p0300 Tried almost everything....
2002 5.3L LS in a 1998 tahoe.
I have had a bad misfire from day one.... took my plugs off the ecm and checked continuity on all of the injector and coil wires... turned out 2 of my injectors were plugged into the wrong place. luckily they were pins not used... Inj 3 was plugged into the inj 2 pin and inj 2 was plugged into a dead pin. So I got that fixed and it ran ALOT smoother... Cleared the codes and drove it down the street and back... still hesitating and it died on me in my driveway.. Pulled the new codes... p0300 random misfire....
So here is what i did.
Checked each injector to make sure it was in the correct pin on the ecm.
#1 C1 - 36
#2 C1 - 4
#3 C1 - 3
#4 C1 - 44
#5 C1 - 76
#6 C1 - 37
#7 C1 - 43
#8 C1 - 77
checked 12V to each injector.
checked resistance of each injector 12.9 - 13.0 across the board..
checked signal wire for each coil to ecm. All are correct.
#1 C2 - 26
#2 C2 - 67
#3 C2 - 69
#4 C2 - 27
#5 C2 - 68
#6 C2 - 28
#7 C2 - 29
#8 C2 - 66
Checked 12V to each coil.
Checked ground to each coil
Then I found something interesting... Cylinders 7 and 4 seem to be the problem..
My headers are new and I let it run through a small heat cycle and the tubes off of those cylinders are still glossy paint where as all the other cylinders are turning colors due to heat...
So I checked resistance of those two coils from the output to the ground terminal...
I got 5400ohms for both which I hear is a normal reading..
So I tested my fuel pump.. Hooked up a gauge and got 52 psi at idle and no drop in psi at all during revving...
Fuel filter is new..
Plug wires are new...
I checked the plugs the other day and found 1 wet plug on the cylinder with the mis wired injector.. Replaced it..
Update... I also replaced all 8 plugs and no improvement. Moved plug wires around to see if the dead cylinders followed but nope still the same.. I even swapped coils for a good cylinder and the problem didnt follow..
Any ideas on what to do now?
Last edited by 2drhoe; 04-07-2014 at 06:54 PM.
98 Tahoe 4WD. 2002 5.3L LS swap.. Lowered on shackles and keys. 22" Escalade rims with custom SS centercaps, 2 tone red and gunmetal paint with silver pinstripe.SS front bumper cover.Rear roll pan. Street scene mesh grille inserts.debadged and demoulded.6K HIDs and hidden yellow fogs.Billet bowtie.K&N intake system. Flexalite Efans.Dual optima batteries. Pacesetter shorties High Flow cats. Flowmaster muffler with single exit exhaust. Escalade Seats and console. SS headrests. Remote Twin turbo build in progress!!!