PO430, hard starting, sulfur smell in exhaust on 99 Yukon 5.7L

BIKEBUILDER · October 24, 2016

I have a 1999 Yukon wiht 5.7liter. Installed new cat in jan 2106 - the complete pipe unit from Autoparts Warehouse. Over labor day had symptoms of bad fuel pump, which it was so replace that. Started getting PO430 codes and very hard starting and rough idling. Did tune up with plugs and wires and cap, checked throttle body and cleaned it with carb cleaner. Started right up drove like a champ. Two hours later same thing. Hard starting, same code, rough idling and smell of sulfur at times from exhaust. Brother told me probably Fuel injectors. i think cat went bad all of the sudden even though it is brand new.

Any thoughts? Fuel injector pack is expensive. CAt under warranty but on truck and it is my daily driver and to prove to Auto Parts Warehouse I have to pay for a emissions test. Any thoughts?

barry G · October 24, 2016

that is a new world, 4 new sensors to alter injection.

if they can hang on, they will just get cleaner and quieter.

I'd go on with it for some time.. add some tank version of cleaner.

"jet" makes a lubricating type, "heet" is a great cleaner.

on my old truck, the cat has a false code to different brands of o2 sensors... runs perfect. Passes the real cat test, not the code trigger.

anyway,

very sensitive stuff.

93gmc$$ · October 28, 2016

A bad CAT will produce that "rotten egg" smell.

BIKEBUILDER · January 22, 2017

Replaced full bank of injectors and running great for about 3 weeks now same code again only it comes back about every 3 to 4 days or every day? Cat is only year old. I guess O2 sensors replacement?

east3021 · January 24, 2017

Get a scanner to check the oxygen sensors. Also see if it is running rich and check for misfire counts.

Check the wiring at the oxygen sensors, make sure it isn't damaged and shorting out somewhere.

The DTC P0430 is signaling a catalyst inefficiency on Bank 2 but I don't remember if that is downstream of the passenger or driver side. The code may be generated by a bad oxygen sensor, an exhaust leak, bad catalytic converter or misfire/running rich due to injector or ignition issues.

The converters don't usually just go bad on their own, more often a mechanical issue upstream is dumping raw fuel into them and damaging them. That's why the manufacturer will not warranty them without a passed emissions test or some other means of verifying that a separate issue is not damaging them.

I'd start with a scanner and see what the oxygen sensors are doing. You can get an inexpensive Bluetooth Obdii connector and download an app to get most values. DashCommand and CarGauge Pro are two common ones.

Sent from my iPhone using Tapatalk