03 GMC Yukon P0300 misfire 5.3

[Jeffs5-3]

This is my old spark plugs I had replaced the other two I have no clue where they are

 

[Fless]

Although they don't look too bad they look like they're old school copper plugs. Hopefully you replaced them with at least double platinum or better.

 

[Jeffs5-3]

Although they don't look too bad they look like they're old school copper plugs. Hopefully you replaced them with at least double platinum or better.

I replaced them with some NGK iridium ix plugs. I also cleaned the maf sensor as well

 

[saintdominic]

Working on my 03 Yukon with the same issue today, only P0300 code. You find your problem yet?

 

[Jeffs5-3]

Working on my 03 Yukon with the same issue today, only P0300 code. You find your problem yet?

Unfortunately I never got to resolve the issue as I have unfortunately lost my truck due to an accident, lady had ran the light and I unfortunately ended up getting hit by her and another car from the rear she totaled my truck sadly

 

[Jeffs5-3]

Unfortunately I never got to resolve the issue as I have unfortunately lost my truck due to an accident, lady had ran the light and I unfortunately ended up getting hit by her and another car from the rear she totaled my truck sadly

 

[29tomt]

Hello everyone I have an 03 Yukon with 5.3l L59 171k miles on it and it’s been a love hate relationship with the truck tbh. I have a dreaded misfire that’s just been kicking my ass and i want to address it because I want a reliable daily. I bought the truck about 2 months ago the truck had given me a reduced engine power message but with no check engine light I figured it would be spark plugs so I changed them out perfect I then went ahead and changed out the wires while I was at it. The truck ran good somewhat I figured I still had a misfire because going down from 2-3k rpm I would hear the engine backfire a lot. Yesterday as I was heading home I felt the truck didn’t want to accelerate as much as it would normally and then it started shaking and idle very rough then check engine light came on first flashed me then it stayed lit I pulled over I turned it off and waited 15 seconds. I’ve dealt with reduced engine power before but the message never came I tried to turn it on but the motor just sounded like it was struggling to start up and crank over it started coughing and sputtering I thought the worst of the worst and was like shit what now I waited a bit longer I managed to get it started okay great went to autozone that was down the street scanned me the code and there it was P0300. I love the truck but I just want it to run right I’ve been looking online saying coil packs, air intake manifold gasket, fuel injectors, 02 sensors, air filter, fuel pressure, all those things but obviously no solution so before I go ahead and start buying and just replacing everything I want to pin point it to one thing. P0300 is the only code that popped up no other cylinder or code besides the abs malfunctioning but I had that already but the damn dreaded p0300 is making me just wanna get rid of this thing your solutions will be greatly appreciated and looked into!

My 2003 Tahoe played every trick in the book including rough idle, no crank, crank then shut off immediately, etc until I replaced the MAS after having cleaned it and the throttle body. Engine has run as new every since and has 224K on it now.