You didn't indicate in your post if you had checked the TB shaft;
Put a dial indicator on the shaft (with the throttle blade removed), and check the runout of the shaft. It should be less than 0.001" total runout.Is the TB shaft bent or has more than 0.001" run-out?
Check the TB shaft on a surface table to determine straightness (don't eyeball it).
It should roll on the surface table like a bearing.
If it doesn't, replace the shaft. You should determine the cause of the shaft run-out prior to installing a new shaft. Next, Verify the "notch" for the throttle blade is parallel with the axis of the shaft.
You can accomplish this by holding the shaft onto the surface table, and sliding a feeler gauge between the notch feature on the shaft and the surface table.
The stack of feeler guages should slide to either extent of the notch with no difference.
If there is more than 0.001" difference, replace the shaft.
Alternatively, take the shaft to a machine shop to have the notch "squared-up" and fabricate a shim to place between the shaft and the blade to obtain perfect alignment of the blade, shaft and bore. Are the shaft (bushing bores) holes in perfect alignment?
Use a micrometer to determine the TB bushing inner diameter, and purchase an appropriate sized reamer to check the bore alignment with.
If the holes are not perfectly aligned, you could purchase some undersized bushings, and have them installed by a machine shop.
This is precision work that needs to be accomplished, so unless you have a good mill, send out to a machine shop to have done for you. Next you need to check the position of the shaft and throttle blade assembly within the bore of the throttle body.
With the throttle at idle position, verify that the clearance between the blade and bore (nearest the shaft) is symetrical on both sides using a feeler gauge.
Verify this alignment throughout the entire range of motion. Correct any misalignment of the TB blade to TB Bore by adjusting the shaft position, and / or the blade alignment on the shaft. You should also check that the Throttle Blade's chamfer matches correctly with the throttle bore. If the blade is installed up-side-down, this could cause the sticking problem.
The chamfered edge is what seals the throttle body bore when the throttle is commpletely closed.
Make sure upon reassembly that you get all of the parts (including the threads) surgically clean.
Don't forget to use LockTite on the threads! You wouldn't want to destroy your engine by having a small screw attempt to circulate within your running engine!
It sounds like from your post that things are reasonably close, so any defect would have to be determined using precision measuring equipment (micrometers, surface tables, etc.). Do NOT continue to sand or wire brush the bore of the throttle Body!
You should verify that the Bore is round and concentric before proceeding with any rework.
I'm no fortune teller, but I predict a trip to your local machine shop is in your near future! :) For my .02 worth, Its probably best just purchase a new set...
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11:28:16 05/10/11
