2003 6.0 Vortec rough idle

[ChevSierra1500]

I've got a 2003 GMC Sierra 1500 Denali. Occasionally it will idle rough on start up and when I pull to a stop. It's throwing two codes p0430 and p0431 (cats below efficiency on both banks). One mechanic said there was an exposed wire going to the throttle body. The problem came back recently when the weather started to get cold. Any ideas?

[rjgti]

maf sensor maybe

[ChevSierra1500]

So it's throwing codes p0171, p0174 (running lean on both banks) p0430 (Cats below efficiency on both banks) it seems to idle higher than it should when I start it and too low when it's warmed up. It only does this when it's cold and damp out. Any ideas?

[ChevSierra1500]

Seems like fuel economy has taken a noticeable drop as well

[CoffeyLover]

Unplug your MAF sensor with the engine running. If the idle does not change significantly, you have a bad sensor. Happened to mine a few years back. Easy, cheap fix.

 

If this doesn't work, check your exhaust pressure (you can do this by feel, no special tools needed). I also had a cat get clogged up which caused all sorts of problems. Took me two weeks to figure it out. I went through fuel injectors, fuel filters, wiring harnesses, you name it! I felt a little dumb when I finally took my exhaust off and blew compressed air through it, to no avail LOL.

 

Keep us posted.

[rdnkcpa]

P171 & P174 indicate lean on both banks. If you've been running that way for a while, computer will dump more fuel in to compensate. Look at your fuel trims see what they are at. Your intake manifold gaskets could be shot along with lazy O2 sensors. Check the voltage on them as well.

[efritz]

P171 & P174 indicate lean on both banks. If you've been running that way for a while, computer will dump more fuel in to compensate. Look at your fuel trims see what they are at. Your intake manifold gaskets could be shot along with lazy O2 sensors. Check the voltage on them as well.

99% the cause!!! ^^^^^^^^^^^^^^^^^^

[bradcarveth]

Could it be fuel pump?

 

Sent from my SM-G900W8 using Tapatalk

[rdnkcpa]

99% the cause!!! ^^^^^^^^^^^^^^^^^^

 

And, the 430 is a result of the lean codes. Dumping more fuel in has most likely plugged your cats. Meant to say that in the previous post.