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whats wrong! wierd shuttering after 4k

i recommend cleaning yoru throttle body, running seafoam threw the car via vacuume and gas and also changing your fuel filter and pcv valve
 


i think i found the issue... the front plugs were the acdelco...rear were bosch platinums...alll burnt and messed up...putting new plugs in now.. ill keep u guys posted
 
it is.

but heres a pic for the hell of it.


plugwires.jpg
 
new plugs installed... problem might have even gotten worse. it does seem to run better as far as b4 4k rpm but at WOT it hesitates even more. and my catalic converter sensor went on.. p0420 code
 
theres the cause, your cat is clogged up, that will make the cel flash as well. and cause the misfires. flashing cel means a catastrophic event going on there.

so dont beat on it till you get a new cat.

to confirm this, you can pull the upstream o2 sensor, if it runs better even with the monster exhaust leak, the cat is clogged up for sure. taking the o2 out lets the engine exhale through the leak you just made by taking the o2 out. you want the one thats in the rear manifold, the one that gets in the way of changing the plug back there.
 


ok the cel isnt flashing but it did come on and said something about rear bank threshold breached or something along that effect....so pull the 02 sensor thats aboce the downpipe?
 
also.. every car that i have owned when the cat clogs the car usually doesnt run hardly at all not just over 4k and usually any problem ive had at 4k or above become a ignition error...
 
P0420 Error Code: Catalyst System Efficiency Below Threshold (Bank 1) could be the cat from what this link says for the code you posted.

you want the upper o2 removed for a test drive. the one thats in the way when your changing the rear plugs.

you can also see if its glowing at night, and you can hit it with your hand when its cold and listen for stuff rattling around inside it.

the engine will sound like a vacuum with a full bag too like it cant suck in any air.
 
Well, now you get to get yourself a new downpipe! :)

4 bolts. Not hard.

Oh and probably a new PCM if your new DP/cat is high flow.... that 0420 code will never go away if it is.
 
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