1991 Pontiac Sunbird stalling

Clean the throttle body and the iac. Check the maf and map, where applicable. Check for applicable trouble codes. Your obd 1, you should be able to check codes yourself, if your check engine lite operates. To check codes, place jumper wire between terminals A & B at the datalink connector, should be along lower edge of dash between steering column and driver door. After the jumper is in place, turn the key just till the dash lites come on, no further, no crank. The mil on the dash starts flashing, you count the flashes to get the codes. Your looking for two digit codes.

How long since a tune-up? You might also check for vacuum leaks.

What about trouble codes? Anything?

To check codes, the datalink connector should be located under lower edge of dash, between the steering column and driver door.

With the key on, just till the dash lites come on, no crank. Use a jumper wire between the A & B terminals at the datalink connector. Then the service engine soon lite on the dash starts flashing, you count the flashes to get the codes. Your looking for two digit codes.

Note the picture for location of A & B terminals at the datalink connector.

Because you already replaced some sensors, I'd erase the codes and see what comes back.

The code 12 usually just means your in diagnostic mode.
Code 22 is tps voltage low.
Code 33 is map sensor voltage high.
Code 35 is for the iac.
Code 45 is the system is running rich.

As far as the code 22, check the wiring connector at the tps sensor. Check the wiring circuits. Make sure the battery has a full charge. With key on, you don't have to start it, check for 5 volts ref at the gray wire. The black wire is ground. Also, check the signal wire/dark blue, use a digital multimeter. Move the throttle linkage up and down by hand, watch the voltage movement, it should move up and down smoothly.

The codes don't tell you what to replace, just that the computer thinks there is a problem on that circuit.

Because some sensors share ref voltage and ground, you have to be aware one sensor might cause an issue with another?

To troubleshoot the code 33 there can't be a code 22. The map sensor shows to be on the firewall close to blower motor.

Usually when you put the pedal on the floor, it is, "clear flood mode", too much gas. You need to check correct fuel pressure, use a fuel pressure gage. Some of the national brand auto stores used to loan out a fuel pressure. You may have to put up a deposit but, you get it back when you take the gage back.

Once you build pressure, turn the key off. See if the pressure holds for a bit? If the pressure drops like a rock, you have a leak somewhere.

It wouldn't hurt to give it a tune-up. Anymore, 02 sensors are part of a tune-up.

After you erase codes, did you drive it for a bit to see if any codes come back?

The code 15 is for coolant temp sensor, voltage high. A faulty coolant temp sensor can cause it to flood.

The coolant temp sensor should be in the thermostat housing or close to it. The wire colors are yellow and black. The coolant temp sensor lets the computer know the engine temp, and the computer will add fuel or take away fuel by controlling the injector pulse.