Chevy 2008 Silverado 5.3

Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP. Thank you for your reply and that information as this does help me better understand the situation. I’m sorry to hear you are having this problem. I know this can be frustrating. Please give me one moment to type out some info for you. I’ll be right back! A live optional phone call will be automatically offered by JustAnswer, you can accept or if you decide to decline we can continue with text until you feel the live call would be better suited to you. I will try to help you on this here is the check engine light on ? did you scan it for fault codes? What part was transferred from sensors and pats from the old engine to the used engine? **Please Let Me Know** **Thank You** **Chad Farhat** **ASE Certified Technician**

The check engine light a not onI took it to Christian brothers automotive, so I'm not sure if they did.the old parts were connected to the new used engine

oh I see ,so this just happened The 40 mph stuck tells me you are in limp mode ( lack of power where the engine computer detects major fault and restircted performance ,and that can be caused by several things , Throtle body ,MAF sensor ,Misfire or Trannsmion issues The most common on these silverado is the TB body , now ussualy it willnot comed on used engine ,they used your old one you have to have them recheck it for you

It also revs on its ownWhen it's on driveI'm taking back tomorrow

the revving on its own is another indication of TB body issue

Thanks for knowledge

they need to read the TPS ( throttle position sensor ) voltage that is going from 0 to 5 volts when gas pressed Please Read Below How to Get Back in touch with Me You Can Always Come Back to this Conversation and Ask Me any Follow up Question you May have on this Issue (You can Copy this Link Page & Paste it in your Browser when Ready and it will Open up our Conversation Again) or there should be a Tab on your Screen to Add me As Your Favorite Expert I'm Online Daily from 7 Am Till Late Eastern Time Zone Thank You?Chad Farhat?ASE Certified Technician My goal is to earn a 5 star rating experience. If you have any further questions about this concern, please feel free to reply back to me. If I’m not online at the time, I will respond ASAP when I get back. Thank you for using JustAnswer!