The car has a bad misfire wont accelerate go up hills drives like its not getting fuel.I changed spark plugs & wires it made no difference.I got tired of F%^ing with it and took it to a shop.They say it needs a new cat converter...only $500."Too much back pressure killin it"(their words) The question is would a bad cat cause the car to misfire????>They checked the coils injector ect...all fine


2001 firebird 3.8 v6


A week ago i was started the car and was listening to the motor trying to figure out what that weird noise was.I turned on the air conditioner and as soon as the compressor started it almost killed the engine.That is when the misfire problems started

 

A clogged cat or exhaust can cause misfires because burnt gases cannot exit the engine. When the plug fires there is nothing that will burn, so it is a misfire.
P0420 means the cat is bad and not cleaning the exhaust
P0305 means that cyl 5 is misfiring. Could be ignition or a lean condition, possibly a clogged injector

 

That seems real high for a cat, autozone has them for 60 to 100 dollars, you could then take it to a shop for them to cut off the old and weld a new one. they should not charge much more than 70 bucks, just a thought.......SFC

 

I took the car to a different shop and they actually tested everything.......The problem was weak spark from coil #2-5....problem solved. Now i can get back to driving it like i stole it..........