Nissan Micra K12 Throttle Body Removal and Clean
Welcome to this guide on how to remove and clean the throttle body on a Nissan Micra K12.
This procedure was done on a 1.2 2003 petrol model.
As I couldn't find a good tutorial on this process I thought I would have a go myself and then put together this guide for other people.
The process is actually relatively straight forward once you know how.
I was experiencing juddering at certain points on the rev range and when the car was in a certain gear, MPG had decreased plus some hunting when the car was idle. So I decided that I would clean the throttle body to see if that would help.
I actually didn't know exactly where the throttle body was located on this model. It's actually located under the air intake box/top manifolds which are shown below. It's actually located inside and under the top of the plastic manifold housing. Once you have removed the throttle body you will realise that it's actually connected to one of the electrical connections on the top of the housing that you will need to disconnect as part of this process.
Throttle body location
This is where the throttle body is location on a 2003 1.2 petrol Nissan Micra K12.
This is a list of tools and other items required to get to the throttle body, remove it from the housing and then clean it:
Pliers or grips
10 mm socket
Toothbrush or cotton buds and an old but clean cloth
A good carb/throttle body cleaner
So here are the steps.
Step 1 - Remove the air intake and air filter box
Remove the air intake pipe (highlighted by the red arrow) by removing the plastic lugs that hold it to the front of the engine bay and then remove the other end from the air filter housing on the right. I had to slightly twist mine and then gave it a hard pull to detach it.
Then remove the air filter housing from the manifold housing. Do this by unclipping the metal retaining clips (highlighted in blue in the image below) located on the front and the right side of the housing. There are only two clips that hold this in place. They simply unclip upwards and one remains connected to the top housing and the other remains connected to the air filter box.
Once you have unclipped the air filter housing the front of it may drop away from you. It should not fall off completely as the back is held in place by the box being slid into holders in the back of the top housing. To remove the air filter box simply push the front down and when it's at a certain point pull the air filter housing towards you. This will pull it out of the rear mounts. Try to look at the rears mounts when you do this so that you can be sure you pushed it down enough to be able to pull it forward without snapping the plastic mounts on the back of the top housing.
You should see this when the air filter housing has been dropped away from the top housing. The air filter itself may have stuck to the underside of the top housing like mine did so just pull it off and place to one side. I would suggest replacing it with a new filter whilst you are doing this as you will have to put it back in when you reassemble.
Now just slide the air filter housing out of the engine bay so that you can continue. You will see this.
Step 2 - Disconnect Electrical Connectors
Disconnect the three electrical connectors as highlighted in red.
The one to the left of the top housing is the actual throttle body connector.
Once the one in the middle of the top housing is unplugged, make sure you gentle pull it out of the recess that the rest of the cable lies within and gently push it to one side out of the way.
Do not just pull these connectors as they are made from plastic and will snap. They all have a small tab which needs to be depressed at the same time as gently pulling them. Do not pull them too hard as they do not need it. They will disconnect very easily if the tab is pressed whilst pulling them.
Step 3 - Disconnect Breather Pipes/Hoses
Disconnect the two breather hoses/pipes as highlighted in red. You will need to use a pair of pliers to release the retaining clips that hold the end of the pipes tightly sealed in place.
Just squeeze the release arms on the retaining clips with the pliers and slide the retaining clips along the pipes until they are free of the housing connector.
Now just gentle pull the hoses/pipes off the housing connectors. Again, you do not need to pull these hard. They should just slide off with a light pressure. Remove the centre hose from the recess in the top housing and push it out of the way.
You should now see something like the image below. All electrical connectors have been disconnected and the hoses disconnected. I took this picture before I had moved the centre hose out of the way so you shouldn't have this in place at this stage.
Next remove the breather hose mount, shown below, from the top housing. If you don't remove this you will not be able to remove the top housing completely if you leave the rear hose attached. Alternatively, you could leave it bolted on and just remove the other hose from it and then remove the top housing with the mount attached. I just unbolted it and pushed it out of the way so I didn't damage it.
