Hurley00

iTrader: (3)

Hey guys I have a 00 4.8 and went racing the other night, turned the truck off to let it cool off a bit, started it and the fuel pump was whinning really loud. As I was leaving the truck started sputtering and the engine made a clacking noise, so I gave it some gas and it stopped at the same time the service engine light started flashing! When I came to a stop I had to keep on the gas or it was gonna die. I filled up with gas and had a 60 mile trip back home, made it home and it seemed better the light stopped flashing. Ran good for about a week and now things are going down hill Quick. Now my truck sputters up till about 30 MPH and at a stop it sits there shaking. Checked the DTCs and it said no. 7 cylinder misfire so i went a head and cleaned all the injectors on the passenger side and put them back, cleared that code and there was no difference it does the same as before and NOW I have a P0300 multiple cylinder misfire code! WTF!!! Ive searched this on here and found that,
1. Bad fuel pump
2. Clogged fuel filter
3. Clogged cats
4. Dirty MAF
Ive checked the connections and still no change.
ANY suggestions greatly appreciated.

sixltrbtr

iTrader: (5)

Could be a bad plug, wire, injector or coil. Unplug the coil on the number seven cyl and see if the engine runs the same. That will tell you if it's for sure number seven. If it's not number seven it will run worse when you unplug the cylinder. Try swapping the plug with another and see if the miss moves to the new cylinder. If that doen't work swap the coil. Then the injector. Make sure you have fire. If you can get your hands on a noid light, see if you have an injector pulse. If you move a plug and the miss moves to the new cylinder you know you have a bad plug. This should help you find out what is causing the running problem. Good luck.

00ChevyScott

iTrader: (10)

haha this JUST happend to me. Change the fuel filter ASAP, that is most likely the problem. Then throw in a can or 2 of B12 fuel injector cleaner, its cheap, like $3 a can at oreilly. Check all your plugs also, and put in some fresh gas.

viciousknid

iTrader: (8)

Add bad O2 sensor to the list. Hook up your HPTuners and check the O2 voltage. if one of them isn't fluctuating up and down then it is bad.

Hurley00

iTrader: (3)

alright im goin to try what yall have said, Ill let you kno what happens. Thanks

03chevyroyce

iTrader: (2)

same thing happened to me
changed the plugs and wires and everything was OK

foxySS

Look for a cracked plug.