View Single Post
Bob Kontak Bob Kontak is online now
Fleabit peanut monkey
 
Bob Kontak's Avatar
 
Join Date: Nov 2007
Location: North Canton, Ohio
Posts: 20,862
Garage
Quote:
Originally Posted by dad911 View Post
Bob - p0420
Bet you have a leak downstream of the main cat and before the rear O2 sensor. It confuses the rear O2 sensor because it sniffs false oxygen.

For $120 you can have a small muffler shop weld a sleeve in to snuff the leak, if present. Those guys can do wonders. Even Midas.

I cannot argue with asphaltgambler. You pays your money and you takes your chances.

To expand on P0420, it has to do with the reading from the rear sensor. The front sensor does the real work. It sniffs the raw exhaust and tells the computer if it's rich or lean. The computer adjusts the fuel to offset. When the exhaust exits the primary cat it is sniffed again to see that it's nice and steady with a constant tail pipe ready O2 content. If the readings are outside expected, the code is presented. Air leaks or a cat that is not doing it's job. Maybe a faulty O2 sensor but I would nix that thought initially.
__________________
1981 911SC Targa

Last edited by Bob Kontak; 06-02-2017 at 05:23 PM..
Old 06-02-2017, 05:07 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)