Once you've removed the mount then it should look like the image below. Just move it gently out of the way so that it doesn't interfere when you remove the top housing.
Step 4 - Remove Top Housing
You can now remove the top housing by simply removing the bolts highlighted in red in the below images. They are all 10 mm.
Remove the three front bolts.
Remove the two bolts on the left rear of the housing.
Remove the two bolts on the right rear of the housing.
Once the seven bolts have been removed you can simply pull the top of the housing up towards you and it should separate from the bottom section of the housing.
Warning: Do not pull this top section up too hard. You should be able to just pull it up with a little force. The top section is attached to plastic manifold inlet pipes toward the rear and they are pretty much held on by O rings. Try to pull the top section of the housing up towards you in a straight motion. Try not to bend it as you pull it up. It should come off fairly easily.
Warning: This top section actually contains the throttle body itself so take care. Do not just drop it to one side as you may damage the throttle body that you are about to clean - if you are not replacing the throttle body itself of course.
You should now see the image below once the top section is removed.
Step 5 - Remove Throttle Body From Top Housing
Once you've pulled off the top housing turn it over to see the location of the throttle body.
Simply remove the three bolts that are highlighted in red in the image below. They are 10mm so just use the same socket you used to remove the top housing bolts.
Once you have removed the three bolts you can now remove the whole throttle body. The throttle body is now only held in by the top of the electrical connector on the outside of the top housing.
It's a bit tight so just pull the throttle body towards you whilst wiggling it slightly as the rubber seal is a little tight. Don't put too much force as you might snap the plastic top housing.
You should now see the housing like this once the throttle body has been removed.
Step 6 - Clean The Throttle Body
To clean the throttle body I used a small headed toothbrush, some clean rag and a good carb / throttle body cleaner.
Warning: Carefully follow the instructions on the carb cleaner. Do this work in a well ventilated area, preferably outside and wear a suitable breathing mask. Take extreme care not to inhale the fumes from this cleaner or the dirt that it removes from the throttle body.
I used the following carb cleaner which is available from a well known parts store for about £8.
This was the state of my throttle body when I got it out. It was really clogged up and clearly sticking.
Simply attach the small pipe to the can of carb cleaner and then spray into and around the inside of the intake of the throttle body and all over the butterfly valve.
Then just brush the whole of the inside of the intake (front and back) and butterfly valve with the toothbrush and/or rag.
The dirt should come off quite easily as the carb cleaner is really effective. Keep doing this until the intake and butterfly valve are as clean as you can get them. Keep wiping off any residue with a good clean rag as well as you do this.
After about 10 minutes of cleaning I had a nice clean throttle body as shown below. Yours should look pretty similar when complete.
Step 7 - Refit Your Throttle Body And Reassemble Other Parts
Warning: Before refitting your cleaned throttle body you should ensure that the throttle body is dry and does not contain any residue from the cleaning agent.
I left my throttle body to completely dry for about an hour or so just to be extra cautious before proceeding with refitting.
Refitting your throttle body and reassembly is just really this guide in reverse from step 5 back to step 1.
Warning: Take care when reattaching the top of the housing to the bottom and the intake pipes as they have O rings present. Ensure that they are correctly aligned before pushing the top housing down into place. Be careful not to pinch or tear the O rings. If it's tight to refit over the O rings then either replace the O rings or simply apply a small smear of engine oil around the O rings which should help refit the top housing.
Warning: Do not over tighten the bolts that hold the throttle body in place or the top housing.
Warning: Once you have reassembled everything it is a good idea to just double check that all the breather hoses are reattached and secured in place and that all the electrical connectors are attached securely.
You should now be able to start the car and test accordingly. If this process has been successful then you should have a smoother throttle response and possibly more accurate. Mine stopped juddering at certain revs and seemed so much more responsive. I am also now getting much better fuel economy.