<hr style="color:#000000; background-color:#000000" size="1"> I have a 01 silverado 1500 5.3 just recently my service engine light came on. I had the codes checked and was told it was misfiring on bank 1 and 2. i changed the spark plugs and the light went off. i drove it a few days and the light came back on. i had the codes ran again and i got codes p0171 and p0174 which is bank 1 and 2 system to lean. the guy told me that would be a vacuum leak. he went ahead and cut the light off for me. later i found a vacuum line that runs under the cover that says vortec toward the front. the line had a green cap on it that was loose. i tighten it up but im not sure if i fixed it. any help would be great

 

thats just the evap service port cap and no that wouldn't be the issue, if you have p0171 and p0174 I'd bet on a vacuum leak...more than likely your intake manifold gasket

would check fuel pressure/volume just to be sure or to check for vacuum leak you can find a can of brake cleaner or something similar and spray it around the manifold and see if the engine idle changes

 

thanks man im gonna try that today. now if it is my manifold leaking what would cause that gasket to give away? just from being old or something else?

 

old and/or bad gasket design, if you end up doing the intake gasket make sure you get the permadry gasket set. They're a little more expensive but when it comes to gaskets you get what you pay for