2003 silverado 2wd 4.3 litre P0300 code

ryn0909 · January 16, 2012

I have an 03 silverado 2wd 4.3 litre v6 that suddenly developed a serious misfire. The CEL came on and i plugged in my code reader and it showed 2 DTC's, both are P0300 Random Cylinder Misfire. This happened a couple days ago when i used my truck to ATTEMPT a jump-start on my 98 Ram cummins pickup. After 2 failed attempts i disconnected the jumper cables and got in the truck to park it in a different spot. It started to missfire a little, then progressivly got worse. At first i thought i was running out of fuel so i poured 2 gallons in the truck, fired it back up and the misfire was even worse. Once i realized it was a random cylinder misfire, i suspected the coil to be faulty and replaced it with a new one. At the same time, i also cleaned my MAF sensor, double checked for loose plug wires which all were ok, and it didnt make a difference whatsoever, still misfiring just as bad. Im not sure if wether or not the jump-starting is the cause of the misfire, or if it is just happens to be coincidental. Anyone ever come across a situation similar to this? Any ideas on what it could be? i guess really my main question would be wether or not it was caused by the jump-starting...... any assistance is greatly appreciated... thanx

markw8 · January 16, 2012

How long has it been since the cap and rotor were inspected or changed?

Mark

ryn0909 · January 16, 2012

I just checked them last nite and they are good. I changed them about 10k miles ago.

ryn0909 · January 19, 2012

also The engine starts easily, but it just has the damn misfire. from idle to about 3k rpm the misfire is very noticeable, at 3k rpm and up the misfire isnt AS noticeable, but it still exsists.

-the fuel pump comes on and sounds like it normally does. i had an assistant turn the key on for me and i pressed the valve at the test port on the fuel inlet line and it SPRAYED a good amount of fuel out, so im guessing there is enough fuel pressure.

txab · January 20, 2012

That's not an accurate test. Test fuel pressure with a gauge. A few PSI too low and you can have problems

ryn0909 · January 20, 2012

yea, yer right and i know that too......lol ive gotta borrow one cuz i aint got any money to but one..... lol ill post any updates between now and whenever i get one....