I have a 85 chevy astro van 2.5 that will start and idle fine but the exhaust manafold glows red in minutes there is not cats on it and the exhaust is not blocked the dash light showed code 42 so I replaced the icm but that didn't work it back fires and u can only get in 2nd gear 20mph to the floor I'm at a loss iv tried plugs wires coils icm grounds and vacuum lines iv pulled the exhaust off and let's put it this way I could use the flame that's comes out as a cutting torch