate. Essentially, you re-route the water hose that comes from the motor and to the IACV. The re-route is routing the water from the motor back into the motor. Then you re-route the hose output/input on the IACV back to itself. Again, only do this in a warm climate.

    If you do this and the problem is still there, the ECU has discovered that the tempurature outside is too cold and you need to replace the valve.

    2. The air/water return hose on the idle air control valve is busted open. simple... replace the hose/hose clamp. Then bubble/bleed your radiator.

    3. The gasket between the air idle control valve and the throttle body is worn out. Replace the gasket if you can get it as a stand alone item.

    4. The throttle body valve is extremely gunked up. This is usually an indication that the throttle body valve is sticking, but likely telling you that the IACV is stuck. The IACV sticks for two reasons... Carbon build-up and rust from radiator water corroding the valve.

    90% of these problems can be addressed by cleaning the parts...Until the IACV eventually corrodes too much or the gasket wears out. Pull the components out of the car, place them on a rag and spray the hell out of them with brake cleaner until all carbon deposits are gone. This means unbolting the throttle body from the intake manifold and unbolting the IACV from the throttle body. It will require some prep work, like taking off the air intake system and associated hoses. If you haven't done that before, I suggest you label the hoses you remove.

    Source(s): I've done this 2 times on 2 different Honda's I've owned.
  • 1 decade ago

    If this is a small change in RPM, I think this is normal. I've noticed a slight jump in RPM on my Grand Prix when I shift to neutral or park. My guess is that the engine has less of a load on it because it's disengaged from transmission, and therefore can run faster.

  • 1 decade ago

    AHA! Finally a question I can answer. I had this same problem when I bought my 92 Accord.

    If you mean your car idles high then drops suddenly, and repeats, follow this manual.

    What you want to do is find the FITV valve. It on the right side of the intake manifold. You do not need to remove it. This is just a reference pic.

    Then take the top off by removing the 2 screws. The image show the entire FITV removed from the engine but you do not need to remove it.

    Then all you do is tighten the white screw inside, wet the gasket with grease and close it up!

    All in all it should take under 5 minutes and is guaranteed the easiest fix before going to your IACV.

    Source(s): Personal experience and all around love for Hondas
  • How do you think about the answers? You can sign in to vote the answer.
  • 1 decade ago

    Rough idle? Can we get the year and mileage on the vehicle? Rough idle happens on older cars that are usually poorly maintained.

  • Anonymous
    1 decade ago

    Well you didn't say what Year so im guessing its a old car.

    The RPM gauge is broken and it needs replacing.

    Source(s): 10 years of a Mechanic Own Serval different cars and happen to be a Honda Accord
Still have questions? Get your answers by asking now.