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P0420 code! WHATTT

dmahlikGT

dmahlikGT

New member
For a few months now my check engine light has been on.I had a head job done back in may due to the infamous coolant leaking into the heads.Since then I have noticed a problem getting slighty worse by the weeks.when I start up my car it idles crappy until its warmed up. Then if I step on it at about 2-3 gear or 50-60mph it starts hesitating and jerking for more speed.Always happens.Seems to happen faster and worse when the car is hotter.I had the code read a few weeks ago and it was p0420.I changed my cat.im thinking either o2 sensor or fuel filter.Any ideas?
 


Usually that code it related to your gas cap being bad/evap system it could even be a bad purge solenoid or vacuum line off the engine.
 
hmmm.those sound like possibilities especially the MAF.I'll see try those if the problem still persists.thanks guys
 
Oh also when I got the code scanned it specifically said catalytic inefficiency/bank 1 or something like that.Not sure if that makes a difference.
 


I just had a P0420, it means it is time to replace the CAT. It also means that both of your sensors, before CAT and after CAT are working fine.

I had a "heavy metal" CAT from flowmaster installed, the shop cleared the code and it has not come back. Cost me $285.00
 


nope guys.the mis was a simple fix.my spark plug heat sheild was sparking with a bolt which pulled from the spark plug itself causing the mis.lol.i just took it off and it pulls hard again with no mis.back to the p0420 code,would a bad 02 sensor cause the engine idle to surge a little when accelerating?
 
A highflow cat can kick a 420 code rear o2 can kick a 420 code and so on
high flows arent as efficient as standard cats so it will still kick the code on some cars

Also depends how your tune is to test sscan your rear o2 sensor it should stay steady under 400 mili volts
if its higher or bouncing around thats your issue
 
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