How to rebuild your throttle bodies

Transcription

1 It has been requested of me to post this procedure and I am more than happy to do so. Just got all the pics sorted out so here we go. This discussion will be using the B10 BiTurbo and E32/E31 throttle bodies as the example but the principle is the same for other cars of this vintage. Remove your throttle body from the car. The E34 cars are easy, the e32/e31 cars are a bit more of a PITA. For the E32/E31 Undo the clips on the air box and loosen the ring clamp at the point where the ducting attaches to the throttle body. Undo the MAF plug and the PCV hose from the duct boot (I think that is what the hose is). Then remove that entire assembly on both sides. Best to use a 1/4" drive socket, a 10mm head and a 3" extension. The toughest bolt to get out is the one that is underneath, closest to the engine. The best way to get this guy out is to lead the socket head in on the extension only until you can seat it by feel. Then attach the driver and remove the bolt and then the other three. Once off, disconnect the vacuum hoses and the hose to the fuel pressure regulator. Finally, twist off the electrical connector NOTE the vacuum lines can be very stiff and brittle. As a precaution, buy some vacuum tubing in both diameters (sorry I am unsure of what they are) and get some plastic T connectors as well that will fit the larger lines ahead of time. It is common to break the tubing and sometimes the vacuum Ts as well. I would also suggest picking up new gaskets for the throttle bodies as well (part # ). The ones on the car often are oil laden and sometimes come off in pieces. For the E34 Disconnect the hose from the throttle body and where it attaches down towards the front of the engine and remove it gives more working room. Disconnect both electrical connectors from the throttle body and then undo the 10mm NUTS. The difference here on the E34 is it is just nuts that hold the throttle body on, so be careful when undoing them (will be a fun hunt if you drop them). 1

2 Once out, your throttle bodies will look like this (BiTurbo on top, E32/E31 on bottom). 2

3 On the BiTurbo throttle body, in looking at the picture, you will also want to undo the 2 10mm bolts that connect the electrical connector that is on the LHS in the photo. My suggestion is to undo the bolts that connect the entire housing to the frame of the throttle body (silver bolts holding on a silver u shaped bracket that holds the electrical connector). The other bolts attach the electrical connector to the mount but I noticed that they are bolted in a slot, so it is probably best not to mess with that. Once undone, slide the entire assembly off the shaft from the throttle body and you are good to go on the next step. 3

4 Next you will want to undo all the screws/bolts that attach the black cap to the throttle body only (don't touch any others). I am using an E32/E31 throttle body for this example, but it is identical to the BiTurbo. There should be about 7 bolts/screws. On my BiTurbo, they were all Philips heads. On this E31 throttle body, they are all one way screws (quite common). Make sure you have a good set of vise grips and a lot of patience these can be a bugger to get off. If the vise grips are failing you, get a Dremel and a cutting wheel and notch in a slot in the screw so you can use a flat headed screw driver to undo it. Be careful to not notch the groove too deep as you can cut through the head and then you have to cut the whole head off (don't ask how I know this). Once all the screws are removed, pull off the rubber gasket that is around the electrical connector and then you will likely need to use a flat head screw driver to pry the black cap from the main throttle body. It is magnetic in there so you will have to give it a good tug. Once all apart you should have the following bits and pieces. Clockwise from the top left: Cap; bracket that goes around the electrical connector on the throttle body; commutator; exposed innards of the throttle body. 4

5 Now comes the cleaning part. One reason throttle bodies fail is that the little brushes get stuck because of sludge buildup. As good fortune would have it (for the sake of this tutorial), the one brush on this throttle body was stuck. So, without both working to send a signal, it is bound to cause issues (which this one did). Here's a pic notice how one brush is near the hole and the other one is not 5

6 Here's a pic of the next tools needed. WD 40; Q tips; paper towel; drill; sand paper (about 1200 grit is good); white lithium grease and a jewelers screw driver set. 6

7 The other reason the throttle body cannot function properly is because of gunk buildup on the commutator. Here is a shot of what this one looked like pretty messy. 7

8 So, first thing first. If your commutator has gunk built up on the surface, get some WD 40 on a paper towel and clean off the major gunk. Once you have that done, break open the jewelers set and pry off the brass cap on the bottom of the commutator. There will be a paper gasket behind it, don't lose that. 8

9 Next you want to take a fine jewelers screwdriver and clean out the grooves all the way around the commutator. 9

10 Once that is done, load the commutator in the drill and wrap the sand paper around the commutator and run the drill. You want to make it look like a nice copper color. It doesn't take much so don't sit there and sand it for more than 15 seconds or so. 10

11 When finished it should look something like this. Attach the paper gasket and snap the brass ring back onto the base of the commutator when you are done. 11

12 Now back to the throttle body housing. Arm your Q tips with WD 40 and clean out all the gunk around the brushes. What I do is a pass with a WD 40 soaked Q tip and then a pass with a clean one. Repeat until it is clean. You will also want to take a Q tip and pull some of the fuzz off so that it can fit in the groove where the brushes slide. Repeat the wet Q tip clean Q tip procedure here as well. 12

13 Once that is done, do the lightest squirt of WD 40 in the grooves where the brushes go and make sure they move freely and effortlessly in the groove. If you get the brush stuck at the back edge of the throttle body, just get in behind it with a jewelers screwdriver and push it to the middle. They are spring loaded so it should just pop back. Now we're ready to reassemble. Put some of the lithium grease on the grooved end of the commutator (as shown in the pic below) and a small dab on the very top above the big drum. 13

14 Feed the commutator back into the throttle body. This can be a bit tricky as you need to push the brushes back. If you press them all the way back to where they get 'stuck', you can then drop the commutator right in. After that, get your jewelers screw driver out and pop the brushes back so that they both contact the commutator. Ensure that they are spring loaded against the commutator and not just sitting there (or else the throttle body will not work properly). Now for the cap this can be tricky. Good to have two people for this one or do what I do and hold the throttle body between your knees. You will need to use something like a jewelers screwdriver to hold the commutator down while you feed the black cap back on to the throttle body. The magnetic properties try to pull the commutator out of the throttle body so you need to press this down well. If you feel the commutator pop up on you, stop and check to make sure that it is still properly seated before trying again. 14

15 Once you get the cap back on, I would suggest buying new bolts and screws that have a hex head or Philips head on them so that if you need to do this again it is much easier to get it apart. This is if your throttle bodies had the one way screws. Don't forget to attach the metal clip that goes around the electrical connector and don't forget the rubber gasket that slides down around the electrical connector. Voila you're done. Reinstall your throttle bodies and go for a good drive or do a coast down procedure (for the E32/E31 cars). Any questions, don't hesitate to ask. I have a friend who rebuilds throttle bodies for the E32/E31 for a nominal fee, so if you are not feeling up to the challenge, he can send you a rebuilt set and you just send him your old ones plus the nominal fee. He does not have E34/BiTurbo throttle bodies, nor do I, or else I would offer the same service. Have fun! Rob Original post: 15