Throttle body fun

Yesterday I decided to take the throttle body off my ’86 syncro (2.1 l), to clean it up and double check the throttle valve position switch. Well it turned into one of those “why did I do that?” projects.
I had more than just idle curiosity driving me, the van had been having occasional lag in standing start acceleration which I thought might be due to the throttle valve position switch (TVPS), even though it had been recently adjusted. I was suspicious that the throttle shaft fit in the throttle body was loose and that might be affecting the TVPS.
Getting the throttle body off is pretty easy, I did find that the two bolts holding it onto the plenum were not tight, I wondered if that had allowed a little air leak? Who knows.
Got the throttle onto the bench and gave it a quick cleaning. Wasn’t as oil crusted as I had expected, someone must have been in here in the last few years. The TVPS had a black plastic cover on it, I had not seen that before. It sure keeps the actual switch nice and clean, see photos.
The bore and butterfly had wear in them, as expected. The design of the TB allows axial play and this lets the butterfly rub on the bore. The pics don’t show it quite as well as I had hoped. But there didn’t seem to much if any lateral play that would affect the TVPS setting.
Using a multimeter set on ohms and “beep” for continuity I check the TVPS setting. it was within spec, but I managed to fine adjust it to fall between a 0.003″ feeler gauge and 0.002″ shim stock. I was feeling pretty cocky at that point, and toddled back out the the van to re-install.
It was then I noticed the little clamp that connects the throttle cable to the TB was missing, argh. I must have dropped it between the van and the bench… probably on the gravel driveway. I spent quite a while searching, with magnet too, but no luck.
So I ended up making a quick and dirty substitute. Mild steel and a 5mm hex socket machine screw. It worked out ok.
I figured I’d blow the entire afternoon and take the crankcase breather tower off and check the O-ring that seals it to the case. The O-ring was as hard as hard can be, was it ever soft? It was also broken. The old ring broke into pieces getting it out. I didn’t have a replacement in the collection but I had a spare breather tower and I swiped the O-ring from that.
Cleaned up the oily mess from all the associated hoses, replaced some sections of braided rubber vacuum lines, and put everything back together.
The van runs pretty well the same, maybe a tad higher idle, will deal with that later. Needs a few more miles of driving before I admit it was all a waste of time 🙂
Next move… playing around with AFM spring tension. Yup dangerous grounds.

  1. #1 by Mark on July 8, 2010 - 7:27 pm

    I’m so glad you took pictures of this thing. I was trying to figure out how my throttle valve switch triggered (on my Westy) and I can totally see it now! Maybe I have a bad switch??

    • #2 by albell on July 8, 2010 - 7:58 pm


      maybe you do have a bad switch Mark. I have heard of such, and ones that test ok on bench but fail when in van. It sure is easier to set them on the bench than in car.



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