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Discussion Starter · #1 ·
Hello I'm new to the forum. Hope i'm posting this in the right spot. I have a 1997 s10 pick up with a 4.3 and can not get the po300 code to go away. Code only shows up under medium to heavy acceleration. If you baby the truck code does not appear at all, but you can sense some hesitation. When you accelerate hard you can feel the motor hesitating and misfiring. SES light flashes and stays on for about a day, then computer clears itself out if you do not accelerate hard. Here's a list of things that i have changed already which has not gotten rid of the code, but has made the truck run better:
  • new EGR valve and new line to manifold
  • new updated FI spider with new FPR
  • new throttle position sensor
  • new delco plugs
  • new gold plated cap and rotor
  • new MSD coil
  • new fuel filter
  • replaced fuel pump assembly 2yrs ago
  • brand new magnaflow CAT and O2 sensor behind cat
  • new fuel pump relay
  • new PCV valve
  • changed and added new ground cables
  • checked and cleaned MAF sensor, also replaced with brand new one, stock one works fine
Tired of throwing parts at it. Hope somebody can help me. Mike:doh:
 

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goin broke but n style
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PO300 is for multiple misfire.

Install a fuel pressure gauage and go for a drive. Watch to c what the fuel pressure is when it starts misfiring.

Also check for vaccum leaks. a vac leak will/can cause a multiple misfire. Look at thre crank sensor for any contamination. It may be damaged or the wires frayed.

Is your truck loosing coolant. if it is you may have a failing intake gaskets and its sucking coolant into the engine. If it is silicone is an O2 sensor worst enemy. silicone kills O2 sensors.
 

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Discussion Starter · #3 ·
Hello ,I also forgot to write that i replaced the crank sensor and the cam sensor,coolant level is always the same ,i will try to test the fuel presser the hook up is before the fi spider and fpr so if theres a problem what could it be?
 

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could be the pump or a hose in the fuel tank or it could be the FPR or the spider
 
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