on my 2011 3/4 silverado hd, I have a yellow engine light on. The codes are 174 and 496. MAP and o2 sensor. The only sysmptoms I'm getting are when the fuel cap is removed ther is a vacuum whoosh. The the vehicle is hard to start. Sounds like the evap purge valve. Not sure but never had one cause a vacum. Ive seen pressure, so i guess it could go the other way as well. help
If your EVAP purge valve is bad, it should have also thrown a code. If you would like to test it yourself follow the link below. A hard start is a symptom of a bad purge valve, especially after you fill up at the pumps. http://www.samarins.com/glossary/purge-valve.html
You may want to first repair your error codes before pulling your purge valve to test it. A bad MAP sensor will cause fouled plugs and a rich fuel mixture which could be the cause of your hard start issues. Fix the codes first, then check your purge valve.
Search Chevrolet Silverado 2500HD Questions
Chevrolet Silverado 2500HD Experts
Related Models For Sale
Used Cars For Sale