Enigine making weird noise/check engine light on

[Manitoba GMC]

I've got a 2000 1500 4x4 with the 5.3 it's got about 100000 miles, lately it is doing something a little strange, it runs great at lower RPM and performs as well as it ever has. The problem is when I really walk on it ,it doesn't accelerate like it should and it starts to make a rattling/pinging noise and then the check engine light comes on. I had it scopped and the only thing that came up was "plug #3 mis-firing" I replaced all plugs and wires with no change. I've also checked fuel pressure at full throttle and it stays at a consistent 55 PSI. I'm looking for some advice, has anyone else run into this? Thanks in advance.

[GM-Tech]

No, it doesn't say PLUG #3 misfiring, it says cylinder #3 misfiring. Whole different thing. It doesn't know why that cylinder is misfiring, only that it is.

 

It could be a plug or wire, but it could just as easily be the injector or even a mechanical problem.

[RDWCO]

Have you ever changed your fuel filter? If not it could be your problem and if not changed soon could kill the fuel pump inside the tank.

 

RDWCO

[bobcat5544]

first off it is not you fuel filter.

 

a # 3 cylinder misfire could be caused by 1 more more things

 

# 3 spark plug, # 3 spark plug wire, # 3 ignition coil /or wires to the ignition coil, # 3 injector / or wires to the injector, intake or exhuats valves not sealing, a seized # 3 piston rings...

 

these are the most common things that will cause just a # 3 cylinder misfire

[Manitoba GMC]

first off it is not you fuel filter.

 

a # 3 cylinder misfire could be caused by 1 more more things

 

# 3 spark plug, # 3 spark plug wire, # 3 ignition coil /or wires to the ignition coil, # 3 injector / or wires to the injector, intake or exhuats valves not sealing, a seized # 3 piston rings...

 

these are the most common things that will cause just a # 3 cylinder misfire

 

<{POST_SNAPBACK}>

 

 

 

Thanks for the tips, I've run a fuel pressure gauge after the filter and I get a constant 55psi under load at WOT so I don't think it's a fuel pump or filter issue, I've replaced the plugs and wires so I'm sure that isn't the problem. I supose my next step will be swapping coils and see if the problem follows, that and a compression test.

 

And now, possibly the dumbest question I'll ever ask, sitting in front of the truck facing the engine, which is cyl # 3?

[Schwag]

Manitoba,

 

cylinder 3 is the 2nd plug from the front of the engine on the drivers side...

 

 

-steve

[mmmikkke]

Did you look inside the combustion chamber when you had the plug(s) out? If it's seriously carboned up, the hot spots that were/are causing the detonation (pinging) might still be there, even though you gave it a new plug and eliminated the cause of the carbon.