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Howdy folks. I did a repair on the Pup today and thought since this is common problem with all makes and models that I'd share it with you guys on the forum.

If you are experiencing idle issue problems related to vacuum (I don't like this word, but that's another story) make sure to check the condition of the throttle plate/body assembly. In other words, the actual throttle, and in particular the shaft.

Many times (VERY typical with early Toyota FI) the steel shaft will make the aluminum housing or bushings out of round, causing a vacuum leak right were the shaft enters the body. This is a common failure of high mileage motors. Just check the throttle plate by giving it a little shake side to side and in and out. There should be VERY little play here. This is easy to find on a smoke machine if you have access to one (one of my favorite tools). In any case, just something to add to the memory banks if you are trying to hunt down a leak. (Another nice one is finding the vacuum leak from your brake booster.)

In my particular case, the Pup has a carb. I was able to find a Chevy Luv in the junk yard that had the same throttle plate, and simply replaced the throttle plate since the carb was working fine otherwise. In fact this throttle plate is better because it has an actual mixture screw without having to drill out the safety cap.

P.S the factory settings on the mixture screws with the safety cap shouldn't be played around with unless you have access to a gas analyser that will give you an air fuel ratio reading. Otherwise, you will be very hard pressed to reach the 14.7:1 ratio. If you did mess around with this, a standard rule of thumb is 2 turns off the seat, more if the engine is knocking, less if you smell gas and have poor fuel mileage.

-Kevin
 
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