Fouling out plugs

[03slowverado]

Ive got a cammed 5.3L with a custom air intake and when i swapped in new plugs i realized that all the plugs on the passenger side were being fouled out. Even when I put in the new plugs it would kill them too, any suggestions. Thanx

[tbplus10]

First read the computer for any stored codes.
When you say cammed whats the lift and duration?
Could the grind be to much?
Custom air intake?
Has the computer been tuned for any of this?

[03slowverado]

Well the cams been in since '04 so i cudnt tell u the lift or duration, but it used to run great. And no tuning has been done. The "custom intake" is just 4" pvc I modified to fit from the air box to the TB, nothing major. I was kind of thinking the problem lies in the fuel system. Maybe a fuel pressure regulator or injectors. Its just strange to me because its ONLY on the one side.

[tbplus10]

How long have you had the custom air intake on, could it be a combination of the cam and intake?
Also have you done a diagnosic on the computer to see if it has any issues?
The fuel pressure regulator is in line and would affect all cylinders and injectors.
I'm thinking something in the systems telling the injectors to squirt more fuel or the injectors coul be dirty and not closing all the way allowing excess fuel in the cylinder at the wrong time.

[2COR517]

If you want to throw parts at it, start at the O2 sensors. The engine controls mixture for either side as a group. So if pass side reads lean, it will add more fuel to all of them. Just primary O2 sensors, the rears have nothing to do with fuel management. O2 sensors can "wear out" over time, and should be considered tune up items and replaced every 60-75K. And since it's been running rich, it's probably even more gunked up and ready for a change. Also, make sure you do not have any exhaust leaks. They can cause a false lean to the O2 sensor, which would have the same results.

[Rocketman540]

03 slow. If you have a scanner it would be helpful to know the short term and long term fuel trim numbers.

Verify o2 are switching ok.
Somtimes a dirty mass air flow sensor will skew readings as well, you can contaminate them if you over oil the air filter, but they can be claned with some electrical contact cleaner.
Make sure the plugs are gapped correctly
Check for codes.

[vncj96]

When you say fouling what do you mean, they are just blackend or are the electrodes getting burnt down. I had the same thing and it was a bad valve. Result was rebuilt both heads.