So I just changed the cat converter along with a new secondary o2 sensor since I had a code for a bad cat converter (P0420) since my car is burning oil. I used a spark plug defouler for the secondary sensor to space it out of the exhaust gas this time around to make sure the code stays off since I don't want to see the code again. Also considering that cat converters and o2 sensors are expensive and I don't want to waste more money on new ones after this, I figure this could work for the P0420 code and would be ok to do since the secondary o2 sensor doesn't affect the air fuel ratio and there are countless threads on other forums on using the spark plug defoulers to solve this code problem.
Well, the P0420 code did not come up again but after going through some drive cycles, usually 2 cycles putting 40-50 miles, I get a P0172 and P0170 which are system too rich and fuel trim malfunction.
I just put in new spark plugs about two weeks ago.
The car has a stock fuel pressure regulator, OBD 2 JDM ITR fuel injectors with 20K miles on them (one of my old fuel injectors were damaged so I replaced them all) and a AEM fuel rail.
I've never gotten these codes before until I put in my new cat converter and o2 sensor about 2 days ago (they have like 150 miles on them).
Other codes prior to the new cat converter were always the P0420 for a bad cat and no other codes.
Car idles fine, drives fine although there is a little hesitation in 3rd, 4th gear around 3-4k rpm with the CEL on. If I reset the CEL to clear the codes, the car drives normal and fine with no hesitation at all, it only hesitates when the CEL comes back on. Normal MPG and no serious bogging at all.
Where should I look first to diagnose?
Could it be bad gas? I only use Shell 93 octane V power though. Bad primary o2 sensor?
I had the same code, P0420. I found out that I had an exhaust leak, a hole in my cat. I took the cat off and welded the hole up and my car was fine. You replaced your cat and sensor so idk where those codes are coming from.