P0171 P0174 codes - Hello. I'm a newbe here. I first had a check engine light for some knock sensors. I went and replaced those, took off the intake manifold, ...

Hello. I'm a newbe here.

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

Silverado, 2001, 5.3, 4WD

Does spraying brake cleaner around the intake produce a change in engine rpm?

ASTE25 wrote:Does spraying brake cleaner around the intake produce a change in engine rpm?

No change in RPM when spaying the intake.

Also, the P0171 & P0174 code have been on for 3 days, but today it decides to turn off on its own.
I'm confused. Don't know if it will stay off.

I doubt it will stay off since the underlying problem is probably still there.

If you can hear the leak then the lean codes will be back. I'd hold off on the rtv and try to repair it right. If you do end up using rtv, make sure it's high temp.

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. The RTV is high temp.

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

The tube may have gotten bent. The RTV should be okay since you let it cure first.