I recently had my throttle body shaft seals replaced by a reputable guy on another forum. When I got the tb back the throttle plate was very difficult to open. After opening and closing it by hand for about half an hour it had gotten better but it still didn't slam shut like it should. I put it on the car and heat cycled it a few times (idling of course) to see if it would break in but it didn't. When I free rev the car and it gets stuck at about 3k rpm and then gradually falls back to idle. My TPS is set correctly with ECMLink and I don't have any boost leaks.

The guy who rebuilt it said it probably just needs more breakin time and heat cycles. I wanted to check with you guys to see if this sounds normal. I've personally never heard of breaking in throttle body shaft seals, but maybe that's a thing?

Nope, not a thing at all. If it doesn't open/close correctly, it wasn't rebuilt properly. If it's tough to open, my guess is the plate isn't perfectly centered and is binding up on the bore of the throttle body. Not sure if the seals will still be in good condition if there was a lot of friction upon open and close, or if the shaft screws are still fine if they didn't pass through a perfectly positioned plate.

I'd suggest taking it back apart and examining it. Then assess any damage and put back together properly.

The two nuts on either side of the throttle plate shaft may be on too tight. I had this problem one time after I replaced the shaft seals, and the gas pedal was very "sticky."

You should never have to take off the one under the TPS sensor. I don't think I've ever tightened down the one under the springs so tight that it would cause this, but I do it all by hand (no power tools), so it might be possible.

I bet the springs aren't wound around the 3 times that they need to be and are only wound around the shaft two revolutions. I had that exact thing happen when I rebuilt one and didn't turn the springs the 3 revolutions that it needs.

Detective Coating said:

I bet the springs aren't wound around the 3 times that they need to be and are only wound around the shaft two revolutions. I had that exact thing happen when I rebuilt one and didn't turn the springs the 3 revolutions that it needs.

Click to expand...

It's two revolutions, not three. Three will make the spring coils bump out and cave in a bit (instead of being in line with each other), or start to overlap themselves I believe.

It's harder to open and slower to close than it was before the rebuild so I don't think it's the spring tension. I talked to the vendor again and he offered to fix it and pay for shipping both ways if I can't find out what's wrong with it. He seems like a stand up guy so I don't want this problem to reflect bad on him, so thank you to whoever deleted that one post.

When I inspected the TB it looked like the throttle blade was positioned correctly and didn't seem to be binding or rubbing against the TB, but I'll look again just to make sure.

Are different seals used for NT throttle bodies than normal turbo throttle bodies? He said he double checked to make sure the seal wasn't pinched, I'm just wondering if maybe the turbo seals are a little too large and are creating some extra friction around the NT throttle shaft.

Technically, yes, the N/T seals are shorter (2mm vs. 3mm tall) than the turbo seals. But I've always used turbo seals without any issues.

snowborder714 said:

It's two revolutions, not three. Three will make the spring coils bump out and cave in a bit (instead of being in line with each other), or start to overlap themselves I believe.

Click to expand...

Thanks for correcting that, been a while since I've done one but knew the one time I had either over or underdone the coil and it made it super slow to close and wouldn't fully close without some force on the plate.

I took the TB off and loosened the nut under the TPS and now the throttle blade snaps shut like it should. I had to loosen the nut about 1.5 revolutions before it felt right. I guess the slightly taller turbo shaft seals pushed against the nut enough to cause the problem. The throttle works as it should and holds 30psi in a BLT so I'm all set.

Odd solution, but glad to hear it's working!

The spring problem can be solved by marking the spring with a paint marker prior to disassembly.... if the wound up spring doesn't line the paint back up that goes across it's coils then it's not wound properly.

Glad you got it figured out.

I had a sticking problem after rebuilding a NT throttle body with turbo seals. I think I ended up smashing the seals in tighter because I was worried about having problems down the road if I left the nuts loose. That TB is still on a shelf, but I plan to put it on my Colt someday.