To retrieve diagnostic trouble codes (DTCs) on a 1991 Park Avenue, you can use an OBD-I diagnostic tool or a paperclip to short the diagnostic connector. The connector is usually located near the driver's side, under the dash. By bridging the appropriate terminals (often A and B), the check engine light will flash, indicating the codes. Count the flashes to determine the specific trouble codes based on the service manual.
On the intake manifold.
If your 91 park avenue is like the one I have. To the left of the radio is an air duct. To the left of the air duct is the adaptive lamp monitor module. The module is near the top inside of dash.
Go to GOOGLE and type in GM code reader 1.6 - All the answers you require are in the file that will appear - You don't need a code reader just a jumper wire
There is no EGR on the '91
If they are the exact same engine (3800 tuned port injection) then yes.
On my 91 its behind the engine in the center of the firewall
The belt drives the power steering, water pump, and other things.
No, The body style changed for both the lesabre and the park ave both years but while the Park Avenue's design was more bulky, the LeSabre was almost the same as before.. up until 2000 then the Lesabre's styling caught up with the Park Avenue. The Park Avenue and Lesabre were discontinued in 2005 The LaCrosse and Lucerne took their place pretty much.. My opinion is the 91-96 Park Ave/92-96 LeSabre looked the best ...and the front ends were interchangeable.
You can find Chilton and other repair manuals at your local library, you can copy the wiring diagrams at the library.
3.8 engine?? 1-6-5-4-3-2
5.25 in the front, 6X9 in the rear, for ALL park avenues 91-04, they have tweeters in the front doors as well
On my 91 it is located under the front pass door it run right along the frame