hey guys , anyone ever suspect there cat being plugged, and throwing a 303 misfire code------f150 super crew 140k 5.4 she started to buck shutter what have you,,,no codes, trany shifting irratic. then for a week it was fine.. yester day got the same symptoms no code,, i kind of got on the gas a little and she tossed a code finnally. bad smell from exhaust.. or does the pcm take that long to toss codes--------- thanks mike

 

Misfires usually take a while before they'll throw a code. Most feel the shutter before a code is seen. With those miles I'd probably just go through and change plugs, O2's, and cats.

 

thanks------- i changed plugs over the summer, and put on cat back duall exhaust-----what i did notice is the pip egoing into the muffler is burnt thru- man thats got to be hot.. im going to switch out the coil to cyl 1 to see if it trips that one. might have to cut the pipe around the cat to see if its bad. thanks for the reply mike

 

Sounds like you have a coil pack shorting out. You could remove the wires one by one, or wait for the code. When you pull the coil, dry it out good, & spray with some contact cleaner. Then add some Die-electric grease inside the coil boot, & some around the top part to seal it off.

All of the winter moister will drive your coil packs crazy!

 

ill try that thanks

 

Agree, PCM's are slow to throw missfire codes. I would think the 02 sensors would be throwing codes if they are failing, likewise for the cat being bad. You might consider having the emissions tested before replacing cat, unless its welded to pipe that has hole.

BTW, the exhaust can't have holes to be tested, it needs to be tight, can't be sucking air from someplace.

 

i switched 1 and 3 coil. truck still shakes like its restricted. no code yet after that. it has power just seems to be held back

 

If its a P0303 code it a cylinder #3 misfire and a bad converter will throw it. This is one of the sites I like to use to get the causes and cures for OBII codes

http://www.obd-codes.com/trouble_codes/

 

thanks--- im cutn the pipe before the cat going to take a peek

 

well still buckn and shakn-- no code after change around----i dont want to cut the pipe to peek in-- can i remove the o2 sens. infront of cat to relieve pressure. i know it will trip a light . thanks mike