It's June. That means time to fail inspection again.

[MikeD268]

So my '99 5.3 4x4 Z71 with 298k miles is due for it's annual failure. THOUGHT I was going to escape this year as my previous issues were all resolved and codes disappeared. All 4 O2 sensors were replaced as of the date that I last posted about them. Even have a new wheel hub, brakes and rotors all around. THEN I got ambitious and replaced what I can only assume were the original fuel filter and fuel pressure regulator. NOW, the ONLY code I'm throwing is an 0430. Going to break out the new Actron CP9599 and pull actual live data to see what's going on and will post that later. New cats are apparently "only" $100 +/- but if I can avoid what I can only assume is an awaiting nightmare of crawling under and trying to remove the allegedly offending cat I'd love to. That said, I'm open to any troubleshooting suggestions that anyone may have.

[MikeD268]

So after getting up to temp, I checked out the O2 sensor voltages. Bank1 seems to be functioning well with S1 all over the map and S2 a fairly steady .5-.8 . Bank2 seems to be intermittently faulty with S1 doing it's thing and S2 holding between .5-.8 but occasionally dipping to .1 or .2.

So I guess the questions become, "Is it worth it to:
"Wrestle the cat out, having been in there for 15 yrs, washing it out with either soap/water or sodium hydroxide?"

"Run a gallon of lacquer thinner through the engine with half a tank of gas to see if that will clean things out?"

or just suck it up and buy a new cat circa $100?

Or is there a chance that something completely different is causing this?

[j cAT]

the converter could be coated with carbon etc... removal of the cat and soak in acid for an hour then rise out if it is not broken internally.. this should work to get it to pass for a while. if broken inside just get new one. since you only have this code you should be safe to install new..

when cold starting go under vehicle and put each hand on cat as the engine is warming.. the colder cat is the bad cat they should both heat up at the same rate.

FIRST just to be sure swap the downstream O2 sensors see if your 430 code stays 430 ...if it swaps over then this would be the O2 sensor..

[MikeD268]

Figured I'd revisit this while I had a few minutes. Bottom line is that I'm still waiting for a code to pop after having cleared it with my scanner and filling up with 93 octane. While I may have totally jinxed myself with this observation, I figured the risk was worth it.

"Cheap" gas - banks running lean - poor cat performance - multiple codes set. Cleared codes - better gas - better engine performance. Seems legit, no?

[j cAT]

Originally Posted by MikeD268

Figured I'd revisit this while I had a few minutes. Bottom line is that I'm still waiting for a code to pop after having cleared it with my scanner and filling up with 93 octane. While I may have totally jinxed myself with this observation, I figured the risk was worth it.

"Cheap" gas - banks running lean - poor cat performance - multiple codes set. Cleared codes - better gas - better engine performance. Seems legit, no?

reports have been out that some fuel sold is less octane than stated. 87 could be 85. that would throw off the engine fuel management ..