02 3100 170k So this post is probably gonna be a long one. I bought a malibu a few months ago with 170k miles for good price on the condition that it has a blown intake gasket. Car could barely get moving, up until about 40mph(you can forget about highway speeds) it will jerk/hesitate and misfire till which it will eventually get better after awhile. Was told the intake gasket was the reason it doesn't drive good. Had the intake gaskets replaced recently to fix the disappearing coolant issue, huge oil leak and misfiring...only thing is it only semifixed the coolant and oil issue. Still misfires and drives like garbage, as well as the water pump starting to leak and squal badly which is just perfect. According to the mechanic, the catalytic converter is also bad hence supposedly cuased by the intake manifold leaking hense why it drives like garbage. codes are p0300(misfires)and p0404(egr flow insufficient). this morning while watching it run I saw some fluid boiling and escaping the front of the block(something I noticed well before I had it repaired) and I'm wondering if the exhaust manifold gaskets are also bad. Has new Egr, Maf, sparks and wires, and maybe Iacv. Runs and idles pretty rough. Pic was from where it was coming out(can't see it in action all the time). Cars pretty loud too despite an intact exhaust. So what are the odds that the catalyticconvertes bad? *side note* for whatever reason they use red dexcool maybe cuase its supposedly better idk.

Typically see bubbliling or leaking fluid where the furthest right bolt is, as well as smoke in some cases.

 

If it was burning oil fast your cat is probably gone, I'm guessing but you likely need the head replaced at the least, as well as a new Cat. Did any coolant leak into your engine?

 

It was the catalytic converter, had it replaced today and sure enough all the symptoms I was having listed here went away! for all who may have the same problem:
P0300 multiple misfires
p0404 egr flow insufficient
terrible acceleration and chugging(getting up to 40mph was a chore, timed for me was 25 seconds! )
awful gas mileage (10 mpg or less)(I got 5mpg on average)
trouble starting, rough idle, misfires felt when running
engine noise is much louder
Exhaust backpressure will build up, resulting in blown gaskets(i.e exhaust manifold gasket)
does not have to have p0420 catalytic converter flow poor code for the catalytic converter to be the issue. This problem has been very frustrating but finely has been fixed and hopefully this helps anyone having these symptoms.
oh and as for what caused the catalytic converter to fail was the intake manifold failing causing the coolant to flood the cat cuasing crystallization destroying the flow of the exhaust