1985 firebird 305 tpi wont pass smog. changed maf,ox sens,catalytic conv,fuel pump,adjusted valves, need to know how to do

change your oil and oil filter. Add a bottle of octane boost to the fuel tank then top off with fuel. Drive vehicle for about twenty minutes then have emissions tested. Unless you have a bad catalytic converter, you should pass emissions.

the security lamp has nothing to do with the running of the veh get it scaned for dtcs

sounds like a bad catalytic converter, just did my 1985 Jeep could not get it to pass ended up replacing the catalytic converter, muffler, ox sensor and EGR valve then Jeep passed with flying colors.
if your cat is bad it reduces your exhaust flow causing loss of power and increases fuel consumption.

Hello! when you say you checked the MAP sensor what do you mean? Did you take voltage readings at idle ? A vacuum leak is the likely culprit, especially to the MAP...The minor shake at idle being the major clue...Send a comment...guru..saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Remove the exhaust system from the catalytic converter back
Remove the exhaust pipe heat shield and the exhaust muffler heat shield
Remove the rear axle assembly.and so on..............

88 you need to drop the tank

Basically what he does is pressurizes the tank and all the lines up to the charcoal cannister.
Anywhere from the hose from the filler neck to the tank could be cracks or loose clamps.

The top of the tank has a seal for the fuel pump and rollover valves. These are rubber and could be leaking.

Under the hood you will see the charcoal cannister inbetween the radiator and engine on the passenger side. The hose could be unplugged or cracks. Or the cannister may of failed. The cannister is unseviceable
except for the valve thats on it if it has one.
You could spend a couple hours trying to find the problem especially if it on top of the tank.

What the shop will do is pressurize the tank again and with the smog machine sniffer they can stick it where you can't access to see if it can smell fumes.
Takes a shop 10 minutes to find the area if you want to know.

If it is fuel injected,the fuel pressure regulator is most likely the problem,if it is carbureted the mc solenoid could be the problem,or carburetor needs rebuilding.

Could be a thermostat. Try changing the thermostat and get it too operating temperature and see how it goes. Only have limited knowledge of mechanics but hope this at least helps in some way :)

You didn't say the year? But check the coil. Frankster016