Sticking throttle

[C420sailor]

Dudes,

Had this issue on my 98 SOHC. Throttle plate would stick closed, making power application jerky, to say the least. Cleaned the TB, problem went away. Cool.

My 99 5.0 is doing the same thing. Took the TB off, cleaned the hell out of it, but it’s still sticking. I can feel it with the throttle body in my hand, so it isn’t a cable/cruise issue. If I close the throttle very very gently, it isn’t bad, but at a normal or rapid rate? It sticks pretty hard. It is affecting drivability to the point that it’s kinda dangerous, and I won’t let anyone else drive the truck.

Any suggestions? Wondering if I need to pull the throttle plate out and polish the bore…or if there is a lube I can apply that will last. Worst case I guess I can replace the TB…

 

[410Fortune]

Never had that before!
Always resolved with a good
Lube and clean
If it’s sticking mechanically then you have to clearance something Clarence
If you need 5.0 tb let me know

 

[C420sailor]

What are you using to lube the plate? I’d imagine it has to be something that’s not oil/hydrocarbon based, or the gasoline vapors will solvate it quite rapidly. I was thinking maybe a very light coat of silicone grease.

 

[C420sailor]

Pulled the TB again. It was a little dirty. Took acetone and a toothbrush to it, got it squeaky clean. It was still hanging up with some axial pressure on the shaft—like the side of the plate was hanging up in the bore with the throttle closed. I threw some abrasive in there, worked the plate a lot, then polished that part of the bore. Loosened the screws and adjusted the plate in relation to the shaft. Much smoother now. I’ll see how it is when the truck is hot—seems to be worse then.

 

[donalds]

Ball bearings inside must be shot
lead to leakage around the shaft vacuum leak

 

[Metalface]

I can second that I've dealt with ****ted our bearings that let the plate rotate. That's something to consider. If they're sealed (I really don't remember at this point -- one of the first things I tackled when I first got the truck) I'd say pull the seal lube em up and close em up.

 

[C420sailor]

It’s much much better now—I’ll see how long it lasts. If it comes back, I’ll do the bearings

 

[fast_dave]

Just sayin'

If I remember correctly, my '98 OHV throttle body had a yellow sticker on it, advising that it was teflon coated so as to help prevent the butterfly getting stuck.

The teflon coating may be gone due to age/wear & tear/numerous cleanings -

Also, the 2 axle holes in the aluminum throttle body that the butterfly shaft passes through may be oblong (as opposed to perfectly round) due to age/wear & tear/flooring it...

 

[C420sailor]

Yeah, that coating only lasts so long. I had never cleaned the one on my SOHC and I think it started to hang up around 150k? I remember the sticker, but I could not get the sucker clean without heavy duty solvents and scrubbing. Oh well.

It seems to be doing well now. The holes in the plate appear to be large to allow for adjustment.