BlueAKSSS Posted May 19, 2010 Report Share Posted May 19, 2010 (edited) My friend just bought a 2003 Silverado 5.3L ext cab that he's rebuilding into an SS clone/style truck. Anyway it's running really bad when you first start it up it idles smooth for about 30 seconds to 1 minute then it starts what I would call "loading up" and missing (shaking truck). Black water dripping out the tail pipes rich smell. Has the original cats, 112,000 miles, haven't tried driving it on the main road yet but just around the neighborhood it instantly starts flashing the check engine light! I pulled the codes and found: P0300 "Random Multiple Engine Misfire" and P0161 "O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 2". What do you guys think is wrong? I'm leaning toward plugged up cats and a bad O2 sensor, but ? Edited May 19, 2010 by Matt* (see edit history) Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted May 19, 2010 Report Share Posted May 19, 2010 My guess would be a bad cat, also count on replacing the passenger rear 02 sensor also..... Quote Link to comment Share on other sites More sharing options...
BlueAKSSS Posted May 20, 2010 Author Report Share Posted May 20, 2010 My guess would be a bad cat, also count on replacing the passenger rear 02 sensor also..... Thanks fireman! Would we have to replace both cats or just the passenger side cat? Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted May 20, 2010 Report Share Posted May 20, 2010 Thanks fireman! Would we have to replace both cats or just the passenger side cat? The P0161 code doesn't mean the passeneger side cat is bad, it just means that the rear 02 on that side is bad. You need to have the backpressure tested in order to see which cat it might possibly be..... Quote Link to comment Share on other sites More sharing options...
Nscott Posted May 20, 2010 Report Share Posted May 20, 2010 Exact same codes my truck through with 50k on it.... Cats clogged (think the driver side was the worst one), I took em both out and wheatley turn of the rear o2's. Love the way it runs now! Quote Link to comment Share on other sites More sharing options...
BlueAKSSS Posted May 21, 2010 Author Report Share Posted May 21, 2010 (edited) Exact same codes my truck through with 50k on it.... Cats clogged (think the driver side was the worst one), I took em both out and wheatley turn of the rear o2's. Love the way it runs now! Thats good to know he was thinking about gutting them, but the truck needs to pass the emissions inspection which consists of plugging in an obd II scanner and checking the codes so I think they might pick up on it. So they will be replaced with magnaflow high flow cats. Edited May 21, 2010 by Matt* (see edit history) Quote Link to comment Share on other sites More sharing options...
Fireman31 Posted May 21, 2010 Report Share Posted May 21, 2010 Thats good to know he was thinking about gutting them, but the truck needs to pass the emissions inspection which consists of plugging in an obd II scanner and checking the codes so I think they might pick up on it. So they will be replaced with magnaflow high flow cats. As long as the codes are deleted and the test is only an ODB test, you can pass with gutted cats as long as they do not perform a sniffer on it. Quote Link to comment Share on other sites More sharing options...
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