Throttle Body Cleaning

Civic 2001-2005 - D16V1

  1. Nighthawk
    Difficulty Level:
    This car has had a slightly sticky throttle ever since I bought her for the missus, not to the point where it is dangerous, but to the point where it meant that you could not accelerate smoothly as it would lurch forwards or do nothing at all. You would put pressure on the pedal, and there would be nothing until the foot pressure overcame the stick and then it would suddenly rev up and lurch forwards. I could get it to behave but the missus was completely lost by it.

    A few attempts without ripping the throttle body off took place. Firstly, the throttle cable was a bit sticky, so this was soaked and the throttle body spindle was sprayed with lubricant. Made a difference for a week or so, then started up again. So, got some carb/throttle body cleaner and sprayed some within the air intake and directly onto the throttle body butterfly valve. This helped a lot actually, but it was still there although not as bad.

    So, today, I decided to take it off and give it a proper clean. The result? She now has no hesitation or stickiness anywhere at all. She pulls off smoothly (except for the clutch but thats a different story) and no longer lurches when suddenly taking the foot off the accelerator and allowing her to slow down naturally.

    This is a pretty simple job, just be aware that you will be dealing with radiator coolant, so make sure the car is COLD!

    - 10mm socket with extensions and spanner
    - 8mm socket and/or a decent size phillips screwdriver
    - Throttle body cleaner
    - Plastic bag
    - Q tips and/or cloth
    - Pliers - either snub or long nosed
    - Cardboard box (or something you don't mind getting grease and muck all over)
    - Eye protection
    - Common sense and patience

    Depends on how clean you want it, took me around 2 hours or so as I wanted it as clean as possible, but if you don't care, then you could get it done much quicker, say within an hour.

    STEP 1:
    First step is to disconnect the battery. You will be uplugging numerous sensors so rather disconnect the battery to prevent the car flagging up error codes when you turn her back on.

    (The piece of rubber I put there to prevent the cable from popping back and connecting to the terminals again)

    STEP 2:

    Remove the air box. You can open up and remove the filter if you want, it does give you a bit more room to remove the air box, but its not essential - your call.

    The air box is held on by three 10mm bolts as circled in red on the first picture, and an 8mm bolt holding the securing clip onto the throttle body as shown in red on the second picture. don't forget to remove the hose as circled in blue as well.



    Disconnect the IAT sensor


    Pull the air box straight up to break the seal of the gasket around the top of the throttle body which you loosened with the 8mm spanner and once this has popped loose, slide the air box to the right and up and it will disconnect from the resonator box.

    STEP 3:

    With the airbox removed, you will see this. You need to disconnect the following sensors as circled:

    - EVAP purge valve
    - Throttle position sensor
    - Idle air control valve


    You need to disconnect the throttle cable as well. Anyone who remembers how you used to disconnect bicycle brake cables from handle bars will have no problem with this, its exactly the same design. Move the throttle body spindle by hand so the cable has slacked, and then simply remove the cable by pulling it out of its seat.


    STEP 4:
    The IAC is cooled using radiator coolant so these pipes need to be removed so make sure the car is cold when you do this. Simply remove the two clips and pull the pipes clear. There will be some fluid loss, but not alot. You will now introduce air into the cooling system, so be prepared to bleed it out a bit if necessary (mine wasnt).


    STEP 5:
    With everything now disconnected, its time to unbolt the throttle body itself. This is held into place by 3 bolts and one nut. Not sure why they designed it that way and didnt just use four bolts, but anyway. They are all 10mm's and shown here.


    Remove them and gently break the bond and pull it straight up. There is a seal underneath the throttle body, Honda recommend changing it, mine was still pliable and undamaged so I left it.


    Shove a plastic bag there to prevent any foreign bodies finding their way in.


    STEP 6:
    At this point, the boss came outside with a cup of tea so I decided to have a closer look at the throttle body now it was off the car. The one side seems cleaner than the other, this is because I had already sprayed throttle cleaner in a few weeks beforehand as mentioned at the start of this. I had also sprayed some of the spindle as well which is why it is partly cleanish.... it was absolutely caked.

    The top of the throttle body looked like this (remember, already been kind of cleaned beforehand):


    The base of the throttle body (untouched) looked like this. This was what the top of the butterfly valve looked like before I had cleaned it.



    The throttle body spindle where I had not managed to clean before, looked like this:


    The spindle was gritty to turn by hand, you could feel it binding ever so lightly, but it was enough to cause an issue.

    STEP 7:
    Get some eye protection on, throttle cleaner is nasty stuff if it gets in your eyes and it will spray everywhere. Put the body inside a cardboard box to try to contain the mess and set to work. Spray within the body, let it settle, and use Q tips to help remove the built up carbon deposits, manipulate the butterfly valve by hand, spray more, more Q tips and cloth etc, keep cleaning until you have removed as much as possible. Spray the spindle, get as much junk off there as possible, a decent bottle of throttle cleaner with a concentrated high pressure nozzle works really well here. Spray everything and get cleaning. Once that is clean, I removed the Idle Air Control Valve. This is held on by 3 screws and a gasket. Remove the screws, the IAC valve and the gasket and get to cleaning this too.



    STEP 8:

    Once you have cleaned everything as much as you can, reinstall everything back in the reverse order, make sure the spindle is moving smoothly and ensure that you connect all the sensors back. The back of the throttle body looks like this now:


    There is staining of the valve, but other than that, it is clean of any junk on it.
    Duc de Pommfrit likes this.

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  1. legend-ary
    great guide. that is something I am planning to do on my Jazz very soon.
  2. Ichiban
    Nice one fella.
  3. SpeedyGee
    Great guide and a job well done @nighthawk
  4. Anonymous
    Excellent guide. A job that really needed doing.
  5. RogerH69
    Great guide!! Detailed, with lots of pictures.