1997 Jimmy/ High Idle & Erratic shifting

New Here & let me say... Great forum!!

My problem is as follows,
I replaced the intake manifold gaskets about a week ago. (4.3 V-6 )
No problems at all, (no coolant leaks, overheating, or engine idle/performance) issues. Until this morning I started it up, the idle was at or around 2000 rpm & never Idled down till I put it into gear,
On the road the Tranny wouldn't shift until the RPMs reached 3000-3200 RPMs
No codes ( no "check engine" light) as of yet.
Pulled into work & put it into park & the Idle was normal,
Shut off & restarted it... right back up to 2000 RPM
Any Ideas??? :confused:
I'm at a loss here any & all comments welcome

Ign switch?
Check engine light on?
Have it checked for codes and post back any codes.
MT

Well... she finally threw a code on the way home from work, about a mile away from auto zone, Had them read the code..
Ended up being the throttle position sensor (only code thank God)
So long story short..
$41.00 and about 25 min. later... Problem solved..:biggrin:
Thanks for the reply.. like I said before.. you guys have a GREAT forum here.
Thanks... & keep up the good work..

Well... she finally threw a code on the way home from work, about a mile away from auto zone, Had them read the code..
Ended up being the throttle position sensor (only code thank God)
So long story short..
$41.00 and about 25 min. later... Problem solved..:biggrin:
Thanks for the reply.. like I said before.. you guys have a GREAT forum here.
Thanks... & keep up the good work..

You are welcome.
Thanks for posting back how it went.
Glad you found the problem and all is well.
MT