Hello, I just bought a 1995 Park Avenue Ultra, for $1000 has 196k, decent shape, it runs great. But im experiencing a plethera of issues. I bought it about an hour and 20 mins from home, drove it home on the interstate no issue, but now its giving me hell. Im experiencing a severe power loss and the transmission wont kickdown into a lower gear say to pass or anything. I replaced the vacuum cannister and the modulator on the front of the tranny from a junkyard car and it seemed to help then it did it again or rather didnt downshift on command. Also it seems like it has low power, when i first got it it was great i was happy as could be. Now it just doesnt seem to have that pep in its step. Ive only had it a week and have had alot of things pop up and ive addressed them such as new ac compressor, burned crank sensor wire (had to put in new pigtail connector) it locked me out of itself (not the doors) it tripped the anti theft, had to do the resistor trick to imitate the resistor in the key. If anyone has any suggestions on the no kickdown please let me know, Thanks.

is it the sc engine? any codes? check fuel pressure? look at normal maint. stuff see if the fuel filter, air filter, plugs, wires have been changed recently?

Yes it is supercharged. It has a check engine light on. Has brand new ac Delco plugs and new wires with maybe 200 miles on them. Guy I bought it from put a cold air filter system on it and it looks like its brand new. I don't know about the fuel filter. It seems that when cold it does downshift but warm it won't.

Check/Clean MAF sensor. This involves removing it and spraying it with a cleaner that is SAFE for MAF sensors.

Then check your TPS sensor.
https://www.gmforum.com/trouble-shoo...sensor-279319/

pretty much guessing until you read the code for check engine light

Yup, get that scanned. More than likely dealer only unless you know someone that can scan OBD1.5 and 2.0. Autozone can't touch the 1.5'*.

What is the maximum boost you are getting at WOT?

My uncle has a Snap On scanner that reads OBD 1.5, past history codes are prndl switch failure, tps high, and qdm 1 failure. When he was looking at it it was working just fine, now its not working again. I replaced the tps with one off my brothers Bonneville SSE old engine that blew up. no change, the tps was reading weird on the scan tool, it seemed jumpy, i did clean the MAF sensor with MAF cleaner. No change. It has a mind of its own, sometimes it works as it should and downshifts and i can pass, but most of the time it wont it just boggs when i step on it. I dont have a boost gauge in this car to see how much its putting out at WOT

I also forgot to mention that when it acts up my overdrive does NOT kick in, it shifts up to third and then stays there. If that helps at all?

you take out the plug for the trans check it out and reseat it. qdm is ussually a wiring issue with the pcm'* power circuit for sensors and that