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P0171 & P01174 - Silverado Running Lean

red_chaser

By red_chaser
in Ask A GM Technician

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red_chaser Enthusiast

red_chaser

Posted
Posted

I first had a check engine light for some knock sensors. I went and replaced those, took off the intake manifold, replaced the seals, cleaned my injectors, and put everything back. Torqued down the manifold screws to 44 in-lbs then 89 in-lbs, put all the hoses back, cleaned the throttle body, and re-installed the EGR hose.

 

The Knock sensor codes cleared and about a day later got new codes, P0171 & P0174. Did some research and it could be a vacuum leak. So I went back make sure everything was on right with some carburetor cleaner and found that the EGR hose had a leak where it plugs into the manifold. I bought a new o-ring gasket and re-installed it, drove it around for a while and the fault cleared.

 

The truck was running nice. Even a rattling nose it had upon hard acceleration went away. Tons of power and acceleration. Two days later the same P0171 & P0174 codes came back. I am at a dead end. Could be the MAF, O2 sensors, injectors, ect, but I don't think that is likely because the truck was running without any codes until I messed with the intake manifold.

 

I can still hear a leak where the EGR hose plugs into the manifold. I am thinking of using RTV around that damn hose. I'm going to take off everthing this weekend and re-install it, maybe I missed something. The pinging noise is back under load.

 

Is ther anything else I could try?

Any advise. Sorry for the long post, I needed to vent.

Does this cause any damage to other compontents? What about the gas mileage?

 

Silverado, 2001, 5.3, 4WD

red_chaser Enthusiast

red_chaser

Posted
  • Author
Posted

The SES light has been on for 3 days straight, but today during my luch break it decides to turn off. I don't know if I should be relieved. Do you guys think it will turn on again? What could be going on?

 

:confused:

red_chaser Enthusiast

red_chaser

Posted
  • Author
Posted

The SES light did come back on.

 

I checked it out this weekend and found I still had a leat at the EGR hose connection at the manifold. I tryed new o-ring gaskets; I even loosened up the EGR valve bracket to facilitate the manipulation of the hose, but that didn't work either. Everytime I sprayed carb cleaner the engine's idle would change.

 

I finally got fed up and put the o-ring gasket with a little RTV, left it over night to fully cure and no more leak! The SES light turned off and the truck runs like new. I hope the vibrations don't loosen it up or the RTV cause something else to go wrong.

 

I hope the SES light doesn't come back any time soon.

 

How else could I have gotten the EGR hose not to leak? That one screw and flimsy aluminum bracket on that hose suck!

  • 3 weeks later...
99gst_racer Enthusiast

99gst_racer

Posted
Posted

I'm getting these same two codes. I plan to clean my MAS and check all vacuum hoses tomorrow. Is there a way to check the functionability of the O2 sensors? I'd rather not replace them unless I can first determine they're in need of replacement.

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