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Lean codes, both banks

mattd
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mattd Enthusiast

mattd

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Check engine lite came on my 2000 Sierra 1500 5.3. 
 

first test at autozone and they guy told me it was fuel pressure regulator. Put a new one on and lite still on. 
 

Oreillys has a better tester that gives more info. It said random misfire and lean bank 1 and 2.  He told me I needed a tune up so got new plugs and wires. Lite still on. 
 

teated again and now it still says random misfire, but repeats lean on 1 and 2 twice. Didn’t record the codes. Proly need to retest to get them. 
 

in the meantime I cleaned the maf w maf cleaner. 
 

it seems to run fine except when I give it Gas to pass it dosent accelerate that well.  But once I started paying attention maybe it is idling slightly rough, maybe. I’m probably thinking too much on it. Idles at 6-700rpm. 
 

Does that point to anything before I start this goose chase?  

mattd Enthusiast

mattd

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Also, when I start it, hot or cold, it chugs at first. Maybe tries to start. Then I let off the key and turn it again and it fires right up. Same sequence every time. 

CamGTP Senior Enthusiast

CamGTP

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Sounds like a vacuum leak.

 

I'd smoke test the intake for leaks. The intake gaskets are a common cause for leaks. Same with the EGR connection on the intake manifold.

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kencar62 Enthusiast

kencar62

Posted
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I had a similar experience and it was failing intake gaskets. They were drawing in air from the galley (underside), so spraying carb cleaner didn't reveal the leak. Replaced the gaskets & the code(s) went away. That issue also took out one catalytic convertor when the ECM kept dumping in extra fuel to fix the lean misfire.

mattd Enthusiast

mattd

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It’s a fuel issue.  pressure tested at 26psi running, and when I just turned the key to ON it jumped up to 20psi and dropped right off back to 0. 
 

when the check engine first came on I took it to autozone and he said I needed a new fuel pressure regulator. They had a weird system where I took reader out to truck. Then they plugged it into their inside computer and it just popped up the parts I needed. No codes, no this is what’s wrong, just buy these parts. 
 

but I did get a new regulator, just it was a $13 one off amazon. Ac delco one is like $70. 
 

ive also replaced the fuel pump a few years ago. Doubt there’s 8k miles on it.  But I’m sure I cheeped out then too. 
 

so which of these to replace first with a name brand?

Edited by mattd
CamGTP Senior Enthusiast

CamGTP

Posted
Posted

Replace the pump.

 

Fuel pressure won't get fixed with a new regulator when it's that low. You can unhook the vacuum line to regulator and see a change but it's not going to bring it back to 50+ psi like you need.

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