2001 S10 Xtreme Pickup 40,000 Original Miles,random Misfire Please Help

Ok here it is.... bought my truck about 2 months ago from a used dealership for 9500.Low miles, clean body,and clean car fax
but now its giving me problems.. first thing i did was put my amp and subwoofer in because the wires were already there. then i placed the ipod interface inside. all with stock radio. after about one week the engine throws SES. so i get home let the truck rest for about 30 min. start truck and get on the highway, while driving SES flashing truck not revving? take truck to shop and p0300 code comes up.. the shop says misfire and it needs a tune up.. shop estimated 700. for tune up with AC DELCO???? told shop no thanks and went to another shop. shop inspected all wires cap rotor and plugs. gave my truck a clean bill of health??
now today the truck puts and throw another SES i try to drive to shop but truck stalls and wont start? if any body can help with this post i would appreciate it.. by the way engine 4.6l w
with K&N air filter everything else is stock

Welcome to AF.
If light is flashing on the road you have cylinder miss or misfire.

Is on the road running fuel pressure up to par?
Try cleaning MAF sensor.

It needs to be put on a engine capable scanner to see which cylinder is missing and if all the time or just a ramdom missfire.
Check all sensor readings to.
And camshaft retard setting.

thank for the reply.. i put the truck in the shop and they said all cylinders were m/f and they also said that the cat was messed up. because of the cat being messed up the engine was getting to much back pressure. they said that this was the main cause of the engine not responding.t?f? well its getting fixed (full tune-up AC delco parts and a new cat) hopefully this solves the problem

well just to give everybody that looks at my post some more info
i talked to my shop today. they said that the problem was my valve came loose and cut off #4 valve so instead of a v6 i had a v5.. ha ha they said since the valve came off they have to replace the valves and pretty much change everything else. luckily i have an extended warrenty

Thanks for posting back how it went.
10-4 on the valves.
You have to have compression.
Let us know how it goes.
MT

so here it is the final talk with the shop.
they showed me what was the cause of the misfire and i felt happy and ticked off at the same time.. the root of the misfire was a stuck valve but what was causeing the valve to become stuck? it was a small piece of metal about 1" in size! and where did this piece of metal come from? the throttle body blade. its supposed to look like a half moon or something similar that shape. the piece came off the blade into the manifold and stuck between the valve spring on number 4 this is why the truck would run fine then bad. the spring would get stuck then come unstuck... what a crap shoot!!! ohh well i think the worst part was going into the shop and seen my truck in pieces :( but now its going to be all new... :) so thats it the whole problem, hopefully this helps someone in the future....

Thanks for posting back how it went.
Even thow it was bad news.
MT

How far did they have to tear it apart before they found the piece in the spring? Did they have the heads off and valve springs off before they noticed it?

they seen the piece of metal after the heads came off. the metal piece was really stuck in there. they only seen a corner of it. but they took everything off the block to inspect all parts to make sure nothing else was damaged just incase...