My 94 park ave wont engage into overdrive. Also, when the car is warm and it drops down into 1st gearand coming to a stop. the car will lose power and stall out. But fire right back up and drive on.

Welcome to the forums Thomas.
Do you have a dash service engine light on?
The idle may be dropping after stopping, could be the IAC (intake air control )
Have you got the car in a good state of tune with new plugs, wires, fuel filter etc?
The car wont shift right either if it is bogging out, or experiencing misfires etc.
When hot, is the transmission fluid at the full line while in park. on level ground?

Yes. The service engine light is on.

You should be able to read the code or codes by using the paper clip test then.
https://www.gmforum.com/obd-i-troubl...p-test-306836/
The generic list of trouble codes are here:
https://www.gmforum.com/obd-i-troubl...eneric-306838/
Post back the codes that are stored please.

Ok. I will try it. Thank u so much for your time and knowledge.

So i tried it and nothing happend. I have 8 slots or pins on each row. So 16 total. Idk.? If it changes how the codes can be read.?

I moved the other post to trash on 1.5. Lets keep the information all in one place here please..
The paper clip test only applies to the 12 pin ALDL OBD connector.
You have the transitional year car.
An OBD 2 (16pin) connector, the OBD1.5 system.
You can make some calls to local shops,even Autozone, to see if they have the reader capable of this set up.

He'* looking at going to the dealer.

Dealet want 100.00 bucks to read the codes. No way.

Actron Super Autoscanner Model CP9145 9807 262 | eBay

Actron CP9145 is my favorite move for this problem. Essentially, any scanner must specify it is compatible with GM OBD 1.5 to get it to work.

Put the $100 to a scanner, and you won't have to worry again, instead of the dealership, if you do your own work. I have this same unit I got off of ebay for $40 (A steal) and have never looked back.