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NO Power 04 GMC 4.3

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Jul 19, 2012, 5:50 PM

Post #1 of 4 (1183 views)
NO Power 04 GMC 4.3 Sign In

04 GMC Silverado
4-3 v6 182000

Check engine light on. P0430 below threshold bank 2, P0300 Random/Multiple, P0101 MAF/VAF (latest code to show).

Began with just the P0430. Truck was running fine so I just put it in the back of my mind. After about 2 wks, light went out. Now, complete lack of power, 0-60 about 30 sec. If I force it, it sounds very throaty like it's in the intake shorkel. I'm suspecting clogged cat bank 2 with such a loss of power. Idles just fine.

This thing normally has plenty of power. Can easily tow my 24 travel trailer all day long. Help please.

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nickwarner profile image

Jul 19, 2012, 6:14 PM

Post #2 of 4 (1173 views)
Re: NO Power 04 GMC 4.3 [In reply to] Sign In

If you don't have a way to test the exhaust backpressure, hook up a vacuum gauge and run at idle. Now rev to 2500-3000rpm. If vacuum drops near zero it almost certainly points to a bad cat.


Jul 19, 2012, 10:20 PM

Post #3 of 4 (1137 views)
post icon Re: NO Power 04 GMC 4.3 [In reply to] Sign In

Exactly right. I just had to confirm my suspecions before taking the leap. Checked, then drilled a few relief holes through the innerds of the cat. Power is back. Now to get a cat replaced. Thanks for the confirmation.

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nickwarner profile image

Jul 20, 2012, 8:42 PM

Post #4 of 4 (1119 views)
Re: NO Power 04 GMC 4.3 [In reply to] Sign In

Thanks for posting the fix and glad you want to diagnose instead of waste money. We're always here for the next repair.

NO Power 04 GMC 4.3

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