SOHC Diagnosis... lend ideas to try..(spark plugs-check engine)

[speed3000gt]

****UPDATE**** JUST WANTED TO POST WHAT RESOLVED THE PROBLEM...
I put some Berryman Fuel injector/fuel system cleaner in the gas and changed the gas cap and the light went away.... So I dont know which one it was, but im happy as hell!





I wanted to see what other ideas yall could throw at me to try with my problem. First ill start with the car's background:
'99 SOHC, currently 178k miles.
I got the car with 171k and replaced the spark plugs about 1 month later with some NGK BPR5ES-11 . About 2 weeks later the check engine light popped up and i didnt think much of it because the car drove fine/ as normal and thought it might just have something to do with the TSB on '99 3000's check engine light appearing for no reason.
I took the car to Autozone, the following code came up :
P0421
Definition: Catalyst Efficiency low bank 1
Explanation: The oxygen sensors monitor the catalytic converters ability to store oxygen
Probably causes
1) Catalytic Converter defective (Failure possibly due to #2, 3, or 4)
2) Engine misfire or running condition
3) Large vacuum leak
4) Engine oil leakage into exhaust-valve guide seals, piston rings.

Fast forward to current day: Car has 178k miles. (7000 miles on plugs)
So last week, I take out the front 3 spark plugs to inspect them and do a mild rubbing off of whatever's built up on them.. I put them back in and bam, the check engine light went AWAY! I was so relieved, but my dumb ass wanted to go one step further and just replace all 6 spark plugs since I thought maybe it had something to do with the plugs.... Well I go to autozone and they sell me some NGK V-Power plugs ( part number bpr5ey-11)
Is it just me or do these suck? My Check engine light came back.


I thought maybe the spark plug wires had something to do with it so i got some borg warners to test out and that didnt help.

Im confused as to what to try next. My car DOES have an oil leak, somewhere from behind, like the rear main seal...... could that have anything to do with it? Here are some pictures of the plugs with 7000 miles on them.. Sorry, I know they are CRAPPY quality, but according to the NGK page on reading plugs (http://www.ngksparkplugs.com/techinf.../faqread2.asp), it seems like reason # 1 or possibly #4 if i had left them in longer.

Should I get some brand new factory plug wires and brand new factory plugs and see if that gets it done?

BTW, would the autozone reason #4 "oil leakage into exhaust valve guide seals / piston rings" Cause smoke? my car doesn't smoke at all.




Thanks for any input

[Stealthee]

I dont think the plugs have anythin to do with your CEL.

The CEL sounds like one that would be thrown if your precat was gutted or the precat o2 was failing.

[speed3000gt]

But the thing is, everytime I replace the spark plugs, the check engine light goes off for about 10 miles, but then pops back on..




UPDATE
Fuel injector cleaner and replacing gas cap has fixed this check engine light problem!!