My car won't idle in any gear but park and neutral it seems. When I shift into gear it just fizzles out. Could a vaccum leak cause this? What are other possible cause?

Sounds like the torque converter clutch is out.

Do a search for diagnosing one.

I thinks Ogre has info in his cave also.

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Where will the road take you today?

Is it idleing too fast and dying when you put in gear, or idle too slow to keep running? Any codes showing with chk eng lite? May need to clean or replace IAC valve, spray down the inside of throttle body with FI cleaner. Past that, check the cave like he said.

i agree with both.
if it's idleing normal in park and then dies in gear, listen to hoho
if it's idleing low listen to roger

It's ideling to fast when in Park. Has a new IAC which has been tested and is function properly. MAP sensor code is given, but installed a new map and have checked all vacum lines all seem to be ok.

Idling fast in park sounds like vaccum leak

Unplug the MAP sensor connector and look into it and see what color it is (red, green,blue,black, orange) Make sure you have the same one that was in it originally. Mine had orange, and NAPA, and all the GM dealers all said the black was the only one made now and it would work. It didnt on mine. Autozone had all the different ones. (Im talking about the black plastic sensor on the top right side of the engine attached to the intake, rectangle shaped with 1 connector and vacum lines) I always get those damn sensors mixed up)

COuld also be another 30 dollar part...the neutral safety switch for the trans. And a real joy to replace.
Another two cent idea.
Red

My 85 V6 would stall going into DRIVE or REVERSE from PARK after a cold start.
I added a new ground wire from battery to engine block ( a la $RICH$ ) and resolved the problem.
Might be worth 5 min. to try it.

I would agree with JT on that one, sometimes a bad ground can mess you over