Make sure the gasket is hanging over the open bore and the butterfly is hitting the gasket. Also spray some penetrating lube onto the shaft while opening and closing the butterfly. I little buildup of gunk will also cause that. Even blow some air onto the shaft and try to get penetrating fluid between the shaft and the tb.
hope this helps.
98 TJ,4.0, 5 SPD, 4' SPRINGS,RC 2.2, SYE W/ TW DRIVE SHAFT, JKS ARMS,JKS ADJ. TRACK BARS, CURRIE ANTIROCK, ACOS ADJ, REAR D44 W/ DISC BRAKES, 62 MM THROTTLE BODY, POISON SPYDER SLIDERS, LED TAIL LIGHTS, K&N INTAKE, THORLEY HEADERS, FLOWMASTER EXH,H4 CONVERSION, 35" BFG AT