I've got a 2003 Yukon XL it had a knock sensor code come up so I ordered knock sensors Delphi knock sensors GM wiring harness fel-pro gasket kit I didn't buy any of the cheap crap. Anyhow the day I got everything in it threw a code po300 which is multiple cylinder misfire. Tore the motor down that day. I cleaned intake cleaned fuel rails out come to find out I had water in my gas and I cleaned all the fuel injectors out checked everything made sure everything was good. Put it all back together it turns over but won't fire like I act like it wants to start but it doesn't start. I've checked everything made sure everything was plugged in I don't know what else to do
Acts like it wants to run but doesn't.
- Thread starter NO4NSHIT
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wjburken
Supporting Member
Since you tore apart part of your fuel system, might double check all of that and make sure you have good fuel pressure.
Well I've just done that.. and realized my fuel pressure regulator is leaking a little bit popped it off and reinstalled it correctly now it started to start but was really crappy sounding and then died scanned it again and it came back with po200. Pressed the check valve on other side of fuel rail got nothing coming out of it. So no fuel pressure which is my problem but last night the fuel line that ran that runs from the fuel filter to like a some type of other valve or regulator whatever underneath the truck and then another line goes off of that up to the fuel rail with a small line from the fuel filter to that regulator whatever it is it screwed up on me and I couldn't get it off the filter and I realized that one of the little tabs on the inside was messed up so I replaced it with a piece of fuel line that I had and I had to make it a little bit longer of course because I didn't want me cuz it's not the same type of fuel line it's the same size but it's a little bit longer don't know if that really means much..
I've cleaned out the tank blown out all the line cleared all water from fuel system. I've replaced the fuel pressure regulator spark plugs cuz they were fouled out. Replaced the knock sensors intake gaskets leaned the throttle body and fuel injectors. She starts up ran ok for about 10 seconds and then started running rough and backfiring out tailpipe so I then shut it off and am now at y'all mercy.. idk what To do... It didn't throw no codes so I'm confused on what is wrong..
So after I replaced the spark plugs I started it up and ran it for about 5 minutes and it started to run like shit then SES light started to flash and I shut it off rechecked the spark plugs started on number 1 it was ok but number 3 and 7 were black as night. I wiped 7 off so I could see weather I could clean it or not.. And number 5 had just a slight discoloration on it from looked to be like oil.. now I don't know jack shit bout the LS motors so please help me.. 
I'm having some problems I had a had some water getting my gas tank somehow not really sure exactly I've cleaned it all out and I changed the plug change the knock sensors place intake gaskets clean the tank out feel pressure regulator I put new plugs in it started it up and I mean within about 7 minutes of it running it turned my spark plugs to be black on number 3 & 7 I haven't checked the rest of them but I'm just curious as to what it could cause it it's really shaky missing real bad it throws up the code po300 I'm lost I checked all the fuel injectors I'm getting the ohms that I should be getting and they were all cleaned recently and checked I don't know what else to do
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Snowbound
Jim
Wouldn’t that be #1 and #5 or is it not in a particular order?
just because the injector ohmed in spec doesn’t mean it isn’t dumping fuel. That just means the coil to open the pintle is good but the pintle seat could be damaged. They sell a cleaner that screws right to the fuel rail and pressurized the injectors and blasts thru them. I’ve heard good things about it. Might want to give it a shot.
just because the injector ohmed in spec doesn’t mean it isn’t dumping fuel. That just means the coil to open the pintle is good but the pintle seat could be damaged. They sell a cleaner that screws right to the fuel rail and pressurized the injectors and blasts thru them. I’ve heard good things about it. Might want to give it a shot.
My pops used a 9 volt battery and cleaned them all 2 days ago. They all passed his inspection.
