99 Tahoe advice

[THEFERMANATOR]

From what I see I would find a new shop to go to. Your truck only has 2 cats, NOT 3. Bad vibration from the torque converter? How did he come to that conclusion? I hate seeing receipts like these as most of the time it means they didn't really check anything. The P0420 and P0430 both being in there concerns me the most. I would check the fuel pressure on it to make sure it is up to par. If it was one or the other I could see a bad cat, but both at the same time normally means a fuel delivery problem or an injector issue. How does it start cold? How does it start hot? Do you have problems restarting it hot after it sits for about 10 minutes? To remove the cats there are a few different ways of doing it, but all of them are pretty illegal and the EPA is out for blood here lately over emissions equipment tampering. PM me for ways to disable them for "testing" purposes if you want. Also the P0440 could be the cause of your P0420 and P0430 codes. If the evap purge solonoid is stuck on, then it can cause a rich fuel condition causing it to surge or buck as well as throw cat converter efficiency codes.

[Stinky_Hooker]

I was assuming the third cat was the 3 of 4 oxygen sensors?


I have a guy that will cut my converters off and weld them straight. I had it done on a 2001 s 10. It cause the light to come on but what will it do to my tahoe will it run right? Hell for that matter I can straight pipe it...what will happen?
Would that be what you would do next?


Also I think he came up with the vibration from the torque converter based on driving it and I told him I replaced it.

Thoughts?

[THEFERMANATOR]

This is a 350 or 5.7L engine with a distributor correct? I have never seen one, but I have heard some 99's came with the 4.8 and 5.3L engine. I just want to make sure. As for your O2 sensor, there is one after each manifold, and one after each cat. If you straight pipe it it will go into engine protection mode and limit the timing WAY back. I do NOT reccomend doing it as CAT's aren't that expensive if you get aftermarket MAGNAFLOW universal ones(last ones I bought were $65 each). With the P0440 code, there is a GOOD chance your WHOLE problem is nothing more than a stuck open evaportive emissions valve venting fuel vapors to the engine and fattening out the mixture. This will cause it to be off on the timing tables and show both cats as having poor efficiency.