2 seperate problems; PO420 and oil leak

[FLSHBCK]

Back in January, I grenaded #4 piston, and now have a freshly rebuilt L67 in my GTP.

Shortly after getting it back together, I found a had a plugged cat, so I replaced it with a ZZP 2.5" catted DP. Now, 7k later, I'm getting PO420. It's basically stock; 0.030 over, I know he milled the heads a shade (no numbers) to straighten them out, stock cam, FelPro head gasket, new stock Delco wires, new Delco 41-101 plugs, etc. Replaced both O2 sensors last weekend, and am still getting the code... any ideas? I know I could get the code deleted, but I'd really rather find what's causing it...

Also last week started leaking a LOT of oil. Losing a quart about every 100 miles. Pulled the flywheel cover off and it's coming from the driver's side front corner of the pan. I redid the pan gasket last weekend as well, and it's still leaking. I'm thinking that's almost got to be rear cover... thoughts on that?

Thanks!

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[bikrboy128]

i had a high flow cat and my car threw p0420 once every few months until i deleted it. there wasnt anything wrong with the cat, just the PCM being pissy.
i would bet the oil leak is from the rear main seal. have fun with that one wnedd:

 

[phat_ridegt]

could be the oil pan or the rear main cover. did you use good rtv on both sides of the oil pan gasket? 1QT/100 miles is a lot of oil....sounds like an oil pan more than a rear main.


the p0420 is because of the aftermarket cat.....you can get an o2 sim or find someone local to delete the code. it doesnt affect the way the car runs at all.

 

[FLSHBCK]

I know the high flow cat tends to cause the code... but per zzp, if everything else is right it should not throw the code, just curious what else might be out of whack before I find someone to delete it for me.

Did use RTV on the pan gasket... and am relatively confident that that is not where it's coming from. With the nose in the air and me laying under it it while it's idling, the oil is coming from the rear corner of the block toward the front of the car, which leads me to think rear cover rather than rear main seal. I suppose it doesn't really matter, as I'll have to pull the motor back out in either case. At the rate it's leaking, gonna have to find time for that soon... LOL

Thanks for the responses!

 

[FLSHBCK]

So it was the rear main seal... rear cover not lined up properly; you could see where one side of the seal was worn down further than the other at roughly 7k miles. Went and bought the J-tools to realign the cover properly and properly press the seal in and all seems to be well.

So who can help with deleting the PO420 code? :smile: