For all you 2.0 d-jet folks....

Look at your throttle body plate (the valve that closes over the TB opening).

Does your valve have NO hole in it, one small hole, or does it have a nut and bolt in the hole?

See three samples below. The third photo doesn't show the small hole plugged, but you get the idea. It is like the second with a nut and bolt plugging up the hole.

Bonus question:

What purpose does the hole serve and why is it closed on some TB's?



Thanks,

Len


PHOTO 1 NO HOLE:
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PHOTO 2 SMALL HOLE:
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PHOTO 3 HOLE PLUGGED - THIS PHOTO DOESN'T SHOW IT, BUT JUST IMAGINE THE HOLE IN PHOTO 2 IS PLUGGED WITH A SMALL BOLT AND NUT.
Click to view attachment

Idle bypass circuit plugged with carbon so someone drilled the plate to get enough air to idle? (unlikely though. you don't get any carbon build up this far up the intake runner.)

It used to be a common modification on muscle cars with carburetors and big cams. To get enough air to idle you had to open the throttle plate too far and it started to engage the transition circuit in the carburetor, or you could drill a small hole in the throttle plate to get enough air through and not have to open the plate so far. Made them run much better and allowed the carburetor circuits to work that way they were intended. Why someone would do it on a FI car though ???

Are you saying that the valve plate is typically NOT drilled on 2.0 d-jet?

OK

Someone must know what the answer is as to why some valves have a hole and some do not.

I found this photo of a bunch of TB's in a old post. They apparently came from a shop that would replace FI with carbs and had these throttle bodies as scrap.

Note some of them have a hole in the valve plate and some do not.

I'm puzzled as to why that is. I don't think those with the holes were drilled, they look like they came that way.

Anyone?

Click to view attachment

They came both ways. I asked the same question a few years back.

I just happen to have a recent picture of mine. You can even read the part number.

This is from a '73.

Click to view attachment

Did you ever get an answer?

They came both ways, but we don't know why. Interesting. Theories?

1) I know my car was a CA car - but I don't know if that's the original TB or not. Could it have something to do with the car having additional emissions requirements?

2) My car also had A/C.... but that was dealer / owner installed, so it is doubtful that has much to do with it. I was thinking the compressor added some additional load on the motor (especially when engaged) and perhaps they needed the additional idle so it wouldn't stall. That makes little to no sense though.

I have nothing else. It would be nice to know though. They didn't come that way for no reason.

Do you know what state your car is from? Do you have any idle issues?

Mine was also a California car originally, before it was introduced to rust in the Mid-Atlantic.

edit: I answered the origin question before you asked it, and then missed the second part. There weren't any idle issues except those caused by a clogged fuel filter. Now there is a lot more that has to be done before we are back on the road. (fuel lines, intake studs, complete tune up, ??)

Hole could be placed on some of the TBs to reduce the chance of vacuum lock. In this condition there is an extreme amount of vacuum pressure on the backside of the plate, and a large pressure difference from that of the front side. When this happens, the throttle blade tends to want to stay in the closed position, due in large part to the intense vacuum pressure created by the engine.

Can be adjusted out with idle bypass, or even tipping the plate a small amount. Or drilling a small hole in the plate.

BTW, all my 73-74 2.0L had the hole, a 76 I owned did not.

Interesting topic. The TB on my '74 2.0 CA car came with a hole. I just installed a rebuilt TB that I bought from a member that has no hole. It was rebuilt by Van Cafe. During the process the intake was re-sealed and all vacuum leaks were eliminated.
Now the car is very hard to start. It feels like a carbureted car with no choke.
Before I start working through it I'm planning to contact Van Cafe and ask about the hole. I may also try re-installing my old TB.
Jack