P0300 random/multiple cylinder misfire detected

SOURCE: catalytic converter still glowing red

When running does the engine shake back and forth (indicating a skip in the engine) also does it rev up freely. If you were to rev it up to 3500RPMS would it be smooth without the engine shaking back and forth? Also the o2 sensor on the front of the exhaust manifold is pretty easy to get at, if you were able to pull that( 7/8") wrench I beleive) you could tell if it were running rich (sooty black color). In the end you could take it to a muffler shop and for very little money have them inspect your cat, without any cutting or welding. a $20-$30 cost at most. I know the fixya wants us to be self suficiant but even i don't mess with small exhaust work because of the benieft of not dealing with it, especially for such a small price. But if its something you wanted to do, I could explain so. A shop can visually inspect the cat, and see if it is clogged with oil, or excessive fuel. At any rate in the end if they do find that you do need a cat, don't buy a GM one, there are plenty of other sources for an aftermarket cat. IF you decided to go that route i know of a few sources that one could be had for pretty cheap ($50-70) for new. Let me know if any of this helps

SOURCE: put a checker on it and got a p03000 random multiple cyl misfire

you are getting a misfire and 99% of the time you need a tune up
plugs and wires and clean your throttlebody

SOURCE: 98 Chev Lumina LTZ

I have had the same issue..

I solved it by replacing the Manafold Air Pressure sensor, and the Mass Air Flow sensors, has not had a problem since.

The parts are fairly easy to replace yourself if you are mechanically inclined, however if you do not feel comfortable in doing this work yourself, take it to the shop.

My dad had the same issue on his Buick, and after the factory replaced coil packs, plugs and wires, they finally decided to change out the MAP sensor and that fixed it for him.

SOURCE: the computer says Random / muliple cylinder misfire detected

look for a vacuum leak

SOURCE: multiple cylinder misfire detected

Thank you for all the information. I don't see how you made it worse unless the injectors were not installed correctly. If you remove them you are suppose to replace the o-ring on each of them and oil them (the o-rings) before installing them. I would check the air filter and the CAT (for excessive back pressure. Also check the rest of the exhaust for damage. If a pipe is kinked or flattened it would need repair. Also GM's are known for some issues with there e-vap systems. You may want to check it out. The gas cap, charcoal canister, vacuum lines. Well good luck.