What is this part?

I have a 91 gmc with 305 auto. What is the second set of linkage on the driver's side of the TBI in front of the acc/Tv cables? It has an arm coming out the side, a large hose coming out the top, and a vacuum hose running to the base of the TBI unit on the passenger side. Right now it's not hooked up, but when I move the arm, the RPMs seem to change slightly. What is this thing?

I have a 90 GMC with a 350/Auto. On the drivers side of the TBI (from Top to Bottom) is the Throttle Cable, Cruise Control and TV Cable.

So I think you are refering to the Cruise Control.

//2000CAYukon

It's actually about 2 inches in front of the cables on the corner, separate from the others. It's attached to some kind of spacer plate under the TBI, not the TBI itself. The truck doesn't have cruise control (now) but from what I've fixed so far anything's possible.

I don't have my truck with me today or I would go out and look at it. I also have the factory service manuals for 1990 at home. I can take a look later tonight and post what I find.

//2000CAYukon

Thanks, I appreciate it.

Well I took a look at my 90 and I have nothing on the drivers side of the TBI as you describe. The service manuals also show nothing.

Could be a dealer installed item or an aftermarket item. GM part numbers will be 8 digits long (usually) so look for any part numbers on it.

Some aftermarket cruise control devices do require vacuum to operate. That would be my guess.

//2000CAYukon

Thanks. It looks like it may have been connected to the throttle linkiage at one point. there are corresponding marks on each linkage. The 1" hose coming out of the top is confusing me. There is a vac line running to the passenger side of the TBI going into the unit by the IAC. The mystery part is also connected to some kind of spacer plate under the TBI. The truck doesn't have cruise. Could this have been a swap from something else? Both vac hose (the big and the little one) are plugged. rehooking the little one seems to have no effect other than idle speed.

The intakes on the TBI trucks were the same 87-95 so it is possible that it was swapped out from something else (like a Tahoe/Suburban).

Did you find any part numbers? Can you post a picture of it?

//2000CAYukon

Here is a picture of it. It's the big ass hose connected to it on the bottom right of the TBI unit. It's probably something really simple, but I'm no mechanic. I'm just trying to clean up under the hood. The guy had wires running everywhere, pieces held on with mechanic's wire.... But hey I only paid $1000 for it and it runs great with a straight, rust free body.


http://files.automotiveforums.com/gallery/showphoto.php?photo=31661&password=&sort=1&cat=500&page=1

I don't know what that is. There is nothing like that on my 90. My guess is that the TBI unit is off another year/model. There is an 8 digit number on the TBI unit that will help figure that out.

Plug any open lines to keep dirt out.

//2000CAYukon

Looks like a throttle body heater to me. Some vehicles use heated coolant to heat the t.b. That large hose looks like a coolant hose. If it's not hooked up it's not doing anything. You may be able to remove it if you can find (or make) a cover plate for the opening.

So is it better to remove the spacer it's on completely or just block off the plate?