0420 & 0430!! Cut em out? No emissions test..

[commercialcobb]

1999 Yukon 210k.. Low efficiency in both banks but in South Carolina we don't have inspections so what kind of problems would I have is I cut them out and welded in pipes? A mechanic told me that Cat's don't just go bad and that it's something in the engine that is causing the problem. I recently did a full tune incl spark plugs, oil, air filter, fuel filter etc. Plus let the Yukon drink some SeaFoam. Ran like a champ for a month but now it has developed a shaking vibration when I come to a stop at idle.. Almost feels like a minor misfire. Its a very light vibration but it's noticable to me.

Is there a common culprit to this?? O2 sensor, coil pak, plug wires, MAF??

Thanks for any help..

 

[SunlitComet]

what brand and part number of plus did you use?

 

[WalterMitty]

I think your mechanic is giving you good advice, also be aware it is a big fine for taking out your cats even if SC doesn't do smog testing.

 

[_Dylan_]

x2 on the plugs.

No you cant cut them out. You have after cat sensors.


If the catalytic converter is clogged you won't even be able to drive it, so doubt they are bad.

 

[commercialcobb]

I was under it the other day fixing the exhaust manifold to pipe leak with a new doughnut and I did not see any sensors behind the cat but I also wasn't looking for one either so I may have missed it. I'll look again.

 

[commercialcobb]

I was right, I found no sensors behind the cats or muffler but did find 2 02 sensors ahead of the Cats... Any way to tell which one may have failed or do I have to replace them both?

 

[_Dylan_]

If there weren't after cat sensors would it throw a code saying the cat wasn't working right?

How is the truck driving? If the cat is clogged it will be down on power and slow.

 

[SunlitComet]

so someone cut your sensors out?

 

[WalterMitty]

I thought the last year for no downstream O2 sensors was 1995.

I have heard of people wiring in an O2 dummy loop. Is there a harness with dummy plugs attached near the outlets of the cats? Maybe tied up somewhere?

 

[commercialcobb]

Hang on, let me go crawl under it again to double check.. I'll take some pics

---------- Post added at 02:27 PM ---------- Previous post was at 02:16 PM ----------

Hang on, let me go crawl under it again to double check.. I'll take some pics

Oh ok, i looked last night with a flashlight and didn't see them but in daylight, there are 2 aft cat sensors that are kind of hard to see but they are there.. So I have 4 sensors, how in Valentines Day am I supposed to know which one has failed?? I am not in a position to replace 4 sensors right now??

Buy one of each, replace right bank and see if the problem goes away. If not replace the right bank and change the left bank and see if that does it?